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2 LIBRARY
2 003? Michigan State
University

 

This is to certify that the
thesis entitled

BIOADHESIVES FROM DISTILLER’S DRIED GRAINS
WITH SOLUBLES (DDGS) AND STUDIES ON
SUSTAINABILITY ISSUES OF CORN ETHANOL
INDUSTRIES

presented by

ABHISHEK SINGH

has been accepted towards fulfillment
of the requirements for the

MS. degree in ‘ PACKAGING

 

(7,40% widow flflcfiwfi‘

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12 — J 3 ~ 0? w 9‘

Date

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BIOADHESIVES FROM DISTILLER’S DRIED GRAINS WITH SOLUBLES (DDGS)
AND STUDIES ON SUSTAINABILITY ISSUES OF CORN ETHANOL INDUSTRIES

By

Abhishek Singh

A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
Master of Science

School of Packaging

2007

ABSTRACT

Bioadhesives from Distiller’s Dried Grains with Solubles (DDGS) and Studies on
Sustainability Issues of Com Ethanol Industries

By
Abhishek Singh
Presently, the United States is the largest producer of bioethanol in the world. Currently,
around 7 billion gallons of bioethanol is produced by more than 130 corn-milling
facilities. Dry milling of corn produces ethanol, and coproducts like Distillers Dried
Grains with Solubles (DDGS) and carbon dioxide in equal proportions. Based on
experiments, it was observed that only 1/6th of the entire corn plant is converted to
ethanol, the rest is underutilized or goes to waste. Recent research thrust is to produce
ethanol from the lignocellulose biomass. Bioadhesives derived from DDGS would be one
of the value-added approaches to increase the economic revenues. The DDGS-based
adhesive developed here is intended to be an alternative to conventional starch adhesives.
DDGS was hydrolyzed in an alkali medium, resulting in a brown, viscous and tacky
liquid, referred to here as bioadhesive. One of the bioadhesive formulations had average
lap-shear strength of 127 psi when used to bond paperboard. The mode of failure was
cohesive in nature. The thermal stability of bioadhesive was above 200°C, suggesting
suitability for use over a broad temperature range. The bioadhesive had good
spreadability even at 50% solids content, where as in case of starch even a 10% solution
is too viscous for use. In the present study, aspects such as environmental concerns,
animal nutrition, toxicity were evaluated to find the reasons that limit the scope of its
sustainability. In the context of mounting environmental concerns and due to the fact that

the petroleum resources are fast depleting, it is important to grow the biobased economy.

I dedicate this thesis to my parents and my sister Alpana

iii

Acknowledgements

I express my sincere gratitude to my supervisor, Dr Amar. K. Mohanty for his

invaluable guidance, encouragement and support throughout my master’s research work.

I wish to express my gratitude to my MS committee members for their kind

suggestion and guidance during the progress of my research.

I express my gratitude to Dr M. Misra for her moral support. I wish to thank all
the staff members of Composite Material & Structures Center, Mike Rich, Bob and
Kelby for their help and cooperation. I am thankful to Dr. Mohanty's start-up funding
from Michigan State University and Michigan Agricultural Experiment Station funding
for NC-506 Multistage Research Project. I am thankful to Michigan State University and
School of Packaging for providing the facilities and resources for my research work. I am
thankful to my research group members Dr Wu, Ed, Rahul, Yash, Sanjeev, Vijoya,
Anindo, Dhiraj, Ajay and friends whose support and cooperation contributed largely to
the successful completion of my project. I am obliged to my father Dr C.D.P. Singh, my
mother Kuldeep Singh, Dr I.K. Varma and Dr. Nimisha Agarwal for their constant moral
support.

Fall 2007 (Abhishek Singh)

iv

TABLE OF CONTENTS

 

 

 

LIST OF TABLES ................................................................................ vii
LIST OF FIGURES .............................................................................. viii
Chapter - Introduction - _ 1
1.1 Renewable energy ................................................................................................ 3
1.2 Environmental impact .......................................................................................... 8
1.3 Bioethanol giants ............................................................................................... 12
1.4 Corn milling technology .................................................................................... 15
1.5 Fermentation mechanism ................................................................................... 18
1.6 Corn milling co-products CGM and DDGS ...................................................... 20
Chapter - Sustainability 24
1.7 Is corn sustainable? ............................................................................................ 24
1.8 Need for sustainability ....................................................................................... 24
1.9 DDGS sustainability: limiting parameters ......................................................... 27
1.9.1 High phosphorus ........................................................................................ 27
1.9.2 Flowability aspects .................................................................................... 28
1.9.3 Energy value .............................................................................................. 29

1 .9.4 Mycotoxins ................................................................................................ 30

1.9.5 Carbon dioxide: a green alternative ........................................................... 31

1.10 Resource utilization of corn plant ...................................................................... 34
1.1 1 Economic impact ............................................................................................... 35
Chapter - Bioadhesives _ - _ 45
1 .12 Introduction ........................................................................................................ 45
1.13 Materials and methods ....................................................................................... 47
1.14 Preparation of bioadhesive from DDGS ............................................................ 48
1.14.1 Variation in reagent concentration NaOH and Urea .................................. 48
1.14.2 Effect of pressure ....................................................................................... 49
1.14.3 Effect of cooking time ............................................................................... 49
1.14.4 Effect of filtration ...................................................................................... 50

1.15 Characterizations ............................................................................................... 51
1.15.1 Yield of DDGS bioadhesive ...................................................................... 51
1.15.2 Moisture content measurement .................................................................. 51
1.15.3 Cooking pressure measurement ................................................................. 51
1.15.4 Lapshear strength ....................................................................................... 52
1.15.5 Viscosity measurements ............................................................................ 55
1.15.6 Infrared spectroscopy ................................................................................. 55
1.15.7 Elemental analysis ..................................................................................... 56
1.15.8 Thermal gravimetric analyzer .................................................................... 56

 

 

 

 

Chapter - Results and Discussions 57
1.16 Synthesis of bioadhesive .................................................................................... 57
1.17 Variation in reagent concentration NaOH ......................................................... 57

1.17.1 Curing time characteristics of adhesive ..................................................... 61
1.17.2 Effect of pressure ....................................................................................... 62
1.17.3 Effect of residence time ............................................................................. 63
1.17.4 Effect of filtration ...................................................................................... 63
1.18 Thermal gravimetric analysis ............................................................................ 65
1.19 Elemental analysis ............................................................................................. 69
1.20 Brookfield viscosity ........................................................................................... 69
1.20.1 Brookfield viscosity profile for bioadhesive sample 3N3U ...................... 70
1.20.2 Brookfield viscosity profile for sample 3N3Uatm .................................... 72
1.20.3 Brookfield viscosity profile for sample 3N ............................................... 74
1.20.4 Brookfield viscosity profile for sample 3Natm ......................................... 77
1.21 Fourier transform infrared spectroscopy ........................................................... 80

Chapter - Conclusions 83

Future Recommendations _ 85

References 86

Appendix 1 94

 

vi

LIST OF TABLES

Tablel: Ethanol and coproduct distribution of corn milling technologies (afier ref 35).15

Table 2: Comparison of various co-products in terms of composition (after ref 44) ....... 22
Table 3: Corn plant weight distribution on dry basis (after ref 76) .................................. 35
Table 4: Ear weight distribution on dry basis (after ref 76) ............................................. 35
Table 5: Prospects of the growth of corn ethanol industry (after ref 77) ......................... 38
Table 6: Economic implications of ethanol facilities (after ref 77) .................................. 39
Table 7: Comparative prices of food for year 2006 and 2007, (after ref 79,80) .............. 42
Table 8: Lapshear strength of different bioadhesive for paperboard samples ................... 59
Table 9: Lapshear strength of different bioadhesive for hard maple wood samples ......... 60
Table 10: Effect of alone sodium hydroxide and potassium hydroxide on bioadhesive

yield and lapshear strength for paperboard samples ......................................................... 61
Table 11: Curing time optimization ................................................................................... 61

Table 12: Effect of pressure on the bioadhesive yield and lapshear strength for

paperboard samples ........................................................................................................... 62
Table 13: Effect of residence time on the bioadhesive yield and lapshear strength for
paperboard samples ........................................................................................................... 63
Table 14: Effect of filtration on the bioadhesive yield and lapshear strength for
paperboard samples ........................................................................................................... 64
Table 15: Percent weight loss at different temperatures for natural fibers, DDGS, and
residual fibers ..................................................................................................................... 68
Table 16: CHN elemental analysis of the DDGS and bioadhesive ................................... 69

vii

LIST OF FIGURES

Figure 1: World petroleum consumption pattern (after ref 3) ............................................ 1
Figure 2: US Energy consumption pattern and trends (afier ref 1 I) .................................. 4
Figure 3: US Renewable energy consumption pattern and trend (after ref 11) .................. 5
Figure 4: Recent Ethanol Industry Expansion (after ref 25) ............................................. 10
Figure 5: Historic ethanol production. In the x- axis of this figure, 80 means the year

1980 and similarly, 00 means the year 2000 (after ref 25) ............................................... 11
Figure 6: Trend of ethanol conversion and corn farm yield (after ref 34) ....................... 14
Figure 7: Corn dry milling process for ethanol production (after ref 36) ........................ 16
Figure 8: Corn wet milling process for ethanol production (after ref 36) ........................ 17
Figure 9: Fermentation of glucose to ethanol and C02 by yeasts (after ref 38) ............... 19
Figure 10: North American DDGS Consumption (after ref 25) ....................................... 22
Figure 11: US Crop value for different crops (afier ref 52) ............................................. 41
Figure 12: Historic prices of corn in the US (after ref 52) ............................................... 41
Figure 13: The US leadership in world corn export (after ref 52) .................................... 43
Figure 14: Historic trend of the US com export (after ref 52) ......................................... 44
Figure 15: Recent trend of DDGS production (after ref 25 ) ............................................ 44
Figure 17: Test specimen for lap shear strength ................................................................ 54
Figure 18: Post lap shear testing mode of failure. ............................................................. 54

Figure 19: The setup for curing; (a): Iron bar weighing 22 lbs placed over iron sheet for
uniform distribution of load, (b): Paperboard samples, (c): Lap joint, (d): Iron sheet
placed at top and bottom of samples .................................................................................. 55

Figure 20: Lapshear strength dependence on the alkali concentration for paperboard
samples .............................................................................................................................. 58

viii

Figure 21: Lapshear strength dependence on the alkali concentration for hard maple wood
samples .............................................................................................................................. 58

Figure 22: Effect of alkali concentration on the yield of bioadhesive ............................... 59

Figure 23: TGA plot of weight loss versus temperature for natural fibers, DDGS, and
residual fibers ..................................................................................................................... 66

Figure 24: TGA plot of derivative weight loss versus temperature for natural fibers,
DDGS, and residual fibers. ................................................................................................ 67

Figure 25: TGA plot of weight loss versus temperature for bioadhesive, DDGS, and
residual fibers ..................................................................................................................... 68

Figure 26: Brookfield viscosity profile for sample 3N3U at 50% solid content at room
temperature to 60°C ........................................................................................................... 70

Figure 27: Brookfield viscosity profile for sample 3N3U at 40% solid content at room
temperature to 60°C ........................................................................................................... 71

Figure 28: Brookfield viscosity profile for sample 3N3U at 30% solid content at room
temperature to 60 °C .......................................................................................................... 72

Figure 29: Brookfield viscosity profile for sample 3N3Umm at 50% solid content (SC) at
room temperature to 60°C .................................................................................................. 72

Figure 30: Brookfield viscosity profile for sample 3N3Uatm at 40% solid content (SC) at
room temperature to 60°C .................................................................................................. 73

Figure 31: Brookfield viscosity profile for sample 3N3Uatm at 30% solid content (SC) at
room temperature to 60°C .................................................................................................. 74

Figure 32: Brookfield viscosity profile for sample 3N at 50% solid content (SC) at room
temperature to 60°C ........................................................................................................... 75

Figure 33: Brookfield viscosity profile for sample 3N at 40% solid content (SC) at room
temperature to 60°C ........................................................................................................... 76

Figure 34: Brookfield viscosity profile for sample 3N at 30% solid content at room
temperature to 60 °C .......................................................................................................... 77

Figure 35: Brookfield viscosity profile for sample 3N.“m at 50% solid content at room
temperature to 60 0C .......................................................................................................... 78

Figure 36: Brookfield viscosity profile for sample 3Natm at 40% solid content at room
temperature to 60 °C .......................................................................................................... 79

ix

Figure 37: Brookfield viscosity profile for sample 3Natm at 30% solid content (SC) at
room temperature to 60°C .................................................................................................. 80

Figure 38: FT IR spectra of DDGS, 3N3U and 3N3U...m ................................................... 82

Chapter - Introduction

Crude oil and natural gas are the lifelines of any nation as it satiates domestic and
commercial energy requirements. Fossil fuel dependencies are ever increasing and at this
point of civilization, it would be irrational to expect energy consumption reduction. An
estimate predicts that the world’s energy needs will increase approximately three-fold by
the end of this century [I]. World patterns of petroleum consumption are increasing at
2% growth rate which accounts to a production of 1000 barrels a second [2]. Historic
trends of petroleum consumption are clear from Figure 1 [3]. Realizing energy crisis it is
important to appreciate that energy is one of the most significant parameters to scale the
development of a nation. As a general trend, the more developed a nation is, the more

energy it consumes, estimated by energy consumed per capita.

w a
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Figure 1: World petroleum consumption pattern (afler ref 3)

In analyzing energy consumption key sectors of consideration are transportation,
industrial, commercial and public services, agriculture and residential. Sectoral

consumption of energy suggests that there is huge difference between the developed and

developing nations. As per the International Energy Agency (IEA), it is estimated that
biomass fulfils for on an average one-third of the energy requirements in developing
nations from Africa and Asia. The poor countries have still higher dependencies on
biomass as fuel for heat and cooking purposes [4]. Energy consumption patterns among
various sectors of industrially developed nations, as compared to the developing nations,
suggest that there is huge energy consumption contrast [5]. Typically, for a developed
nation the energy consumptions are higher than developing nations by 10 times in the
transportation sector, 2.7 times in agriculture sector, more than 13 times in commercial
and public services, 5 times in industrial consumption and 3 times higher for residential
energy needs. A striking disparity is observed in the energy consumption that residential
sector energy requirement of developed countries is comparable to the developing
nation’s total energy demand [5]. Per capita energy consumption is a significant
parameter to estimate degree of development. Comparing three classes of development
also suggests contrast. In poor countries, an average person survives on less than one
barrel (5.6 gigaJoules) of oil equivalent per year. A person in the developing nation
utilizes the energy equivalent to 6 barrels of oil (34 gigaJoules) on annual basis. Whereas
the average person in the developed world can afford to spend nearly 40 barrels of oil

equivalent (220 gigaJoules) [5, 6].

