A STUDY ON‘ WINDROW COMPOSTING
WiTH A 50“. SHREDDER

The-SE;- in: the Degree cf M. S.
MECHIGAN STATE COLLEGE
Shioxs'ho, Kw
195:1

 

This is to certify that the

thesis entitled
A Study On E'Jindrow Composting 37y A Soil Shredder
presented by
Shi 'v-Jho Kao

has been accepted towards fulfillment
of the requirements for

AL— degree in M1733???” ” I

:?

Major professor

Date M. M ”54

0-169

 

 

 

)V1£SI_J RETURNING MATERIALS:
Piace in book drop to
LIBRARIES remove this checkout from
4—3—11... YOUY‘ Y’ECOY‘d. FINES_ Will

be charged if book is
returned after the date
‘ stamped beiow.

 

 

 

 

 

 

 

 

A STUDY ON WINDROW COMPOSTIN G

WITH A SOIL SHREDDER

By

Shi -who , Egg

A.Thesis
Submitted to School of Graduate Studies of Michigan
State College of Agriculture and Applied Science
in Partial Fulfillment of the Requirements

for the Degree of
MASTER OF SCIENCE

Department of Sanitary Engineering

lQSh

Acknowledgment

Acknowledgment is extended to Dr.
R. F. McCauley for his helpful
guidance and assistance in connection

with this thesis.

swam

ii

ABSTRACT

This thesis is a study on windrow composting with a soil
shredder. The study was conducted for the purpose of evaluating the
major factors involved in the windrow composting of solid organic
wastes. An equally important consideration was that of establishing
the optimum.value and practical range of each major factor.

Experiments were made with unturned'windrows and with windrows
turned every third day, every second day and every day; The materials
used for study were garbage from the city of East Lansing and dewatered
sewage sludge from the Saginaw, Michigan sewage treatment plant.

Unturned windrow piles showed a long composting period and were
accompanied with odor and fly nuisance; the piles turned every third
day, every second day and every day required 18, 1h and 9 days reSpect-
ively for completion and were without odor or fly nuisance.

The tests used for judging the composts were temperature, pH,
moisture content and percentage of color transmittance. Of these
tests, color transmittance seemed to be most applicable as a yardstick
of windrow composting.

This thesis is a.preliminary study of windrow composting in warm

seasons and results here showed that continued research is well warranted.

TABLE OF CONTENTS

ACKNOWLEDGMENT

ABSTRACT OF THESIS

TABLE OF CONTENTS

LIST OF TABLES

LIST OF ILLUSTRATIONS

Composting athichigan State College ...

and.Particle

Klett-Summerson Calorimeter .

SECTION

I. Introduction . .

II. Review of Literature . .

III.

IV. WindrOW'Composting. .

V. Theoretical Consideration.
Seeding . . .
Moisture Content
Aeration and Moisture . .
Hydrogen Ion Centration .
Temperature.
Color Transmdttance.
Carbon-Nitrogen Ratio

VI. Instrumentation and Equipment.
Choice of Instruments
Other Equipment . . .

VII.

Experimental Procedures and Results.

Experiment 1. . .

Experiment 2
Experiment 3
Experiment h
Experiment 5
Experiment 6

Page

ii

iii

iii

 

 

59.2.!!! flit-Ell. . .‘ihn

SECTION

VIII.

IX.

X.

XI.

Discussion .

Summary and Conclusions. .

Bibliography .

Appendix .

TABLE OF CONTENTS (Cont'd)

Page

55

61
62

iv

LIST OF TABLES

TABLE Page
I A Comparison of Composting
Processes . . . . . . . . . . . . . . . . A
II Composition (wet weight) of Garbage
During the Period of January - June
19 5h 0 O O O O O 0 O O C O O O O O O 0 O I 8
III The Rate of Bacterial Activity
During the First 2h Hours, as
Shown by Temperature. . . . . . . . . . . 2h
IV Initial and.Final Percentage

of Transmittance in Experiment 3. . . . . 33

V Summary of Methods of Treatment
and Material'Used in Experiment h . . . . 36

VI Initial and Final Analysis of
Material Composted in.Experiment h. . . . 37

VII Summary of Methods of Treatment
anthaterial'Used in Experiment 5 . . . . #2

VIII A Comparison of Temperature Change
in Experiment 5 . . . . . . . . . . . . . #2

IX Summary of Methods of Treatment
and.Material Used in Experiment 6 . . . . #8

LIST OF ILLUSTRATIONS

Figure

l.