On a broader perspective, energy consumption trend suggests that the more
developed a nation is, the higher is the energy consumption. However, correlation of
nation’s wealth to its energy consumption does not always go hand in hand; the energy
efficiency can add contrast to this relation. To exemplify, consider nations Japan and

Norway, though Japan has slightly higher per capita income, USD 35,620, but due to

fewer local resources of energy generation, there is more efficient energy usage therefore
lower per capita energy consumption (150 GJ). Whereas for Norway there is plenty of
cheap hydroelectricity resources therefore, even with slightly lower per capita income of
USD 34,530 the per capita energy consumption is 250 gigaJoules [7] . As regards to
energy, petroleum is the most popular energy source, common to all nations. Again the
industrial technologies prevalent in developing nations are more energy intensive than

their developed competitors.

1.1 Renewable energy

Renewable energies are those that either are renewable natural resources or
inexhaustible by source. The classification of renewable energy includes biomass energy,
hydroelectric, solar, wind, and geothermal. Among all contributor to the world energy
economy, biomass is the fourth largest after oil, natural gas and coal [8]. Biomass holds
the potential to produce a variety of energy forms viz. electricity, fuels in solid, liquid,
and gaseous states, and heat, as well as chemicals and biobased materials. In United
States by 2004 about 100 quadrillion Btu of total energy was consumed and it is
projected that the energy demand in the following two decades is likely to increase up to

131 Btu [9].

As per vision 25x25 the United States targeted to produce 25 percent of its energy
from renewable resources by the year 2025 [10]. By 2004 the total share of renewable
energy is little more than 6 % while fossil fuels account for 80 % of energy requirements.
From Figure 2 and Appendix 1, it is clear that the contribution of renewable energy has

been steady during the early half of this decade [1 1]. Among fossil fuels coal and natural

gas has contributed more or less by equal amount and petroleum accounts for about 50 %
of fossil fuels. However, among renewable energy sources more than 90 percent is
obtained from biomass and hydroelectricity as shown in Figure 3 [11]. Renewable fuels
are blessed to be sustainable and environment friendly, however their commercialization
has invariably struggled because the technology to harness the energy is expensive. Let

us have the general understanding of various renewable modes of energy.

9 Total I Foeeil fuels A Coal
a Natural Gas 0 Petroleum x Renewable
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Figure 2: US Energy consumption pattern and trends (after ref 11)

l Hydroelectric
III Geothermal
l Biomass

I Solar Energy

I Wind Energy

 

Energy (Q BTU)

A

 

2000 2001 2002 2003 2004

Figure 3: US Renewable energy consumption pattern and trend (after ref 11)

Renewable resource based fuels such as com-ethanol and biodiesel are required to
develop as alternative resources to cater the energy need. Ethanol accounts for 99% of all
biofuels in the United States (US) [12]. In 2004, 3.4 billion gallons ethanol was produced
which grew to 4.4 billion gallons by February 2006 [13]. Nearly 5 billion gallons of
ethanol as produced by end of 2006 could displace about 3.57 % of 140 billion barrels of
consumed gasoline sold by volume and 2.38 % in terms of energy [14]. The predominant
source for ethanol in the US is com. Corn based ethanol is used as gasoline additive
resulting in a cleaner-burning fuel with higher-octane value. In the US, corn is the
primary feedstock for ethanol production. In 2006, about 18 percent of the total US corn
crop was converted into ethanol. This corresponds to approximately 1.43 billion bushels
[15]. Other potential sources of ethanol are grains like sorghum and lignocellulosic
biomass such as cr0p. residues viz. corn cobs, comstalks, wheat straw, rice straw, switch
grass, prairie grass and vegetable and forestry waste. Ever increasing differences
between demand and supply led to serious amendments in regulations of fossil fuel’s
production and distribution. The energy bill in August 2005, which falls under Energy
Policy Act of 2005 makes mandatory use of renewable fuels as blends in automobiles
[l6]. Repercussion of political and economic decisions in favor of adoption of renewable
fuels, especially corn based ethanol, ensures steady and promising growth of the com-
ethanol industry which serves as catalyst to tackle nation’s energy security challenge

[17].

Depleting petroleum sources is not the only bias in attempts to replace gasoline,
another critical factor of concern is environmental. Fossil fuels like gasoline and diesel do

not burn as cleanly as ethanol or hydrogen. With prevailing technologies, we cannot

generate enough hydrogen fiiel to meet energy needs. However, ethanol has emerged as
an immediate rescue to the energy crisis. Biofuels like bioethanol and biodeisel helps
reducing greenhouse gas emissions from vehicles. The need for higher-octane value,
clean burning components and a substitute for methyl-tert-butyl ether (MTBE) in
gasoline has created a niche market for ethanol as an inescapable constituent in
automobile fuels. MTBE is added to gasoline as an oxygenate that increases its oxygen
content and octane value. However, on the dark side, MTBE is known to pollute soil and
water [18] ; therefore MTBE is gradually being phased out. In the United States,
legislation to abolish MTBE has been enforced on an individual state basis. Since July
2005, 25 states in the USA have banned MTBE for being major ground water pollutant
[19]. Incorporation of ethanol into gasoline as an oxygenate and octane value booster
bears the lirrritation that the distribution and storage process invariably gets contaminated
with water. The water contaminated ethanol blend of gasoline suffers from the phase
separation of ethanol and gasoline due to the fact that ethanol finds preferential solubility
in water and that water is immiscible to gasoline. The formation of these two phases
results in improper burning of the fuel mixture. Petroleum hydrocarbons belong to the
chemical category of alkanes, alkenes, aromatic compounds and their derivatives. Such
hydrocarbons are chemically hydrophobic and exist in a phase separated from the water;
since ethanol has hydroxyl functionality, it has substantial affinity for water. Therefore,
ethanol segregates from the gasoline into the water. Consequently, ethanol is transported

and stored separately until delivery to retail stations [20].

1.2 Environmental impact

Increasing energy demands drive higher consrunption rates of fossil fuels.
Emissions from burning fossil fuel increase the carbon dioxide concentration in the air.
Carbon dioxide is a greenhouse gas that traps solar heat and contributes to global
warming. Global warming not only makes polar ice liquescent, but also affects aquatic
life. Thermally-limited oxygen delivery shows close match with environmental
temperatures. Exceeding this temperature limits the growth, performance and abundance
of marine species [21]. Zoarces viviparus is a bioindicator fish whose population declines
due to temperature rise. This fish is used for monitoring the effect of global warming in
the North and Baltic seas. The greenhouse effect is responsible for the rise in
environmental temperature. Factors that contribute to global warming are population;
sophisticated living standards, which demands extra electricity and equipment; increased
growth in industrial output and increases in transportation and travel [22]. All such
factors show ever increasing dependence on coal, gasoline and natural gas for electric

power generation.

As regards the greenhouse emission considerations, it is critical to evaluate
quantum of such air pollutants are present in the system and their relative proportions.
Annual assessment of greenhouse gases and their sources help us understand and predict
the impact of such activities and resources on the environment. Below are shown

proportions of various greenhouse gases and their relative discharge to the atmosphere

In 2001, it was observed that in the US as a whole electrical power generation that
produce most of the C02 emissions (39%) followed by the transportation sector (32%),

industrial (18%) , the residential (6.4%)and the commercial sector (4.6%) [23].

Emissions data are expressed in C02 equivalents where the carbon dioxide
equivalent refers to that weight of carbon dioxide that would produce equivalent radiation
absorption i.e. equivalent trapped thermal energy. Carbon dioxide equivalent data can be
converted to carbon equivalents by multiplying by a factor of 12/44. Equivalence for
greenhouse gases like methane and nitrous oxide is expressed in C02 equivalent units by
multiplying their emissions (in metric tons) by their global warming potentials (GWP).
Global warming potential (GWP) is a measure of the absorptive power of heat of
greenhouse gases in the atmosphere. GWP conversions of each gas are relative to that of
carbon dioxide (C02), as well as the decay rate of each gas from the atmosphere. Thus,
GWP helps in estimating various green house gases using a common scale [24]. The hunt
for dependable sources of energy has culminated into valorous petroleum explorations
and state of art refineries from downstream processing. However, it was myopic vision
that sustainability factor was ignored since the crude oil became backbone of our energy
needs. To meet our energy surge of modern civilization we must develop our alternate
sources and most importantly renewable ones. Earnest efforts towards renewable fuel are
reflected in the phenomenal growth of ethanol industries in the US and the exponential
increase in ethanol production as shown in Figure 4 and Figure 5 respectively [25]. The
production of ethanol has shown significant increase over past two decade for 1980 to
1989 growth rate was 83 % however early 90’s showed slight decrease however gained

momentum towards the later half of the decade and having over growth rate of 53% for

the decade. However, for the past 4 years there has been an exponential rise in with the
growth rate having linear equivalence of 500%. Alarming global wanrring as set forth by
automobile exhaust demands for greener fuels. Bioethanol has therefore emerged with

commercial endeavors to meet environmental needs.

  
   
  
   
  

     
    

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Figure 4: Recent Ethanol Industry Expansion (after ref 25)

10

 

 

 

 

 

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Figure 5: Historic ethanol production. In the x- axis of this figure, 80 means the
year 1980 and similarly, 00 means the year 2000 (after ref 25)

Ever depleting non-replenishable fossil fuel resources, we are not only facing
glimpse of energy crisis but also leaving a bleak firture for generations to come.
Appreciating the need of an hour, it’s wise to make hay while the sun shines. Shifting
gears from petroleum refining to biomass refining will significantly reduce both
greenhouse gas emissions and the extent of non-renewable resource depletion. By
reducing U.S. dependence on foreign oil and the military investment associated with this
dependence, large-scale biomass refining would ensure nation’s energy security. Rural
economy boost is realized by creating a large market for energy crops that could
potentially balance demand for agricultural products with current production capacity

[26].

11

1.3 Bioethanol giants

Market of bioethanol as fuel is dominated by Brazil and followed by the US.
Together Brazil and the US produce about 80% of world’s total ethanol. Like Brazil, the
US produces fuel ethanol from agriculture crops. Brazil utilizes sugarcane while the US
ferrnents ethanol fuel from corn. Comparative study of two bioethanol giants suggests
that crop type and fraction of crop that goes for fuel production dictates the ethanol
market share and market growth rate. Brazil cultivates sugarcane on 6.2 million hectares
with a yield little more than 422 million tons. Over 50% of sugarcane produce is
dedicated for ethanol production while remaining goes for sugar production to suffice
domestic needs and export [27]. Brazil produces 4.45 billion gallons and ranks second to
the US which produced 4.9 billion gallons of ethanol in year 2006. Brazil contributes 38
% while the US contribution is 41% of world ethanol production. In contrast to Brazil,
the US, produced 273 million tons of corn of which 45.81 million tons were utilized for
making ethanol. Fossil fuel prices hike and its depleting sources were the driving forces
for Brazil and the US to adopt renewable fuels. Brazil faced the oil crisis in early 70’s,
and therefore, launched a national program of alcohol (PROALCOOL), in 1975 [28]. In
the world context, Brazil is the first nation to adopt firel ethanol as renewable automobile
fuel. Presently in Brazil, 80% of non-diesel vehicles have flexible fuel internal
combustion engines. In Brazil, bioethanol fuel is used in 40% of total non-diesel
automobiles [29]. Brazil has been using ethanol in automobiles as early as 1930, the
growth rate of sugarcane ethanol in Brazil had been phenomenal this decade, produced

192,000 barrels a day in 2001 which rose to 282,000 barrels a day in 2005. Brazil

12

government, ministry of agriculture is optimistic on ethanol production to reach 442,000

barrels a day by 2010 [29].

In Brazil there is an extensive ethanol distribution network having a record
number 32,000 ethanol filling facilities. In contrast USA, has about 1166 gas stations that
sell the E85 blended fuel [27, 30]. United states have more price fluctuation in corn and
subsequent ethanol production. Such volatility in ethanol pricing has opportunities for
Brazil to capitalize; one of the bunting examples refers to the ethanol export from Brazil
to US dated back October 2005, that time Brazil’s ethanol production cost was $ 0.83 per
gallon while that in US was $1.09 per gallon. Domestic market selling price for Brazil
and US was $1.38 per gallon and $2.47 per gallon for the same month respectively.
Brazilian ethanol on adding the import tariffs and freight cost $2.12 per gallon, which
was $0.35 per gallon cheaper than the contemporary cost of ethanol in US. Such a huge
price difference allowed Brazil to export 5.2 million gallons of ethanol to US [31]. In
contrast, the US, owns a reputation of being world largest producer and consumer of
corn. In the year 2006/07, by August, the US corn production was 278.797 million metric
tons against world’s total of 689.313 million metric tons. As regards consumption in
2006/07, US consumed about 245.503 million metric tons of corn against world’s
consumption of 723.476 million metric tons [32]. As regards world production and
consumption, the deficit was met by previous year’s stocks. In the US, com-ethanol is
derived fi'om field corn which is cultivated as conventional corn and genetically modified
(GM) corn. Conventional corn is easily attacked by pests and affected by weeds and thus
its yield is limited. To overcome such cultivation issues, GM corn species were

developed that had resistance to pests and weeds. In the US, major genetically modified

13

corn varieties cultivated are Bacillus Thuringiensis (BT), herbicide tolerant (HT) and
stacked genes varieties [33]. These genetically modified corn accounts for more than half
of the planted corn crop. Historic data for yield per acre of corn crop suggests that there is
an increase in the corn yield per acre. Increment in the corn yield is due to the advent of
hybrid varieties of corn. Agriculture technologies have evolved over a period of time
resulting in an efficient recovery of harvested grain which otherwise goes in vain due to
damage caused by insects and herbs along with harvesting losses. Figure 6 shows
historic growth trends of fermentation and corn yields [34]. In case of ethanol conversion
the growth rate is not so contrasting as enzyme modification is limited. Growth in
fermentation technologies has been sluggish with little improvement over a period. From
the Figure 6 it can be seen that there is mere 17% growth rate in conversion efficiency. At
this point it is important to understand the corn milling processes that has actuated the

corn ethanol revolution.

 

 

 

4 _ I Ethanol conversion(gal/bu) ~-- 200
o Yield(bu/acre) 1 71
g 160.4 9 A
E O 3.36 g
2 -3 ~ 13866 f 150 g
r: 3 I .a
g g’ 2,4 - 2.72 E
a a o 2.52 g
v >
5 2 ‘ 106.7 10° E
g u“!
1 “1‘—‘““—-‘_‘""T r ‘ I 50
1980 1990 2000 2010 2020
years

Figure 6: Trend of ethanol conversion and corn farm yield (after ref 34)

14

1.4 Corn milling technology

In the US, presently, two main technologies are adopted in corn milling and
subsequent fermentation into ethanol i.e., dry milling and wet milling. Both technologies
differ in processing conditions and co-product yields. Ethanol and co-product distribution
is discussed in Table l [35]. In US at present, around 82 % of ethanol production is done
using dry milling of com [36]. Dry milling process comprises of sequential steps of
grinding, saccharification, fermentation and purification. The main product of dry milling
is ethanol and associated co-products are distillers dried grains with solubles (DDGS) and
carbon dioxide. The predominant choice of dry grinding is due to simpler processing and
relatively cheap equipments. Wet milling is the process of separating the corn kernel
into starch, protein gluten, germ, and fiber in an aqueous medium. Ethanol is the
main product of wet milling while various co-products are corn gluten meal (CGM), corn
gluten feed and mixtures of sugars. Various steps involved in this technology are shown
in Figure 7 and Figure 8 respectively [37].

Tablel: Ethanol and coproduct distribution of corn milling technologies (after ref

35)

 

 

 

 

 

Process/Products Dry Milling Wet Milling
Ethanol (gal) 2.7 2.5
DDGS (lbs) 18 -

CGM (lbs) - 2.5
C02 (lbs) 18 18

 

 

 

 

 

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1.5 Fermentation mechanism

Commercially, yeasts predominantly perform ethanol fermentation. Saccharomyces
cerevisiae, an anaerobic microorganism, is the most important species that is used in
making ethanol. In the fermentation industries, ethanol is obtained mainly by anaerobic
breakdown of glucose using these organisms. The reaction pathway of glycolysis is
named as the Embden-Meyerhof-Parmas pathway, as shown in Figure 9 [38]. The
process of glucose fermentation by the yeasts is mainly the glycolysis process with
additional steps of decarboxylating pyruvate to form acetaldehyde using pyruvate
decarboxylase, then reducing acetaldehyde to ethanol using alcohol dehydrogenase. In
the whole process, there are two moles of adenosine triphosphate (ATP) net gain per
mole of glucose. The final steps are mainly carried out to recover the used nicotinamide

adenine dinucleotide (N AD) in the previous step and thus produce ethanol [39, 40].

18

Gl
ucose 2 ATP

2 ADP
Frutose 1, 6-biphosphate

fructose biphosphate aldolase
2 [glyceraldehyde 3-phosphate]

2 NAD '
‘ 2 Pi
2 NADH + IF ’ Glyceraldehyde 3-phosphate dehydrogenase
2 [1, 3-biphosphate glycerate]

2ADP
I 2...

2 [3-phosphoglycerate]

3-phosphoglycerate kinase

phosphoglycerate mutase

2 [2-phosphoglycerate]
H20 3 l enolase

2 [phosphoenol pyruvate]

2ADP

vate kinase
2 ATP pyru

2 [pyruvate]
@ 2 (302 pyruvate decarboxylase

2 [acetaldehyde]

2 NADH + I-F
alcohol dehydrogenase

2 NAD

2 [ethanol]
Figure 9: Fermentation of glucose to ethanol and CO2 by yeasts (after ref 38)

19

1.6 Corn milling co-products CGM and DDGS

In contrast to lignocellulosic biomass, easily ferrnentable sugars from corn have
made it a niche feedstock for ethanol production; however, conversion of corn into
ethanol is limited to 2.8 gal / bushel[34]. Presently bulk of DDGS produced is consumed
for fauna feed as shown in Figure 10 [25]. DDGS as animal feed does not provide enough
value addition, and the phenomenal growth of ethanol industry is generating tremendous
amount of DDGS that will surplus of animal feed requirements. Presently revenues
generated by DDGS priced for $ 80-$120 per ton as animal feed accounts for 15-20 % of
total revenues of an ethanol plant[4l]. Besides animal feed, value added application of
DDGS, would lead to high economic returns. DDGS is a rich source of zein protein.
Zein protein is used for encapsulating essential oils such as oregano, red thyme and
cassia, these oils have antimicrobial properties. Extremely small zein-coated particles are
designed for controlled delivery system. This minimizes the interactions of essential oils
with other components in the food [42]. In many instances, in order to obtain the desired
inhibition, an excess of oil is required which results in poor economics and a number of
undesirable effects. As a neutraceutical application, a group of corn tripeptides present in
DDGS, was reported to inhibit the angiotensin converting enzyme (ACE) and therefore
helps lowering of blood pressure. Also, certain corn penta peptides have been reported to
have herbicidal activity; as the penta peptides act as toxins to common weeds. Literature
suggests that larger basic peptides, isolated by acid extraction from corn kernels that
exhibit antimicrobial properties[43]. The development of new antimicrobial peptides is of
practical importance as a result of increasing levels of bacterial resistance to antibiotics

due to overuse in humans and livestock.

20

Another co-product of com-wet milling is Corn Gluten Meal (CGM). Table 2
compares DDGS and CGM in terms of their relative nutrient composition[44]. Primary
use of CGM is animal feed. Corn gluten meal is richer in protein content than DDGS. It
is a potential natural herbicide. Corn gluten meal has a physical state of a non-volatile
powder, in its granular state CGM retains its state of aggregation and does not spread
away. Corn polypeptides due to their characteristics allow selective control and
application of CGM as a pesticide and herbicide. CGM is effective in established lawns,
where it hampers root growth in weed seedlings. CGM is targeted to control pests like
crabgrass, redroot bigweed, creeping bentgrass, purslane, smart weed, bennuda grass,
dandelions, lambs quarter, barnyard grass, and foxtail [45]. As regards the whole corn
plant, we are able to convert only a small portion of total, rest is again a agricultural
residue. In order that com ethanol industry to flourish, there should be maximum use of

corn plant.

21

Table 2: Comparison of various co-products in terms of composition (after ref 44)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

High Quality
Nutrients U.S. Corn €01,122?“
DDGS

Crude protein, % 30.6 66.9

Crude Fat 10.7 3.2

NDF eutral
(N 43.6 9.7
Detergent Fiber)
ADF (Acid-
11.8 5.1

Detergent Fiber)

Lysine 0.83 1.13
Methionine 1 .13 2.3 l
Tryptophan 0.24 0.34

Calcium 0.06 0.06
Phosphorus 0.89 0.44
Poultry Swine

3% 9%
Dairy

. 46%

   

Figure 10: North American DDGS Consumption (after ref 25)

22

It is noteworthy that utilization of grains and oils for energy generation or
chemicals is commercially viable, however at a cost, which is their unavailability for use
as food or feed. Remains of the cr0p plant after harvesting grains and oils such as stover
and straw are promising sources of biomass and brighter side of the story is that their use
does not compromise the supply of food. Corn ethanol faces criticism for kernels that are
feeding automobiles can instead be food for more than 2 billion world malnutrition
population [14]. Non food corn stover is the leading candidate as a biomass source to
support a lignocellulosic biorefinery because of large quantities available. As per an
estimate in year, 2003 in USA there is a potential supply of between 60 to 100 million

tons of corn stover per year [46].

Summing up, Brazil and the US ethanol scenario, although the US is largest ethanol
producer, yet its energy independence is a distant goal. Brazil enjoys energy
independence is due to reasons such as nature of feedstock, cheaper production rates and
energy efficient residue endues. As regards the feedstock considerations sugarcane scores
far ahead than corn. 0n the energy grounds net energy returns are 1.3- 1.8 for corn
whereas for sugarcane the energy returns is 8.3 [47] Such high values of energy returns
are obtained due to the fact that bagaasse which is burned to produce electricity and meet
energy demands of ethanol plant. Another factor of consideration is that sugarcane yields
twice more volume of ethanol obtained per hectare than com [48]. On a concluding note
Brazil counts upon sugarcane coproduct energy returns this allows cheaper ethanol
production rates. In the US, corn ethanol coproduct DDGS, has poor fuel value as it rich
in proteins. However, biobased products derived from coproducts shall generate enough

economic returns that help in lowering manufacture cost of ethanol.

23

Chapter - Sustainability

1.7 Is corn sustainable?

Sustainability is a comprehensive rating factor that decides the overall
acceptability of a system. Sustainability can be understood as an ecological coherence
with the associated technology and capital Sustainability assessments are gaining
popularity in estimating the system’s impact on the environment, its commercial viability
and future prospects. This study is a partial fulfillment in order to evaluate the
sustainability of Distiller’s Dried Grains with Solubles (DDGS). In the US, bioethanol is
derived from corn. As a national pride, the US owns this reputation of being the world’s
largest producer of not only corn but also bioethanol derived from the same. Corn has
faced criticism over the net energy returns in producing bioethanol. Technology
advancement made upstream and downstream processing energy efficient thereby
improving net energy returns. Again, in order to address the issue, sustainable corn
ethanol demands further rigorous assessments in terms of environment friendliness and
economy. Presently, ethanol derived form corn receives a subsidy of $0.51 per gallon to
sustain its market [49]. The higher cost of ethanol is primarily due to the corn grain price
followed by fossil fuels required to run the plant. Coproducts such as DDGS and carbon
dioxide (collected by some ethanol plants), are produced by the dry milling of com are
sold cheap, resulting in little revenue returns. DDGS has a trade value of 3-5 cents a

pound [41].

1.8 Need for sustainability
The necessity to evaluate the sustainability of coproducts is evident from the fact

that in order for corn ethanol to be sustainable, every component associated should

24

individually be sustainable. It would be irrational if corn ethanol was sustainable while
the coproducts were unsustainable. Therefore, the coproducts and their related processing
should be modified to qualify there status as sustainable. This sustainability study of
DDGS emphasizes upon defining the criteria for sustainability and identifying those

factors that hampers the scope of DDGS as sustainable feedstock.

To our present consideration, system refers to the corn dry milling ethanol plant,
ethanol as the main product, with DDGS and carbon dioxide as its co-products.
Sustainability issues regarding the value addition of co-products (DDGS) of the corn
ethanol industry can be best understood while considering the system in totality. To be
sustainable, DDGS should contribute to the biobased economy, besides having its end use
in harmony with the environment. DDGS is produced in plenty and is therefore a
potential resources for food and new biobased materials. Apart from raw material
support, the value addition of co-products provides an economic support that strengthens
long-term commercialization prospects. The under utilization of co-products does not
contribute to their full potential to the economy or even worse, can raise environmental
hazards thereby weakening environmental friendliness and sustainability at large [50].
Value additions of DDGS in terms of biochemicals, biobased materials and energy will
reinforce the economy of corn ethanol production. However, it is explicit that processes
related to value addition should by themselves comply with the criteria of sustainability.
Unmanaged DDGS is a potential environmental hazard; therefore it is an important factor
that can limit the production of ethanol form corn and amount of corn to be cultivated. As
long as the upstream compliments the downstream processing of corn to produce ethanol

and does not harm the environment, the industry grows in a sustainable manner.