10.

ll.

l2.

13.

1h.

Klett-Summerson Photoelectric Colorimeter.

A Schematic Diagram of ICIett-Summerson
Photoelectric Colorimeter. . . . . . . . .

Kemp Soil Shredder Used in Windrow Composting

Studie 8 O O O O O O O O O O O O O O O O O 0

Details of Roughage Cutter in Kemp
Soil Shredder. . . . . . . . . . . . .

Mitts and Merrill Type A Hog Grinder
Used for Grinding Coarse Material .. . . . .

Ray-Mo Grinder Used for Grinding
Fine material. 0 O O 0 O O O O O O O C O 0 O

A Windrow Pile With 2-3 Feet High and 12-20 Feet

Long 0 I O O O O O O O O I O O O O O O I O O

The Temperature Curves of Composting Material
in merment l. O O O O I O O O O O O I O O

The Effect of Turning Every Third Day on the
Temperature of Composting Material . . . . .

The Effect of Turning Every Third Day on
the Moisture of Composting Material . . . . .

The Effect of Turning Every Day on the Temperature

of Composting Material in Experiment 3. . .

The Moisture Curve of Composting Material in
Experiment3.........t.......

The Ash Curve of Composting Material in
Experiment3..............

The Oxidation-Reduction Potential Curve of
Composting Material in Experiment 3 .. . .

Page
Ike

15

16a

18

19

22

23

27

3O

31

32

32

vi

LIST or ILLUSTRATIONS (Cont‘d)

Figure

15. The Color Transmittance Curve of Composting
Material in Experiment 3 . . . . . . . . . .

16. pH and Temperature Curve of Composting
Material in Experiment 4 . . . . . . . . .

l7. IMoisture Curves of Composting Material
in Experiment h. . . . . . . . . . . . . . . .

18. Green.Filter Transmittance Curves of
Composting Material in Experiment 1+. . . . . .

19. Effect of Turning Every Second Day on the
Temperature and.pH of Composting Material
in Experiment 5. . . . . . . . . . . . .

20. Moisture Curves for’Mid Depth of Composting
Material in Experiment 5. . . . . . . . .

21. Green.Filter Color Transmittance for'Mid Depth
of Composting Material in Experiment 5 . . .

22. Temperature Curves for Mid Depth of Composting
Material in Experiment 6 . . . . . . . . . . .

23. {Moisture Curves for Mid Depth of Composting
Material in.Experiment 6 . . . . . . . . . . .

2h. pH Curves for.Mid Depth of Composting Material
in Experiment 6. . . . . . . . . . . . . . . .

25. Green.Filter Color Transmittance for Mid Depth

of Composting Material in Experiment 6 . . . .

Page

35

39

Al

A3

#5

M6

49

51

52

53

vii

 

 

. is...“

 

SECTION I

Introduction

 

In China, both on the mainland and on Formosa, difficult problems
in public health sanitation and soil conservation exist. These problems
are due to low health standards and poor farming practices. For centuries,
China has faced the problem of the disposal of human excreta in the heavily
populated cities. The problem of maintaining the soil fertility in order
to grow the crops needed for China’s huge'pOpulation is also very serious.
The loss of the mainland, due to the Red invasion, resulted in loss
of trained personnel in all fields, including sanitation. During the past
ten years, the Free China government on Formosa has enrolled several per-
sons for advanced training in Public Health and Sanitary Engineering. This
writer was sent to the United States under this program to study composting.
Composting is of great importance to Formosa. Organic wastes from
Formosa‘s cities are a major vehicle in the spread of intestinal diseases.
The composting of rI'arbage and human excreta offers an answer to the prob-
lem of sanitation and to the problem of restoring organic matter to the soil.
The windrow composting process promises Formosa a feasible disposal
Inethod for wastes and human excreta. The process is not highly mechanized;
only a grinder and soil Shredder are needed. Windrow composting is es-

‘pecially suitable for such places as Formosa where labor is cheap and the

climate is warm.