25

Moreover, crop cultivation requires huge machinery that runs on fossil fuels. Corn
cultivation requires fertilizer and fuel to run machinery as nomenwable inputs. A
petrochemical such as urea is an inevitable nitrogen fertilizer; however its use can be
optimized by crop rotation. Integrating the nutrient cycle including nitrogen fixation
improves the efficiency of corn cultivation [51]. Moreover, the fuels that run the
machines can be blended and eventually, replaced with renewable alternatives such as
ethanol and biodiesel. Crop transportation also demands fossil fuel inputs; transportation
fuel once being renewable shall raise the energy returns from corn ethanol. Among
fertilizers, cultivation machinery and transportation vehicles, it is relatively easier to
introduce renewable firels in the transportation system. The value addition of co-products
and the efficient bioethanol conversion process do extend the domain of corn
sustainability, but in a limited manner. The bulk demand for ethanol can be met in a
sustainable fashion only by lignocellulosic feedstocks. Resource utilization is related to
the economic aspect of sustainability. With given material inputs it is important to have
minimum waste generation. In this study, the focus is limited on the co-products DDGS
and C02. From Figure 10, it can be seen that the limited consumption of DDGS as swine
and poultry feed is indicative of DDGS related issues in animal feed. Before evaluating
DDGS as feedstock on nutritional grounds, it is important to understand the composition
of corn kernel. Typically, a mature corn kernel contains about 61 % starch, 19.2 % crude
protein and fiber, and 3.8 % fat [52]. Such corn kernels lose starch after fermentation
while protein, fat and fibers remain. The undigested part of the corn afier dry milling is
referred to as distiller’s grain, this fermentation residue is mixed with the concentrate of

the thin stillage to produce DDGS. The co-product DDGS is rich in protein and fat.

26

Typically, protein, fibers, fat and other nutrient concentrations are increased up to 3-4
times than that in original corn kernels. DDGS is typically rich in amino acids such as
Lysine, Methionine, Cystine, Threonine, Tryptophan, Arginine, Isoleucine, Valine and
Leucine [53]. DDGS also contains macro mineral content such as phosphorus, potassium,
magnesium, sodium and calcium [54]. Unlike proteins, amino acid concentration in
DDGS decreases than that present in corn. The reason for this decease is due to the
thermal degradation during the drying cycle. The price of DDGS is governed by
phosphorus levels, lysine content, and metabolizable energy content [55]. The issue
associated with the color of DDGS is important as it is correlated to the amount of
available amino acids in particular lysine. The lighter the color better it is in terms of

amino acid concentration. Therefore, the drying of DDGS affects product acceptability.

1.9 DDGS sustainability: limiting parameters

DDGS goes as a nutrition supplement in animal feed. Issues that govern the scope
of sustainability for DDGS as identified include high phosphorus content, energy returns,
mycotoxin contamination, flowability issues, lack of standardized testing and inconsistent

product.

1.9.1 High phosphorus

Among DDGS, corn and corn gluten meal, the former has highest concentration
of available phosphorus. In a research study, formulations were prepared by varying the
amount of DDGS in the feed ranging from 0 to 40 wt%. With 40 wt% of DDGS in the
diet there was an increase of more than 55% in the phosphorus content [56]. As such,

there is no commercial process to extract phosphorus from DDGS in a cost effective

27

manner. Therefore, the amount of DDGS in the animal feed has to be regulated. A DDGS
rich diet results in a manure rich in nitrogen and phosphorus. However, the amount of
such manure when applied based on nitrogen content leads to an excess of phosphorus
concentration in the soil. This excess phosphorus gets carried away to water bodies (both
surface and ground) this process is called eutrophication [57]. Higher levels of
Phosphorus in water affect the aquatic life, therefore disturbing the ecological balance. If
however, when manure is applied based on the amount of phosphorus, the required
nitrogen levels are not met. Amount of Phosphorus that goes in the manure of non-
ruminats can be controlled by making it more digestible in the diet. Phytase, an enzyme,
which when added in the feed along with DDGS can increase digestibility of phosphates

in pigs by maximum of 60-65 % [58].

1.9.2 Flowability aspects
One of the critical issues associated with the storage and handling of DDGS is its
ability to flow. In 2005, about 52% of total DDGS exports were sold to Ireland, Spain,
Mexico and Canada while the remaining was exported to countries such as Thailand,
Germany and Indonesia. The exports of DDGS from the US is increasing, there was an
observed 26% increase in exports from 2004 to 2005 [54]. The trade and transit of DDGS
' requires bulk storage and handling. DDGS upon storage tends to agglomerate and does
not flow easily. DDGS has a bulk density range of 389 to 496 Kg/m3 and has an angle of
repose ranging from 26 ° to 34 ° that leads to arch formation inside bins and silos, which
hampers its flow outward after storage. DDGS when stored in bins and silos have a
tendency to form an interlock i.e. a bridge formation that prevents the free flowing of

DDGS particles. DDGS particle size span a range of 127 micrometers to 1100

28

micrometers. The average particle size for DDGS falls below 600 micrometers [59]. Such
small particle sizes are responsible for the characteristics of such hindered flow.
Moreover, as the soluble content in DDGS is increased, the particle size increases and
also affects pelletizability [60]. In the US, animal feed is palletized, and since DDGS
does not easily palletize, this proposes obvious problem [61]. Together, the inability to
palletize and the poor flowability of DDGS affect its transportation and trade at large.
Several flow enhancers such as aluminum silicate, silica and calcium stearate have shown
significant flow enhancement in sucrose, lactose and modified cornstarch. Such flow
enhancers are likely to enhance the flowabilty of DDGS. The mechanism of flowing aid
is that it sticks to the substrate by means of secondary forces and produces smooth
boundaries. Also they fill the inter grain voids. However, these quantities are typically
added up to 2% to 3 % [62]. Higher quantities may have antagonistic results. Results of
decreased caking and flowability were observed in calcium carbonate [63], mango

powder using tricalcium phosphate, maltodextrin and glycerol monostearate [62].

1.9.3 Energy value

DDGS by composition averages around 50% carbohydrates including starch,
cellulose, simple sugars. This makes DDGS a potential boiler fuel. DDGS has 9860
BTU/lb of thermal energy. As compared to DDGS, propane has 2.5 times more calorific
value. However, when compared to the cost of fuel, DDGS is a lot cheaper and offers net
energy savings. One proposed method is to burn DDGS in a biomass burner and obtain
the thermal energy. This energy is utilized in making the process steam and running
dryers. In a case study [64], the DDGS was evaluated, as fuel to meet the energy needs to

run an ethanol plant. It is estimated that with the present technology, 78% of energy is

29

obtained through coal and natural gas while the remainder requirement is met with diesel,
gasoline and LP gas. The energy return ratio from ethanol when fossil fuel is used is as
low as about 1.6-1.7. However, the requirement of process heat alone is achieved by
utilizing 69% of DDGS. In this case, the energy returns realized are 2.9:]. Again by
consuming 76% of DDGS, process heat as well as electricity demands are met with this
the energy returns shift up to 4.7: 1. In case all the DDGS is utilized for energy needs, not
only process heat and electricity needs are met but also surplus electricity can be returned
to the grid and that energy return from corn ethanol becomes similar to that of
lignocellulose ethanol i.e. 5:1 [64]. Selling this electricity generates additional revenues.
However, the flip side of the story is that burning efficiency in a biomass burner is not
high, and DDGS is rich in proteins and lipids. Therefore, burning leads to the emission of
particulate matter and green house gases such as SOx , NOx and other volatile organic

compounds. Such compounds accrue to air pollution.

1.9.4 Mycotoxins

One of the important issues associated with the feed value of DDGS is mycotoxin
contamination. Mycotoxins are toxins produced by an organism from fungus kingdom,
which includes mushrooms, molds and yeasts [65]. They feed on organic matter, and
proliferate when humidity and temperature is sufficient. Mycotoxins are of various kinds
some are lethal, some cause diseases, some weaken the immune system, some act as
allergens or irritants, while some have no known effect on humans. Such toxins enter the
food chain due to fungal infection of crops. These toxins greatly resist decomposition in
digestion. They remain in the food chain in meat and dairy products. Even temperature

treatments such as cooking and freezing, are not enough to destroy many mycotoxins .

3O

Some of the important mycotoxins are Aflatoxins; they are produced by Aspergillus
species, mostly found in groundnuts, other edible nuts, figs, spices and maize. Aflatoxin
B1 is the most toxic one, it is a potent carcinogen and associated with liver cancer.
Mycotoxin such as Ochratoxin A, produced by Penicilliurn verrucosum, generally grows
in temperate climates. Aspergillus ochraceus, found as a contaminant in cereals and
related products, fruit, beverages and spices. It causes kidney damage in humans and is a
potential carcinogen. Patulin is a mycotoxin found in moldy fi'uits, vegetables, cereals
and other foods. It is destroyed by alcoholic fermentation. It may be carcinogenic and is
reported to damage the immune system and nervous systems in animals. Other
mycotoxins such as F usarium, Trichothecenes. Deoxynivalenol, and zearalenone are very
stable and can survive cooking. The trichothecenes are acutely toxic to humans, causing

sickness and diarrhea or even death [65].

Mycotoxins are a fungal infection that enters the corn kernels when the corn plant
is infected. Since these mycotoxins can survive fermentation process therefore they are
accumulated in every stage of processing. Mycotoxins concentration in DDGS are three
fold the initial concentration present in corn. In order to avoid the mycotoxins in DDGS
is to reject infected corn kernels. Swines and poultry are very sensitive to mycotoxin
contaminations. The issue of mycotoxin contamination is an important factor that limits

the scope of DDGS as feed to swine and poultry [66].

1.9.5 Carbon dioxide: a green alternative
Carbon dioxide is a colorless, odorless, non-flammable and slightly acidic gas in

nature. Carbon dioxide is produced by different processes in combustion or fermentation

31

of organic matter. Our source of consideration is corn starch fermentation. Today about
18 lb of carbon dioxide is produced by fermentation of a bushel of corn. In the year 2006,
1.8 billion bushels of corn were dedicated for ethanol production [25]. Such amount of
corn when fermented produced about 32.4 billion lbs C02. This amount of carbon
dioxide is cumulative of dry milling and wet milling of corn. Carbon dioxide finds
numerous applications in food industry that include its use as a green chemical used for
solvent extraction techniques, carbonating agent in beverage industry, water treatment.
Carbon dioxide gets dissolved in water to form carbonic acid. This finds water treatment
application in reducing and controlling the pH of water. Conventionally sulfuric acid is
used for water neutralization purposes. However sulfuric acid has lots of environmental
considerations and operational hazards associated with it. There are many advantages of
carbon dioxide over mineral acids. Carbon dioxide has no carcinogenic effects on
humans, while the sulfuric acid mist has carcinogenic effects and that stringent control
are required to maintain permissible exposure limits below 1mg/m3 [67]. Unlike mineral
acids, CO2 is safer and cheaper. Typically sulfuric acid has a trade value of $ 55 to $ 65
per ton and in contrast C02 is sold approximately 8 4 per ton [68]. Regarding water
treatment, C02 has improved controllability over mineral acids. The mineral acids, in
particular sulfuric acid initially shows a little change in pH till a certain point followed by
a steep decline in the pH values which makes it difficult to control the neutralization end
point [69]. Performance suggests that depending upon the nature of impurity, a lesser
amount of carbon dioxide is required for neutralization. Also the unit price differences
justifies the overall cost effectiveness for the use of C02 in water treatment. Another

aspect is the raw material handling and storage. As regards to the piping system, to

32

handle the chemicals, there is lots of maintenance associated with the pipes carrying
sulfuric acids. Mineral acid tends to corrode the internal surface of pipelines [70]. In case
of carbon dioxide, the carbonic acid is in situ produced when it comes in the contact of
water. The dry carbon dioxide gas itself is harmless in nature thus the pipelines that carry
C02 have little associated maintenance. The continuous water treatment demands to have
a bulk onsite storage of mineral acids and the equipment costs and maintenance of the
storage system is very high. In contrast, there is no need for bulk storage of carbon
dioxide as there is a convenient option of pipeline transportation for continuous supply.
An important application of carbon dioxide is to prepare precipitated calcium carbonate
(PCC). Rectangular flakes of PCC having average diameter and thickness of about 1.75
micrometer and 0.2 micrometer respectively. C02 gas fed at a rate of 200 ml/ min into the
suspension containing 0.10% (m/v) of Ca(0H)2 at 25 °C [71, 72]. Industrial use of this
compound is as filler in the process of paper making. PCC is known to enhance the
optical properties and print characteristics of paper and related products. It makes paper
more machine able. PCC is added as a filler in the paper this helps reducing more
expensive pulp fiber while papermaking. This filler is low cost filler thus contributes to
the capital savings and helps conserving precious wood. For the premium brand of paper
it serves as an optical brightening agent. PCC is used in plastic industry as filler. Nano
PCC acts as a viscosity modifier and sag reducer in automotive parts and construction
sealants. PCC as a filler in the polymer matrix improves the elastic modulus and at the
same time synergistically improves the low temperature impact strength. Therefore PCC
is an alternative to expensive organic impact modifiers. In the paint formulations, due to

its optical properties, it replaces costly titanium dioxide and improves opacity. For health

33

care applications, PCC is used as an acid neutralizer, typically as a calcium-based antacid
tablets and liquids. PCC is rich in calcium content that allow a drug formulation having
high dosage of calcium supplements in mineral tablets. Controlled small particle sizes
and unique particle shapes of PCC finds application in good tasting calcium fortified
foods and beverages. Carbon dioxide finds applications such as in making dry ice,

refrigerant, textile dying, fire extinguisher [73-75].