 

 

 

 

 

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SECTION II

Review of Literature

 

Composting is ”the production from organic wastes, through the
agency of microorganisms, of a relatively stable humus which may bene-
ficially be used on agricultural soils.”l It is a natural biological
process which proceeds most rapidly under optimum environmental conditions.
Important considerations are temperature, moisture, particle size, and the
composition of raw materials.

For centuries, man has been taking organic wastes and converting
them into a useful fertilizer by the natural process. This procedure re—
quires a long time, usually more than a year or two, although a good
product can be produced. Due to a lack of scientific knowledge, the
composting process had always been practiced as an art rather than a
science.

The first important advance in the practice of composting was made
about thirty years ago in India by Lord Howard who systematized the trad-
itional practices and developed the Indore Process. The time required
for the process to go to completion was still quite long, usually in ex-
cess of six to eight months. Since that time, various processes have been
designed and patented to shorten the detention period of composting, as
listed in Table I.

Over the past five years considerable work on a highly scientific
level has been done in the development of important data to reduce the

detention period of composting. The research carried on at Michigan State

College and other institutions throughout the world should result in the
design of a modern, efficient, high-rate composting process which will pro-
vide an economical method for disposing of organic wastes and for reclaim-

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SECTION III

Composting at Michigan State College

Research work at.Michigan State College is being done in connection
with (a) a large plant size digester, (b) twenty-two completely control-
led oneapound laboratory units, (0) a prototype Crane digester, and
(d) windrow composting.

The large plant size digester used in.Michigan State College is a
modified Earp-Thomas type. It stands twenty-three feet high, is ten
feet in diameter, and is separated into eight decks. The digester is
insulated with two inches of foamgdass brick covered with tar’paper.

Raw garbage from.East Lansing (Specific constituents are listed as Table
II.) is delivered to the plant in trucks and dumped indoors on a concrete
floor. Tin cans and bottles are removed. The garbage is then ground
and conveyed by'a bucket-type conveyor to a storage and dewatering tank
where the moisture content is reduced from about 75-80 per cent to about
55-65 per cent.3 The material remains in this tank for one to six days
for dewatering by gravity and then is conveyed to the t0p deck of the
digester. .A slowly rotating vertical shaft passes through each deck.
.A.cross arm.is mounted on the shaft in each deck and plows are attached
to the cross arm. These plows aerate and mix the material and drop it
from.deck to deck gradually. The material takes two to three days to
jpass through the digester. This procedure produces a stable organic

compost.

The one-pound laboratory units are lucite plastic digesters
mounted in temperature controlled water baths. The material in these
gas-tight digesters is mechanically aerated by slowly revolving arms
which are mounted on a central driving shaft. Oxygen uptake, carbon
dioxide production, and various other chemical yardsticks are measured.

The prototype Crane digester is a horizontal digester unit, one-
sixteenth of the designed four deck size. The material is aerated and
moved by a series of paddle type screw conveyors. Designed as a con-
tinuous flow operation the material is charged in the top deck and
gradually moved and aerated” lMaterial drops from deck to deck. Dis-
charge at the bottom is of a composted.material. The detention time
may be adjusted by changing either the pitch of the aerating paddles
or by changing the gear ratio of the driving mechanism.

The windrow composting work reported here has been carried on
during the last six months. Ground and unground garbage as well as
sewage sludge cakes have been shredded on the ground in windrows by
a soil shredder. Piles have been turned every day, every other day,
or every third day. Different readings have been tested. A.series
of variables, such as temperature, moisture, ash, pH, 0.R.P., color

'transmittance and bacterial population have been measured.

TABLE II

Composition (wet weight) of Garbage During

the Period of January - April, 1951+*

 

 

 

 

 

 

 

 

 

 

 

 

 

*‘I‘his table taken from a thesis by Williams
G. Turney on "A Study Concerning the Estab-
lishment of a Yardstick for Garbage Digesti
by Composting."

"arbage Constituent Per Cent

Paper 18.5

Meat, Fat, Fish, Peanuts, Eggs,

Cheese, Milk, and Cream 6.8

Citrus Fruits 18.5

Other Fruits, Bananas, Grapes,

Tomatoes ,_Apples L etc. 1.1+

Green Vegetables, Celery, Corn husks,

Melons, Cabbages, Lettuce ,Fetc. 11.6

Coffee Grounds and Tea Leaves _§.l

Bread, CakeLMacaroniL Cereal, etc. 9.2

Potatoes, Beans, Corn, Onions, Beets, etc. 11+.11-

Miscellaneous, Egg Shells, Nuts,

Bottle caps, Bones, Rags, Rubber, etc. 8. 5
100-0

on

 

SECTION IV

Windrow Composting

 

The windrow composting process is an old method with a new name.
As has been previously stated, composting in its most primitive form
has been practiced by farmers and gardeners for many centuries. Their
procedure has been to pile vegetable matter and animal manure in some
available open space and to allow it to ferment naturally until ready
for application to the soil. This type of composting is without control
and introduces flies, rodents, odors, and sometimes communicable diseases.
A long detention period is necessary.

Because of research done during the last few years, windrow com-
posting today is no longer an art but a science. The pile is turned
periodically to eliminate the offensive odors through aeration. The
temperature which results is sufficient to kill all disease-producing
organisms. Humus can be produced within a few days or weeks.

The study reported in this thesis was made by composting organic
material on sandy soil. The ground or unground materials were shredded
by a movable soil shredder and placed in windrows. To form the piles
a metal plate was set up a short distance from the shredder to act as
a. shield. This kept the lighter particles from flying past the end of
the pile.

Temperature measurements and other tests were made at each turning
with the shredder or fork for the purpose of determining and evaluating
the major factors involved in successful composting of solid organic
wastes and to establish the optimum practical range of variation of each

major factor.

10

SECTION V

Theoretical Consideration

Because composting is a biological process, environmental factors
influencing the activities of microorganisms determine the speed and
course of the composting cycle. Such factors include seeding, moisture
content, aeration, hydrogen ion concentration, temperature, particle

size, color transmittance, and initial carbon-nitrogen ratio of food

material .

Seeding

Although the decomposition of organic material depends upon bac-
terial activities the process appears to proceed most rapidly under ther-
mophilic aerobic conditions. Seeding does not seem to be an essential
part of a practical process for composting. Mesophilic and thermophilic
organisms indigenous to garbage and sewage sludge are probably sufficient

to carry on the composting process when environmental conditions of

moisture and aeration are suitable .

Moisture Content and Particle Size

The moisture content of a raw material for composting is a relative
thing. Two materials with the same initial moisture content but with
different particle size may show different degrees of decomposition if
other conditions remain the same. The coarse material has less surface
area but has more voids in contact with air than the fine material, and

rapid decomposition is carried out by facultative aerobic organisms with-

out odor. Particle size of material is controlled by grinding. Ideally,

the more minute the particle, the more susceptible it is to the bacterial

ll

or fungi attack because of the greater surface exposed. Therefore,
especially for windrow composting, coarser particles seem indicated

at the beginning of the composting process with finder particles being
desirable at the middle stage when the moisture has dropped to some ex-
tent.

Aeration and Moisture

 

Aeration supplies the oxygen required by aerobic bacteria in
carrying out their activities. An aerobic process is more efficient
than an anaerobic one in the decomposition of organic materials. For
these reasons, compost piles should be turned frequently. Too low a
moisture content deprives microorganisms of the water needed in their
metabolism and consequently inhibits bacterial activity. Hence, con-
sideration should be given to the per cent moisture at which the turning
of the pile should be st0pped unless additional moisture is added.
Hydrogen Ion Concentration

Most bacteria thrive at neutral and moderately high pH values,
and fungi at low to neutral values. In composting, the acid producing
'bacteria are the first to appear and a significant drop in pH is always
noted. An increase in.pH then occurs, probably due to the breakdown of
acids and the release of ammonia by protein decomposition. In the final
stages, when the temperature begins to decline, actinomycetes become
jpredominant with other mixed populations, and a high.pH is observed.
{The pH value is very useful for indicating the change of composting of
garbage during the initial stage but is not so helpful near the final
stages. Color transmittance may prove to be a useful indicator for

composting in the final stages.

12

Temperature

 

The composting temperature results from bacterial activity. Bacteria
most readily obtain energy through the breakdown of sugars, ultimately in
the form of glucose. Excess energy above the requirements of the bacteria
is released and accumulated as the heat of the composting.