1.10 Resource utilization of corn plant

A sustainable approach demand maximum resource utilization. A laboratory scale
experiment was conducted in order to assess what fraction of the corn plant by weight
(dry basis) gets converted into ethanol. Experiment deals with selection of a genetically
modified variety of corn Bacillus Thuringiensis (BT). Corn plants were procured from
3660 meridian farm (courtesy Bruce Noel). Gathered plants were fully matured and ready
to harvest. Procured plants were then oven dried at 110 °C for 8 hours until the dry
weight was constant. Dry weight measurement was done for 26 com plants. Weight of
various parts were measured separately and correlated for weight fiaction of carbohydrate
source that is utilized for ethanol conversion. Weight distribution of various parts of corn
plant are shown in Table 3 and Table 4 [76]. On dry weight basis, assume the total corn
plant to weight 100 lbs. Based on the experimental findings, the weight of the car would
be 63 lbs of which 52 lbs (0.928 bu) accounts for the weight of kernels. Present rate of
fermentation of corn sugars into ethanol accounts for a conversion of 2.8gal/bu [34].
Therefore, the amount of ethanol produced per 100 lbs (dry basis) of corn plant equals
2.6 gal (0.928Bu* 2.8gal/bu) which is equivalent to 17 lb of ethanol. Material balance

suggests that, a 100 lb corn plant has a productive output of 17 lb of ethanol this

34

corresponds to 1/6th of total corn plant by weight. Amount of DDGS that is formed is
16lbs and about 16lbs of carbon dioxide is produced. Remaining 48 lbs which

corresponding to stalk, roots and leaves is referred to as corn fodder.

Table 3: Corn plant weight distribution on dry basis (after ref 76)

 

 

 

 

 

 

 

Corn plant components Average Value SD
Stalk weight (g) 50 16
Leaves weight (g) 33 10
Ear weight (g) 183 40
Roots (g) 24 12

Total Dry Weight (g) 290 71
Total height (inch) 85 10

 

 

 

 

 

Table 4: Ear weight distribution on dry basis (after ref 76)

 

 

 

 

Ear Weight Distribution Average Weight (g) SD
Kernels 152 34

Cob 23 6

Ear leaves 1 l 4

 

 

 

 

 

1.11 Economic impact

Economy is an integral aspect of sustainability. Stringent environmental
conditions, choice of raw materials, advanced technologies and infrastructure leave little

room for the situation to be cost effective. Now on the other side, consider the pathways

35

that rely on petroleum based raw materials and fossil fuels, although convenient but they
leave no room for things to be lasting for the generations to come. Sustainable growth
and development is definitely expensive, but this is not an economic stalemate. A
sustainable system in the initial phase is expensive however, in the long term it pays back
with better future in terms of material security, quality environment and health. Economy
is the most important driving force that defines the scope of industrialization, exploitation
of resources, demography and their related issues. Any geographical terrain has its
limited resources and ecological tolerance. Now consider a situation that in a given
city/region there is a industrial setup due to such an infi‘astructure there is forced human
population density and resource utilization. Economical growth leads to expansion in
infiastructure, transportation and production therefore more people will be drawn to
reside in that region. Now with increasing non sustainable economic activity the
ecosystem gets more and more stressed. Resource per capita depletes, and environmental
conditions deteriorate and so do the human health and environment in spite of their
tolerance limits. Environmental conditions worsen once there is accumulation of
pollution in the ecosystem. Consider the concept of micro ecosystem where economy is
local and so will be the associated environmental burdens. Burning example is the corn
ethanol industry with an ever-increasing demand of sustainable green fuel; it has led to
the exponential growth of ethanol distilleries. This is a situation of an economic boom
where the industrial grth is concentrated around the com-belt regions due to factors
like ease of transportation and low prices of corn. Corn dry milling generates enough
DDGS as coproducts whose production will exceed consumption in the immediate future.

Absence of sustainable pathways to handle the surplus of DDGS makes it a potential

36

environmental hazard. Therefore, the growth of any industry should be done a sustainable
manner. Another important aspect is energy efficiency and material reutilization. A
sustainable system has well defined boundaries beyond which the criterion is not met
with. The concept of sustainability that holds true for micro ecology holds true for global
ecosystem at large. Analogy is extended when we consider earth as ecosystem and
analyze effects of growing economy on the global population growth and global
atmosphere.

Nevertheless in contrast to fossil fuels, corn based ethanol is green and it is has
contributed substantially to the US economy. In the year 2006, the ethanol industry
including operations, fire] transportation and infrastructure development, has lead to an
increased gross output of $41.1 billion. The ethanol industry generated 160,231 job
opportunities in almost all economic sectors of which ~ 20,000 jobs in the manufacturing
sector alone [25]. These job opportunities contributed to a house income of $6.7 billion.
The ethanol industry contributed to tax revenues worth $2.7 billion to the federal
government and $2.3 billion for the state respectively [25]. The consequence of such an
economic impact is socio-economic growth and the tax revenues can be utilized for the
benefit of society. Thus corn ethanol is utilizing renewable resources to make green fuel,
and in turn provides opportunity for employment and prospering society. Corn ethanol is
a good example of a potentially sustainable economy. Table 5 suggests the prospects of
the grth of corn ethanol industry [77]. As per the projections, it looks that the
expansion of ethanol plants is exponential till 2007 after that there is drastic decline in the

growth rate of ethanol infrastructure [77]. By 2015 the contribution of corn to make bio

37

ethanol is likely to decrease a little bit due to the use of other grain feed stocks and lingo-

cellulose ethanol inputs.

Table 5: Prospects of the growth of corn ethanol industry (after ref 7 7)

 

 

 

 

 

 

 

 

 

 

 

 

 

Year Ethanol Net New Corn Ethanol Yield
Production Capacity Share (gal/Bu)
(MGY‘) (MGY) M)

2005 4003 686 90 2.75
2006 5615 1625 90 2.765
2007 7230 1700 90 2.78
2008 7943 750 90 2.795
2009 8323 400 90 2.81
2010 8703 400 89 2.825
2011 8988 300 88.5 2.84
2012 9225 250 88 2.855
72013 9463 250 87.5 2.87
2014 9653 200 87 2.885
2015 9843 200 86.5 2.9

 

 

 

 

 

a: MGY= Million gallons per year

38

 

Table 6 compares the benefits realized by a corn ethanol plant of 50 million gallons and
100 million gallons capacity [77].

Table 6: Economic implications of ethanol facilities (after ref 7 7)

 

 

 

 

 

Parameters 50 MGY 100 MGY
Annual Expenditures (Million 20053 a) $46.7 $88.2
Gross Output (Million 2005$) $209.2 $406.2
Household income(Million 2005$) $29.7 $51.2
Employment (jobs) 836 1573

 

 

 

 

 

’ mm = Value of the us dollar in the year 2005

Ever growing bioethanol production has influenced the price of corn. Evaluating
the implications of corn ethanol on the food prices, some consider that the bioethanol is
responsible for the food prices hike [78]. While others believe that, the rising crude oil
price is responsible for food price hike. These viewpoints are compared using Consumer
Price Index (CPI), which is an important tool to study inflation. CPI is the ratio of the
cost of specific consumer items in any one year to the cost of those items in the base
period. In the US, CPI for food had accelerated in the recent past. Apparently, it seems
that the increase in the CPI for food is solely due to the high prices for corn influenced by
increasing ethanol production. However, hike of the corn price is only one of many other
contributing factors that control the CPI. In fact, there is little direct influence of corn
price on retail food prices. In contrast, the rise in the prices of fuel and energy has a lot
greater impact on not only to the food prices but also on any other material in market; as
every thing requires energy for manufacturing. In order to estimate economic influence, it
is important to compare the effect of the fuel price hike to that of the corn price hike.

Consider a $1.00 per gallon increase in the price of gasoline, doing so increases the CPI

39

for food by 0.6 percent to 0.9 percent. While an equivalent increase in corn prices ($1.00
per bushel) would cause the CPI for food to increase only 0.3 percent [78]. Corn prices
have half the influence on CPI than does the fuel price hike. Table 7 shows the price of a
variety of food stuff. Prices of commodity are compared for year 2006 and 2007 [79, 80].
On the basis of selected food stuff, which is the leading components of US grocery, the
average increase in the price for these food items is about 3% and that average annual
food inflation over 25-year is 2.9%. Thus, there is not a significant impact on the inflation
of food prices due to corn price hike. In the US, corn is the most valuable agriculture
produce. Crop value of corn in the year 2006 was 33.71 billion dollars followed by
soybean, which ranks second most valuable crop having half the worth of com [52].
Figure 11 shows the relative worth of major crops produces in the US [52]. Continuation
to the discussion of corn prices, Fig 12 shows the price trend for past 50 years [52]. In
2006, there is a jump in the price of corn of about $1/Bu. This is indicative of rising local
economy. Prior to this, the corn prices fluctuated around $2/ bu when averaged for almost
a decade. The US is a leader in the corn exports. In the Figure13, US alone contribute to
the worlds 69% of the corn exports followed by Argentina (5%of worlds export) and
China (55 of world exports). The US exported about 2250 million Bu in the year 2006
[52]. Historic trend of the US corn exports is shown in the Figure 14 [52]. The impact of
corn ethanol has not affected the international trade of corn. In the year 2006 the US
became the largest producer of bioethanol and this year it had an all time high in corn
export yet the sensitive balance of international trade maintained. Bioethanol and DDGS

are generated in proportional quantum ratio; the growth trend of DDGS follows a similar

40

exponential trend. Figure 15 shows the production in millions of ton of DDGS for last 8

years [25].

Crop Value (billion 3)

Corn Price (SIBu)

401

30*

207

104

0.17 0-52

 

 

0 EL..._.——__ ___7— r

 

Oats Barley Sorghum Wheat Soyabean Corn

Figure 11: US Crop value for different crops (after ref 52)

 

 

 

 

4

3,-

2.

1* 1.24 1'5

Owwe—r—wlrrwlfrryrerl
56 66 76 86 96 97 98 99 00 01 02 03 04 05 06

Year

Figure 12: Historic prices of corn in the US (after ref 52)

41

Table 7: Comparative prices of food for year 2006 and 2007, (after ref 79,80)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Commodity Qty Price (April 06) Price (April 07)
Milk 1 gal. $3.12 $3.14
American Cheese 1 lb. $3.81 $3.73
Butter '/2 lb. $1 .40 $1.43
Ice cream 1/2 gal. $3.62 $3.79
Turkey 2 lbs. $2.22 $2.16
Chicken breast 2 lbs. $6.62 $6.74
Eggs 1 dz. $1.28 $1.62
Pork Chops 2 lbs. $6.34 $6.30
Bacon 2 lbs. $6.68 $7.00
Ground beef 1 lbs. $2.74 $2.82
Beef steak 2 lbs. $10.18 $10.82
Cola, non-diet 2 ltrs. $1.10 $1.20
Malt Beverage 72 023. $5.00 $5.00
TOTAL $54.11 $55.75

 

 

 

 

 

42

 

«Nu. RY 6&5 «.593 53 2.5.; E Esra—owne— mb 2:. "2 PEME

         

$3 «nu-BME

.xem .mnwum

sew e55

e\e$ <mD
e\eN 22:0

e\e_ mint—D
e\e~ «Baum

.XL «Ea—norm e\e~ nor—.3. 55w
.x; .53?an

Exports (Million Bu)

2500 1
2147 2250

1979
2000 . 1794 19371941 1905 19001818

1 584 1 503 1 588
1500 1
1000 I
I
500 I
I

91 96 97 98 99 00 01 02 03 04 05 06

Year
Figure 14: Historic trend of the US corn export (after ref 52)

9.0
7.3
8 I

1999 2000 2001 2002 2003 2004 2005 2006

—L

12.0

A A
a, a O N -h
1 I 1 r 4

h
r

 

DDGS production (million tons)

   

Figure 15: Recent trend of DDGS production (after ref 25)

Chapter - Bioadhesives

1.12 Introduction
Most of the adhesives those are currently used are from petroleum sources.

Therefore, there is an urge to produce adhesives from renewable resources [81].
Nowadays there are a lot of research is going on producing natural adhesives
(bioadhesives) for the environmental concern. Starch based and protein based adhesives
are the major bioadhesives. A variety of chemical treatment is necessary in extracting or
formulating bioadhesives from the starch or protein source.

For wood products, the commercially used adhesives are synthetic one and due to
environmental reasons, the non-toxic adhesives are required. Non-toxic starch based
adhesives have been reported for application in wood products [82]. High strength straw
particleboards can be produced when bonded with soy proteins modified with urea, citric
acid, boric acid and sodium hydroxide [83]. NaOH-modified SPI increased the tensile
strength and compression strength of the particleboard from wheat straw and corn stalk
pith [84]. Guanidine hydrochloride (GuHCl) denatured soy protein isolate resulted in an
unfolded and loose protein conformation, which helped in improved the shear strength of
SPI adhesive to fiberboard [85]. Modification of rice barn using heat and alkali improved
its adhesive strength over the unmodified bran to bind plywood, particleboards, and
fiberboards [86]. Many treatments have been done to make adhesives from starch based
material. Another approach is to make starch based adhesives that go for corrugated
cardboard applications. Here the corn starch has been treated with sodium hydroxide
(NaOH) along with other salts. This adhesive provides good bond strength for application
in corrugated cardboard manufacture [87]. Another use is in paper packaging where

starch based adhesives can be used. Here the flour have been treated with different

45

compounds resulting in adhesive which has high adhesion, fast drying time and stable
storage [88]. Adhesives for corrugated board were prepared by alkali treatment of corn
starch [89]. Carbohydrate adhesives derived from yam corn, potato and cassava starch
when modified by acid moisturing and roasting resulted in high tack having adequate
bonding strength for paper—paper and paper—glass substrates [90]. Environment friendly
adhesive was prepared by crosslinking starch and PVOH for wood binding applications,
adding latex in the formulation showed further increase in the adhesion [91] .

Soy protein based adhesives has shown great adhesion properties to cellulosics
and other materials for the production of particleboard, plywood, and various composites
[92]. The main weakness of a protein-based adhesive lies in its relatively poor water
resistance for outdoor uses. Various chemical and enzymatic methods have been tried to
improve the adhesion of soy protein. Research has been done to study the effects of
esterification of soy protein on adhesive strength. Free-carboxyl groups of soy protein
are esterified with ethanol along with different concentrations of hydrochloric acid as
catalysts. Moderate esterification resulted in better adhesion strength and better water
resistance. With the optimum esterification the wet strength increased around 62 % [93].
Another approach also has been taken in improving wet strength of the soy adhesives.
Different chemical modifications have been done to increase the wet strength of the soy
bean based adhesive [94]. Increasing mercapto functionality significantly improves the
wood adhesion for soy proteins. The adhesion strength and water-resistance of the wood
adhesive increases as —SH groups increase in the soy protein [95]. Polyurethane (PU)
adhesives that were synthesized fiom potato starch and natural oils by a

transesterification reaction resulted in adhesive which was superior than commercial

46

counterparts [96]. Soy protein when blended with polycaprolactone using coconut oil as
compatibilizer improves strength and cost effectiveness [97]. Most of the adhesives that
are used mostly comprised of formaldehyde resin like urea-formaldehyde or phenol-
formaldehyde. Formaldehyde is carcinogenic [98]. Therefore it is much important to
prepare formaldehyde-free adhesives from soy protein [99, 100]. In this process
formaldehyde — free curing agent like amine, amide, etc. have been tried to make
bioadhesive more coo-friendly. These adhesives can be used for application on
lignocellulosic materials as well as in composite manufacture. For the fiberboard
production, that is widely used for packaging materials, containers, tubes, and cartons,
these soy protein based adhesives resulted in better dry, wet strengths [81]. Therefore,
from the sustainability and environmental point of view there is the need for producing
bioadhesives from DDGS, which will help in supporting the economy of the com-ethanol

industry.

1.13 Materials and methods

Sodium hydroxide (N aOH) and potassium hydroxide (KOH) were obtained from
Columbus Chemical Industries, Inc. (Columbus, WI). Urea was obtained from Spectrum
Quality Products, Inc. (Gardena, CA). Distillers’ dried grains with solubles (received
DDGS contains 9% moisture) were obtained from Michigan Ethanol (Caro, MI). The
bioadhesive compositions were prepared from as received DDGS. The protein content of
the DDGS was measured to be 27% using a Perkin-Elmer elemental analysis instrument
(CI-IN 2400, Series II CHNS/O). Protein Glue (Ground Hide Glue, Item #TAD032001)
and precooked wheat starch (Wheat Paste No. 301 , Item #TAD002001) were obtained

from Talas, New York. Paperboard: Custum Kote® from Mead Westvaco, the thickness

47

of paperboard was 18 mils, having white coating on one side for printing purposes while
the other side was brown were used in our experiments to study the adhesive strength.
Pressure cooker used for the cooking was MAXI-MATIC® EC-8, Maxi-matic

Appliances Industry, CA.

0

NH2 0 NH2

Figure 16: Chemical Structure of Urea

 

1.14 Preparation of bioadhesive from DDGS

1.14.1 Variation in reagent concentration NaOH and Urea

For the synthesis of bioadhesives, key destructurizing reagents i.e NaOH and urea
shown in Figure 16, were dissolved in distilled water to prepare a NaOH-urea solution.
140 mL of the NaOH-urea solution containing NaOH (1.4g to 5.6 g), Urea (0 to 4.2 g)
and water (131.6 g), were mixed with 30 g of DDGS. The resulting slurry was cooked in
a pressure cooker for 15 minutes. The cooking pressure as calculated was 1.6
atmospheres (refer section 3.4.3). The cooked slurry was then diluted with 50 g of water
followed by filtration under vacuum using Buckner funnel that is mounted over an
Erlenmeyer flask. In this filtration process, a polyester-cotton cloth was used as the
filtering medium. After filtration, the solids were retained over the cloth while suspension

was collected in an Erlenmeyer flask. The solids collected over the filter cloth were

48

washed again with distilled water (about 200 g) for 10 min and filtered again. The
washed solids were collected and dried at 110 °C. The suspension was concentrated into a
three-necked flask and concentrated at 100 °C for about 4 hours to evaporate most part of
water. The concentrated suspension resulted in a brown and viscous fluid; considered as

the bioadhesive from DDGS [101].

1.14.2 Effect of pressure

In order to determine the effect of pressure as a processing variable, 140 mL of
the NaOH-urea solution containing NaOH (4.2 g), Urea (4.2 g) and water (131.6 g), were
mixed with 30 g of DDGS. The slurry was cooked at ambient atmosphere (1.0 atrn) for
15 minutes. The cooked slurry was diluted using about 50 g of water followed by
filtration under vacuum using Buckner funnel that is mounted over an Erlenmeyer flask.
In this filtration process, a polyester-cotton cloth was used as the filtering medium. After
filtration, the solids retained over the cloth while suspension was collected in the
Erlenmeyer flask. The solids were washed with distilled water (about 200 g) for 10 min
and filtered again. The washed solids were collected and dried at 110 °C. The
suspension was charged into a three-necked flask and concentrated at 100 °C for about 4
hours to evaporate most part of water. The concentrated suspension was a brown and

viscous fluid is referred to as the bioadhesive from DDGS.

1.14.3 Effect of cooking time
In order to study the cooking time as processing variable, 140 mL of the NaOH-
urea solution containing NaOH (4.2 g), Urea (4.2 g) and water (131.6 g). were mixed

with 30 g of DDGS. The slurry was cooked in a pressure cooker for 25 minutes and 35

49

min. The cooking pressure was 1.6 atmospheres. The cooked slurry was diluted using
about 50 g of water followed by filtration under vacuum using Buckner funnel that is
mounted over an Erlenmeyer flask. In this filtration process, a polyester-cotton cloth was
used as the filtering medium. After filtration, the solid residues were retained over the
cloth while suspension was collected in the Erlenmeyer flask. The residues were washed
with distilled water (about 200 g) for 10 rrrin and filtered again. The washed residues
were collected and dried at 110 °C. The suspension was charged into a three-necked flask
and concentrated at 100 °C for about 4 hours to evaporate most part of the water. The
concentrated suspension was a brown and viscous fluid; considered to as the bioadhesive

from DDGS.

1.14.4 Effect of filtration

Two sets of adhesive batches were prepared. In one of the formulations, NaOH was
dissolved in distilled water to prepare a NaOH solution. 140 mL of the NaOH solution
containing NaOH (4.2 g) and water (135.8 g) were mixed with 30 g of DDGS to form
slurry. In another formulation, 140 mL of the NaOH-urea solution containing NaOH (4.2
g) and urea (4.2 g) and water (131.6 g), were mixed with 30 g of DDGS to form slurry.
In both the formulations, the slurry was cooked at ambient atmosphere (1.0 atrn) for 15
minutes. The cooked slurry was collected in a polyester-cotton cloth and squeezed by
hands thereby separating solid residues (retained in the filter cloth) from aqueous
suspension. The residues were washed by use of distilled water (about 200 g) for 10 min.
and squeezed again. The residue was finally collected and dried at 110 °C to obtain dried

residues. The suspension was concentrated in a three-necked flask and concentrated at

50

100 °C for about 4 h to evaporate most part of the water. The concentrated suspension

was a brown and viscous fluid, which was considered as the bioadhesive fiom DDGS.

1.15 Characterizations

1.15.1 Yield of DDGS bioadhesive
The yield of the bioadhesive composition was based on the amount of DDGS
that was converted into bioadhesive systems. The yield is calculated by using the

following equation:

Yield of bioadhesive (%) = 100 — (Weight of dried residues/initial weight of the as

received DDGS taken) x 100.

1.15.2 Moisture content measurement
Weighed sample (W1) was dried in an oven at 110°C. Eight hours later, the dried
sample was taken out and weighed (W2). Water content of the sample is calculated using

the following equation

Moisture (%) = [(Wl - W2)/W1] x 100

1.15.3 Cooking pressure measurement
Pressure cooker operates at a constant pressure which is maintained by periodic
discharge of steam through a nozzle over which a weight rests. The cooking pressure is

calculated by using the following equation

Cooking pressure (atrn) = weight over the nozzle/the area of the nozzle cross section.

51

1.15.4 Lapshear strength

Lapshear samples were prepared from paperboard that was cut into rectangular;
two such strips were bonded with bioadhesive having 50% of solid content. Bioadhesive
was applied to only one of the paperboard strips having a spread area of 1 square inch
containing 0.053 g of adhesive on wet basis. The adhesive was applied to bind the non-
coated sides of the paper board. Bonded paperboard samples as shown in Figure 17 ,
were pressed and cured for around 9 hours time at ambient conditions. The bonded
paperboards were subjected for lapshear strength testing. Failure of lap joint during
testing of lap shear specimens is shown in Figure 18. The testing details were provided in
standard of TAPPI T813 for paper samples. Samples were tested at a cross head speed of
0.5 inch per min. In regard to the curing of paperboard specimens for lapshear testing,
the prepared samples were placed between two thin metal sheets with dimensions 10” x
10”. Pressure was applied to the specimens by placing a rectangular iron slab weighing
22 lbs over the lap joints which were sandwiched between metal sheets. Set up for curing
is shown in Figure 19. Under these conditions, samples were allowed to dry for about 9
hrs. Curing conditions for the samples prepared using commercial starch and protein
adhesives were kept the same as that of other bioadhesives made from DDGS. Then the
lap shear strength was measured. Solid content in the bioadhesive compositions were
maintained as 50% and the method is explained as follows: The bioadhesive formulation
was concentrated until the solids content of the adhesive was greater than 50%. The water
content of the bioadhesive was measured. Then the adhesive was weighed and added with
distilled water to adjust the total water content to be 50%. The 50% starch slurry has no

spread ability thus for convenience a 25 wt% starch slurry was prepared. In order to keep

52

amount of solid content consistent with bioadhesive, the wet amount of starch adhesive

was doubled over the lap area.

53

 

Figure 17: Test specimen for lap shear strength

(a)

 

Figure 18: Post lap shear testing mode of failure.
(a): Lap joint

54

 

Figure 19: The setup for curing; (:1): Iron bar weighing 22 lbs placed over iron sheet
for uniform distribution of load, (b): Paperboard samples, (c): Lap joint, (11): Iron
sheet placed at top and bottom of samples

1.15.5 Viscosity measurements

Brookfield viscosities of bioadhesive compositions with various solid contents
were measured using a Brookfield digital viscometer (Model DV-II, Brookfield
Engineering Laboratories Inc. (Stoughton, Massachusetts) with a thermal cell attachment.
Spindle number is 21. Sample (8 - 13 mL) was poured into a vessel at a given
temperature. After the samples were equilibrated in the thermal cell for 10 nrin, the motor

of the viscometer was turned on to record Brookfield viscosity at a given speed.

1.15.6 Infrared spectroscopy
The infrared spectrum was obtained using a FTIR spectrophotometer (Spectrum

2000, Perkin Elmer, MA). The spectrophotometer had an attached ATR facility.

55

Spectrum of DDGS, residual fibers and dried bioadhesives were taken in order to observe
the chemical structural modifications. The samples were analysed in the wavenurnber

range of 4000- 650 cm'l.

1.15.7 Elemental analysis

In order to determine the protein content of DDGS, an elemental analysis was
carried out where carbon (C), Nitrogen (N) and Hydrogen (H) contents were estimated.
For each samples three runs were carried out to obtain the average elemental
composition. For CHN elemental analysis the samples were oven dried over night at 100

°C. The samples were then made powder using a mortar and pestle prior to testing.

1.15.8 Thermal gravimetric analyzer

The thermal behavior characteristics were evaluated using thermal gravimetric
analyzer 2950 series from TA Instruments(TA Wilmington, DE). The mass loss
measurements were conducted in a nitrogen atmosphere. Using an auto sampler, the
samples were mounted on the TGA balance. Temperature was equilibrated before each
sample run. The nitrogen gas flow rates were maintained at 70 cc/min. The samples were

exposed to a temperature ramp of 20 °C/ min.

56

Chapter - Results and Discussions

1.16 Synthesis of bioadhesive
Bioadhesive was prepared from DDGS in the presence of aqueous alkaline media
and boiling temperature. The variables used in the making bioadhesives are alkali

concentrations, residence time and cooking pressure.

1.17 Variation in reagent concentration NaOH

Various bioadhesive formulation were prepared in which the alkali (NaOH)
concentration was varied from 0 to 5.6 g/30g DDGS. Samples in which the alkali
concentration was varied had urea content constant i.e. 4.2 g/ 30g DDGS and keeping the
cooking time 15 min and cooking pressure of 1.6 atmospheres. Sample in which urea
alone was present, after cooking, showed no tack initially inspected by hand feel and
preliminary test on paperboard adhesion. In the samples where the alkali concentration
was increased in the multiples of 1.4g , it was observed that with increase in alkali
concentration there was increase in the bioadhesive yield while the lapshear strength had
fluctuating yet increasing trend. For the highest alkali concentration the bioadhesive
conversion yield was maximum however, the lapshear strength decreased in the case of
paperboard samples. Lapshear strength dependence on the alkali concentration is shown
in the Figure 20. In case of wooden samples the trend of lapshear strength was
monotonously increasing as shown in the Figure 21. The effect of alkali reagent
concentration on bioadhesive yield is shown in the Figure 22. The plotted data is shown

in the Table 8 and Table 9.

57

160 I 135
f: 127

120 1 93

       

77"— I if I fi—

1.4 (1 N3U) 2.3 (2N3U) 4.2 (3N3U) 5.6 (4N3U)
Alkali concentration (gl309 DDGS)

Figure 20: Lapshear strength dependence on the alkali concentration for
paperboard samples

Lapshear Stren

220 1
171
170 ~

120 -

70-

 

I — ”—7

1.4(1N3U) ‘ 2.8(2N3U) 4.2(3N3U) 5.6(4N3U)
Alkali Concentration (gl309 DDGS)

Figure 21: Lapshear strength dependence on the alkali concentration for hard
maple wood samples

 

Lapshear Strength (psi)

 

 

11:10.

1.4 (1 N3U)

2.8 (2N3U) 4.2 (3N3U) 5.6 (4N3U)

Alkali Concentration (gI30g DDGS)
Figure 22: Effect of alkali concentration on the yield of bioadhesive

 

4.2 (3N)

Table 8: Lapshear strength of difl'erent bioadhesive for paperboard samples

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Sample DDGS NaOH Urea Cooking Cooking yield (%) Lapshear
code (g) (g) (g) time pressure strength
(min) (atrn) (psi)
3U 30.0 0 4.2 15 1.6 - -
1N3U 30.0 1.4 4.2 15 1.6 13 :l: 1.55 93 :l: 11
2N3U 30.0 2.8 4.2 15 1.6 57 :l: 1.52 135 :l: 7
3N3U 30.0 4.2 4.2 15 1.6 67 i 0.77 127 i 7
4N3U 30.0 5.6 4.2 15 1.6 70° :l: 0.78 113 i 2

 

59

 

Table 9: Lapshear strength of different bioadhesive for hard maple wood samples

 

 

 

 

 

 

Sample DDGS NaOH Urea Cooking Cooking yield Lapshear
code (g) (g) (g) time pressure (%) strength
(min) (atm) (psi)
3U 30.0 0 4.2 15 1.6 - -
1N3U 30.0 1.4 4.2 15 1.6 13 $1.55 60 :l: 15
2N3U 30.0 2.8 4.2 15 1.6 57 :l:1.52 135 i 22
3N3U 30.0 4.2 4.2 15 1.6 67 :l:0.77 158 i 19
4N3U 30.0 5.6 4.2 15 1.6 70°: .78 171 i 46

 

 

 

 

 

 

 

 

 

 

From the above results it can be inferred that the principal de-structurizing agent
is alkali and that urea has negligible role. Urea upon cooking, was degraded as indicated
through a pungent ammonia smell. Attempts were made to increase the yield of
bioadhesive by using alternate bases. Alternatives such as calcium carbonate, guanidine
hydrochloride, sodium sulfite were used in place of sodium hydroxide. Most promising
results came from potassium hydroxide however the bioadhesive yield and lapshear
strength were both compromised. The effects of sodium hydroxide and potassium

hydroxide in bioadhesive formulation vs performance are shown in Table 10.

60

Table 10: Effect of alone sodium hydroxide and potassium hydroxide on bioadhesive

yield and lapshear strength for paperboard samples

 

 

 

Received NaOH KOH Urea Cooking Cooking Bioadhesive Lapshear
DDGS (g) (g) (g) time pressure yield (%) strength
(2) (min) (atm) (Psi)
30 0 4.2 0.0 15 1.6 53 109 :I: 6
30 4.2 0 0.0 15 1.6 67 123 i 7

 

 

 

 

 

 

 

 

 

 

1.17.1 Curing time characteristics of adhesive

The lapshear samples were optimized for the curing time and temperature. The
optimization is based on the lapshear strength form the samples of paperboard. It was
observed that for paper board the optimal curing time at room temperature was 9 hours.
However at elevated temperature of 80 °C the optimal time was 4 hours. The rational
behind the high temperature curing is lesser adhesive curing times. The curing
temperature of 80 °C was chosen because at still higher temperatures there were bubble
formations due to high evaporation rates of water vapor originating from wet adhesives.
The data for curing time optimization is shown in Table 11

Table 11: Curing time optimization

 

 

 

 

Temperature(°C) Time (hours)
2 4 6 9 12
23 0C - - 119i13 127:1:7 130:4
80°C 104i9 116i5 115:1:4 - -

 

 

 

 

 

 

 

 

61

1.17.2 Effect of pressure

The bioadhesives were prepared by varying cooking pressure keeping residence

time , reagent concentration and other processing variables constant . In a pressure cooker

the amount of pressure developed was 1.6 atmospheres.

Two reagent systems were

compared one having the urea and the other one without urea. The atmospheric cooking,

in both cases, showed a slight increase in the lapshear strength values than compared with

those adhesive formulations prepared at 1.6 atmosphere cooking pressure. The increase in

the lapshear strength is not significant therefore it can be concluded that there was

practically no significant effect of pressure on the yield and lapshear strength of DDGS

based bioadhesives. Lapshear strength and conversion yield data are shown in the

Table] 2.

Table 12: Effect of pressure on the bioadhesive yield and lapshear strength for
paperboard samples

 

 

 

 

 

 

 

 

 

 

 

 

 

Sample Received NaOH Urea Cooking Cooking yield (%) Lapshear
code DDGS (g) (g) time pressure strength
(3) (min) (atm) (Psi)
3N3Umm 30.0 4.2 4.2 15 l 67 i 1.6 129 i 3
3N3U 30.0 4.2 4.2 15 1.6 67 i 0.77 127 i 7
3Natm 30.0 4.2 - 15 1 67 d: 0.8 129 i 7
3N 30.0 4.2 - 15 1.6 67 i: 0.28 123 i 7

 

62

 

1.17.3 Effect of residence time

Another process variable is the residence time while cooking. The cooking time
was varied fiom 15 min to 35 min in the interval of 10°C. The objectivity was to find
effect of residence time on the yield of bioadhesive. It was observed that there was no
significant increase in the yield. The data for the yield against the residence time is shown

in the Table 13.

Table 13: Effect of residence time on the bioadhesive yield and lapshear strength
for paperboard samples

 

 

 

 

Sample Received NaOH Urea Cooking Cooking Bioadhesive Std

Code DDGS (g) (g) time pressure yield (%) Dev
(3) (min) (atm)

3N3U 30.0 4.2 4.2 15 1.6 67 0.77

3N3U‘ 30.0 4.2 4.2 25 1.6 68 0.35

3N3U‘ ‘ 30.0 4.2 4.2 35 1.6 69 0.87

 

 

 

 

 

 

 

 

 

 

1.17.4 Effect of filtration

All the bioadhesive samples prepared from DDGS unless specified were filtered
under vacuum using Buckner funnel mounted over an Erlenmeyer flask. In this filtration
process, a polyester-cotton cloth was used as the filtering medium. The yield of bio
adhesive is drastically affected by the method of filtration. Two filtration methodologies
were compared in term of the yield of bioadhesive. The polyester-cotton filter cloth in
both the cases was kept constant. Other filtration method adopted for comparison is

squeeze filtration. In this method, the cooked slurry was collected in a polyester-cotton

63

cloth and squeezed by hands thereby separating solid residues (retained in the filter cloth)
from aqueous suspension. The residues were washed by use of distilled water for 10
minutes and squeezed again. In vacuum filtration it was observed that solids near filter
cloth formed cake and hampered the flow of bioadhesive. The time required in this
method was about 2 hrs. In contrast the squeeze filtration is very fast process however the
yield of bioadhesive is a function of applied force. This method by hand has variable
results. Moreover when the slurry is squeezed the pore size of the filter gets expanded.
This allows ultra fine fibers to pass through. The effect of filtration on the lapshear
strength is shown in the table 14. As a control experiment a bioadhesive sample was
prepared which was not filtered but instead after cooking the slurry was blended in a
mixer for 5-10 minutes. It was observed that the ultrafine cellulose fibers present in
DDGS even after alkaline treatment really does not impart to the tack. In the Table 14 it
is evident that as the fiber content increases in the adhesive the lapshear strength
decreases monotonously.

Table 14: Effect of filtration on the bioadhesive yield and lapshear strength for
paperboard samples

 

 

 

 

° ° L shear
DDGS NaOH Urea Time Pressure F‘ltratm” Yield ap
. <y strength
(1:) (g) (g) (m) (atrn) Mode 1 0) (psi)
30.0 4.2 4.2 15 1.6 Vacuum 67 127 :l: 7
30.0 4.2 4.2 15 1.6 Squeeze 85 111 i 7
30.0 4.2 4.2 15 1.6 nil 100 80 i 12

 

 

 

 

 

 

 

 

 

 

64

1.18 Thermal gravimetric analysis

Thermo gravimetric analysis estimates the weight loss with increasing temperature.
It measures the thermal stability of a material. It helps estimating the temperature up to
which the material can be safely used. Weight loss data at different temperature of DDGS
along with other natural fibers are shown in the Table 15. From the percent weight loss
data it is evident that DDGS when dried becomes thermally very stable up to 200 °C. The
residual fibers obtained after extracting bioadhesive had similar thermal stability as kenaf
or maple fibers. The thermal plot of their weight loss versus temperature are shown in the
Figure 23. Another significant observation as evident from the thermal stability data is
that dried DDGS has highest char yield in present case the char yield of dried DDGS is
twice more than that of the kenaf fibers. From the derivative weight loss plot, shown in
Figure 24, the onset of degradation point of dried DDGS fibers is around 250°C which is
slightly less than the other natural fibers. As regards bioadhesive, its thermal stability in
contrast to DDGS and residual fibers are shown in the Figure 25. The data in the Table 15

suggests that bioadhesive is suitable for applications up to 200°C.

65

110 .

 

 
  
  

 

 

Kenaf

90 - . . _ . c/ DDGS dried

DDGS undried
7° “ Fibers after bioadhesive
50 - Maple
30 1
101 I T ' I I r ”nu-.7

0 1 00 200 300 400 500 600

Figure 23: TGA plot of weight loss versus temperature for natural fibers, DDGS,
and residual fibers

66

1.5

   

Kenaf
1.2 - \; E
Maple \
0.9 I E i
Fibers after bioadhe ;
0.6 1

DDGS drled

0.3 I

 

 

 

Figure 24: TGA plot of derivative weight loss versus temperature for natural fibers,
DDGS, and residual fibers.

67

-u
‘l
l

h.

 

   
   
  

 

 

   
 

 

 

 

100 7‘ x ''''''
Dried residual fibers
8 so -« . . .
3 Drled bioadheswes
E 60 1 Dried DDGS
.9 \H/
o “s
3 40 - .......
,\° .
20 1
0 "F"— " T I ‘ I I ’l ‘ I
O 100 200 300 400 500 600

Temperature (°C)

Figure 25: TGA plot of weight loss versus temperature for bioadhesive, DDGS, and
residual fibers

Table 15: Percent weight loss at different temperatures for natural fibers, DDGS,
and residual fibers

 

 

 

 

 

 

 

 

Fibers % Weight Loss at:
100 °C 200 °C 300 °C 400 °C
Kenaf 6 6 10 40
Maple 5 6 10 50
DDGS dried 1 2 14 46
DDGS 4 10 23 50
Residual Fibers 5 6 12 51

 

 

 

 

 

 

68

1.19 Elemental analysis

Elemental analysis was conducted in order to estimate the amount of proteins
present in the DDGS. In the elemental analysis, the sample was evaluated for its carbon
(C), hydrogen (H) and nitrogen (N) contents. Percentage of protein can be estimated form
the CHN elemental analysis by multiplying %N by a factor. For corn proteins the
multiplying factor is 6.25 [102]. DDGS is a rich source of corn proteins, however there is
a substantial difference in the composition of DDGS. It is therefore important to have an
estimate the amount of corn protein in the given DDGS sample. Table 16 shows CHN
elemental analysis of the DDGS and bioadhesive. In the case of bioadhesive, the percent
nitrogen cannot be correlated with amount of proteins, as it is difficult to quantify the

nitrogen from the protein and that from urea.

Table 16: CHN elemental analysis of the DDGS and bioadhesive

 

% Proteins

 

 

Sample %C %H %N
C/oN"6.25)
DDGS 46.09 7.44 4.13 26
Bioadhesive 8.245
(4.2 g NaOH+ 4.2 g 39055 5795 (including '
Urea) N from urea)

 

 

 

 

 

 

 

1.20 Brookfield viscosity

It is important to understand the rheological characteristics of these bioadhesives.

Brookfield viscosity data of the bioadhesives were analyzed. Apart from the denatured

69

proteins there is substantial amount of carbohydrates in the bioadhesive as well. Brook
field viscosity was measured as a function of shear rate, temperature and solid content.
Data suggests that bioadhesives exhibit a shear thinning behavior for almost all the
temperature ranges and solid content. The solid content of the bioadhesive was varied
from 30 wt% to 50 wt% and the temperature ranged from 25 to 60 °C. Shear rates were
varied from 50 to 1000 see". Based on the yield and lapshear strength, four adhesive
formulations were studied for their viscosity. Below is the Brookfield viscosity data for

various bioadhesive as a function of shear rate, solid content and temperature.

1.20.1 Brookfield viscosity profile for bioadhesive sample 3N3U

Viscosity profile in Figure 26 represents the data for bioadhesive at 50% solid
content at room temperature to 60°C. 3N3U at this solid content shows a very mild shear
thinning behavior. At higher shear rates, more Newtonian behavior is observed. At lower

shear rates for 25°C and 40 °C the data almost overlapped.

0256 cI40C 45°C 06°C

 

 

 

 

:E‘ 10000 '1

O

0

.3A 2 2 2 U a

'2 §1000 ‘ t . 3 :

0"

If:

X

8

5 100 . - e
10 100 1000

Shear rate (3")

Figure 26: Brookfield viscosity profile for sample 3N3U at 50% solid content at
room temperature to 60°C

70

Viscosity profile in Figure 27 represents the data for bioadhesive at 40% solid content at
room temperature to 60 °C. As the dilution is increased, the shear thinning behavior is
more pronounced. The viscous response of the bioadhesive looks overlapping for

temperature responses at 25 and 40° C for all shear rates.

(>250 c14°C 450C 960C

 

 

21mm1

3

E‘

0 e

8 g i ‘f’ 0’ 9

3 1000‘ 0 e ‘1 a

> O .

72

9

'2

0

g 100 a . -—.
10 100 1000

Shear rate (3")

Figure 27: Brookfield viscosity profile for sample 3N3U at 40°/o solid content at
room temperature to 60°C

Viscosity profile in Figure 28 represents the data for bioadhesive at 30% solid
content ranging from room temperature (25 °C) to 60 °C. Lower shear rates show shear
thinning behavior. However, at higher shear rates, more Newtonian behavior was
observed. The shear thinning was pronounced at lower temperatures and is diluted at

elevated temperatures.

71

025C 04°C 450C 960C

 

 

3‘ -

.3 1000

O

3 9

u; '3 I Q 9

2 3100 e . ? f

0 v

If:

X

0

g to a. . .
10 100 1000

Shear rate (8")

Figure 28: Brookfield viscosity profile for sample 3N3U at 30% solid content at
room temperature to 60 °C

1.20.2 Brookfield viscosity profile for sample 3N3Uatm

Viscosity profile in Figure 29 represents the data for bioadhesive at 50% solid
content at room temperature to 60 °C. Strong trends of shear thinning over all

temperature ranges and shear rate ranges.

 

 

z, 1'E+°5I o25c -40c tsoc 060C

'8 o s

0

.5 A . _

‘” 1.E+04 ~ "

3 3.. ‘ t z .

in: O a

X

0

2

1' 1.E+03 . a
10 100 1000

Shear Rate(s'1)

Figure 29: Brookfield viscosity profile for sample 3N3U...III at 50% solid content (SC)
at room temperature to 60°C

72

Viscosity profile in Figure 30 represents the data for bioadhesive at 40% solid
content from room temperature to 60 °C. Gradual shear thinning behavior is observed at
lower shear rates however; at higher temperatures and shear rates, more Newtonian

characteristic is observed.

025°C I4OOC £5000 0600C

 

 

3‘ __

g 1.E+04

i 0 ° ° ° 0

>2 : : - - -

3 £1.E+03 9 . : : :

I:

x

0

mg 1.E+02 TF'“ ' fl 7
10 100 1000

Shear Rate (3")

Figure 30: Brookfield viscosity profile for sample 3N3Uatm at 40% solid content
(SC) at room temperature to 60°C

Viscosity profile in Figure 31 represents the data for bioadhesive at 30% solid
content at room temperature to 60°C. Little shear thinning and more Newtonian nature is
observed at all shear rates and lower temperatures. At higher temperatures and lower

shear rates shear thinning behavior are more pronounced that fades out at higher shear

rates

73

025C I400 ASOC 6600

 

 

 

3‘

'g 1.E+03

8 ° 0 o o o

'5 ‘6‘ " l . - -

1: 3 1.E+02 -* 0 t 3 t

a: v

E

'3

9 1.E+01 * .__ r #-——-:

m 10 100 1000
Shear Rate(s'1)

Figure 31: Brookfield viscosity profile for sample 3N3Uatm at 30% solid content
(SC) at room temperature to 60°C

1.20.3 Brookfield viscosity profile for sample 3N

Viscosity profile in Figure 32 represents the data for bioadhesive at 50% solid
content at room temperature to 60°C. At lower temperatures, shear thinning is observed
for all shear rates, however at 60°C, at lower shear rates Newtonian behavior is observed

followed by shear thinning at higher shear rates.

74

 

 

025C I40C A500 0600

E 1.E+05 ~

to

8 o

.2 A °

>

3 §1£+04 ~ _ .

a v ‘ p I .

'52 t o i A =
O

E, 1.E+03 4% — I T

10 100 1000
Shear Rate (3")

Figure 32: Brookfield viscosity profile for sample 3N at 50% solid content (SC) at

room temperature to 60°C

Viscosity profile in Figure 33 represents the data for bioadhesive at 40% solid

content at room temperature to 60 °C. Clear trend of shear thinning was observed over all

temperature ranges and shear rate ranges.

75

025C I400 A500 060C

 

 

 

 

E" 1.E+04 '1 o

m o

O o

.2 °

> a - .

2 3 ‘ - I

:3-3 " ° : . '
o

g 3 A

O o

5 1.E+03 r - I 1

10 100 1000

Shear Rate (3")

Figure 33: Brookfield viscosity profile for sample 3N at 40% solid content (SC) at
room temperature to 60°C

Viscosity profile in Figure 34 represents the data for bioadhesive at 30% solid
content evaluated from room temperature (25 °C) to 60 °C. Strong trend of shear thinning
was observed over all temperature ranges and shear rate ranges. At higher shear rates, the

Newtonian like behavior was observed.

76

0250 I400 A500 (>600

 

 

Q 1.E+03 —

m o

8 . ’ 9 e

.2 A '

> m A I _

E?” i 2; Z '
A

‘2? ° <>

5 10E+02 “i." ‘w' ’ ‘ r ‘ —1

10 100 1000

Shear Rate (3")

Figure 34: Brookfield viscosity profile for sample 3N at 30% solid content at room
temperature to 60 °C

1.20.4 Brookfield viscosity profile for sample 3Natm
Viscosity profile in Figure 35 represents the data for bioadhesive at 50% solid
content from room temperature to 60 °C. It is difficult to predict the trend however; at 40

°C a mild shear thinning behavior is observed.

77

(>250 U400 A500 0600

 

 

Q 1.E+05 ~

3 o

8 u

'51; . ? °

2 31.304 1 . .

g V

x

8

35 1.E+03 ~ e ——_-1———~1
10 100 1000

Shear Rate (3")

Figure 35: Brookfield viscosity profile for sample 3N“... at 50% solid content at
room temperature to 60 °C

Viscosity profile in Figure 36 represents the data for bioadhesive at 40% solid
content from room temperature to 60 °C. At low shear rates, a shear thinning behavior

was observed.

78

0250 I400 A500 0600

 

 

r? 1.5+04 q
§§1.E+03- : g 1 t Z
2 V
:5 L
o
.. 1.E+02 —— a” e, ._..-.._W___j
m
10 100 1000
Shear Rate (3")

Figure 36: Brookfield viscosity profile for sample 3N“... at 40% solid content at
room temperature to 60 0C

Viscosity profile in Figure 37 represents the data for bioadhesive at 30% solid
content at room temperature to 60°C. At room temperature, Newtonian behavior was
observed at lower shear rates. At higher temperatures and lower shear rates strong shear

thinning trends are observed; however, at higher shear rates shear thinning is mild.

79

0250 I400 A500 9600

 

 

 

E" 1.E'|'03 ‘1

a

O

0

.2 A 0 ° ° 0 o

> a

'U I

'5 3 I I . .

I: A

g . g l ‘ ‘

2 ' . .

m 1.E+02 —4———--—~ -- . - - —a
10 100 1000

Shear Rate (5")

Figure 37 : Brookfield viscosity profile for sample 3Natm at 30% solid content (SC)
at room temperature to 600C

1.21 Fourier transform infrared spectroscopy

Fourier Transform Infrared (FTIR) spectroscopy was conducted to analyze the
effect of chemical modifications on DDGS and resulting bioadhesive. Figure 38 shows
the transmission spectra for DDGS and bioadhesive 3N3U and 3N3Uatm. All the samples
were dry when evaluated for FTIR spectra. In the Figure 38 there is a broad peak at 3288-
3343 cm'1 this is characteristic of polymeric OH. As we know that in DDGS and
bioadhesive there is presence of polypeptide and polysaccharides. Thus, this peak is a
combination of both. The peaks at 2921 cm-1 and 2854 cm-1 are due to the methyl and
methylene. In the spectra of DDGS, at 1743 cm", there is a characteristic peak of
carbonyl. This peak is shifted towards 1634 cm'1 this is due to the hydrolysis of carbonyl

groups to C00' . In the fingerprint region the peak ranging from 1150 to 1000 there is

80

characteristic of C-O-C stretching. This is indicative of the presence of polysaccharides.
This peak disappears in the case of adhesive prepared under atmospheric conditions
which suggests that glycoside linkages present in the polysaccharides are affected.

Therefore there should be reduction in the molecular weight of carbohydrates present.

81

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82

EX.

Chapter - Conclusions

Bioadhesive derived from DDGS is an attempt for making the corn ethanol
sustainable. Bioadhesive is a combination of corn polysaccharides and proteins
that makes it an inherently biodegradable.

Presently for paper and paperboard packaging more than half of the demand is
met by starch based adhesives mostly derived from corn. The DDGS based
adhesive is intended to find an alternative to the conventional starch adhesive.
Bioadhesive has been tested on the paperboard the results prove that the adhesive
is strong enough to meet the purpose. The mode of failure in paperboard samples
shows fibers cohesive failure.

Unlike starch based adhesive, the DDGS based bioadhesive is not susceptible to
microbial attack. This was based on the observation of stored samples in a glass
bottles. The starch sample after 4 days gets degraded characterized by the high
flowability mixture starting from initial thick paste. In contrast, bioadhesive did
not show the drop in viscosity (based on visual observation) even after six
months.

The lapshear strength on paperboard suggests a comparable strength of
commercial wheat starch based adhesive and DDGS based bioadhesive, however
in case of wood the starch adhesive was superior. .
Based on the TGA results the thermal stability of bioadhesive was above 200 °C

this suggests DDGS based bioadhesive application over a broad temperature

range.

83

> Protein content in the bioadhesive was about 40 % by weight, this makes it a
hybrid bioadhesive that has good spreadability even at 50% solid content. While
in the case of starch, even a 10% solution was too viscous.

> Rheological properties of bioadhesive when evaluated as a function of shear rate,
solid content and temperature suggests that they exhibit shear thinning behavior
almost over all temperature , shear rates and solid content.

> There are growing environmental concerns due to very high macro-nutrients in
DDGS that limits its use as animal feed. Various factors such as high phosphorus
content, mycotoxin contamination, lack of flowability and energy returns, just to
name a few, were studied to understand the sc0pe of utilization and market of
DDGS. Many environmental issues associated with DDGS can be tackled through
value added applications like biobased material pathways.

> Shelf life of DDGS is small thus unmanaged DDGS can lead to environmental
hazard that can raise question marks on the sustainability of bioethanol derived
from com.

> Utilization of DDGS as value added materials helps to maintain the balance
between food, fuel and biobased materials.

> Changing gears from hydrocarbon economy to carbohydrate economy shall

ensure nation’s energy security.

84

V

V V V V V V

Future Recommendations

To derive lingo-cellulose ethanol from the residual fibers and DDGS

Estimation of molecular weight and its distribution is critical to predict
rheological characteristics.

Chemical separation of complex DDGS to obtain various value added chemicals
Chemical modification of adhesive to make it less alkaline and improve color
Infestation study of the bioadhesives

Microbial degradation of adhesives upon storage.

Effect of humidity on the lapshear strength.

In order to quantify the sustainability parameters it is important to conduct life

cycle analysis of DDGS.

8S

10.

ll.

12.

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93

Appendix 1

The US total energy demand and their fuel wise consumption pattern (after ref. 11)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Year Total Fossil fuels Coal Natural Petroleum Renewable Nuclear
energy (petrolemn Gas
+ coal +
natural gas)
2001 97 83 22 23 38 5 8
2002 98 84 22 24 38 6 8
2003 98 84 22 23 39 6 8
2004 101 86 22 23 41 6 8
2005 101 86 23 23 41 7 8

 

94

 

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