Bacteria are divided into two major types: Mesophilic and Thermophilic.
The Mesophilic type of bacteria exist at temperatures from 8° to #500. and
Thermophilic bacteria grow and thrive in temperatures from #50 to 65°C. or
even higher.1+ Therefore, the temperature reached largely determines which
of these two types of bacteria will predominate. Consequently, temperature
becomes an important control and an aid in judging the course of a compost
pile.5
Color Transmittance

Glasstone6 (Textbook of Physical Chemistry) has explained color
phenomenon. His remarks may be summarized as follows: "The absorption
spectrum of a substance is related to its color, but when absorption is
in the ultraviolet only, the substance will be colorless. 'Unsaturated
eleCtrons are less firmly bound than those forming linkages, so structural
changes in a molecule cause the band to shift to regions of longer wave
length. Two or more unsaturated groupings often enhance one another so
that visible color is produced. For instance, stilbene itself, C6H5(CH=CH)
0635: is colorless, but as the number of -CH'CH- group is increased, the
color passes through yellow to green and orange. On the other hand, the
introduction of a -CH2 group in the unsaturated chain destroys the conjug-
ation, and is accompanied by a shift of the absorption band to shorter
'wave lengths to render a substance colorless. This phenomenon.may be

illustrated by reference to C6H5(CH=CH)kC6H5, which is greenish yellow,

while 0615CH2(CH:CH)06H5 is colorless."

13

The color of garbage-compost changes in solution from light gray
to dark brown. This may be due to the increasing number of -CH=CH- groups
in its electronic structure during the period of composting. On the other
hand the color change from.dark gray to light gray observed when composting
sludge may be caused by introduction of a -CH2 group in the unsaturated

chain, thus causing some shift of the absorption band.

Carbon-Nitrogen Ratio

Carbon-nitrogen ratio is expressed by dividing the percentage of
carbon in the sample by percentage of nitrogen. If this ratio is large
(say 100) the C/N is spoken of as wide, whereas if the ratio is 10 it is
described as narrow. It has been suggested that a narrow figure indicates
that the nitrogen is immediately usable and composting may not be called

for. If the ratio is wide, composting is necessary until the ratio is

narrowed.

14

SECTION VI

Instrumentation and Equipment

A series of tests were run on each compost sample. Each of these
tests involved the use of a different instrument. Some of the laboratory
instruments that were used were the Klett-Summerson photoelectric color-
imeter, Beckman Model H-2 pH meter, commercial balances and drying ovens.

A special type calomel cell and platinum electrode were constructed
and used with the pH meter for measuring oxidation-reduction potential.
Choice of Instruments

The IQett-Summerson photoelectric colorimeter7,8,9was chosen for
use in measuring color change observed during composting. The use of
pH, C/N ratio, etc., also have been suggested as good compost yardsticks.
However, pH is not so helpful near the final composting stage and C/N
ratio is time consuming.

The photoelectric colorimeter is one of the newest improvements in
the design of colorimeters. Errors due to the personal characteristics
of each observer have been largely eliminated. It is convenient to carry
and easy to run even though the observer is a beginner.

Klett-Smmnerson Colorimeter (Shown in Figure 1) .

A schematic diagram of Klett-Summerson photoelectric colorimeter is
shown in Figure 2. The light source, in the lamp housing, is a lOO-watt
tungsten projector lamp. The incident light passes through a lens and a

suitable color filter F which is used to transmit light of the proper wave

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length range. The light falls upon the solution contained in a colori-
meter tube E and the light transmitted through the solution reaches the
Barrier layer cells. The generated current is measured on the scale
reading B, which is graduated from 0 to 1,000.

The scale B is a most important part of the colorimeter. It has
been designed so that the scale reading is directly proportional to the
concentration of the substance being determined. The scale reading is
a measure of and is proportional to the optical density of the colored
solution as determined by the photoelectric cell. Since the optical
density is theoretically proportional to the concentration of colored
substance (Lambert-Beer's Law) the scale readings are likewise proportional
to the concentration under the same conditions.

Other Equipment

1. Kemp Soil Shredder - Figures 3 and 1+, shows the installation
used in the field composting studies. It includes roughage cutter, in-
dustrial type gasoline engine with multiple U-belt drive, and with a
mesh basket so constructed that the chopped material can be scattered in
a windrow of approximately 20 feet apart from the shredder and distribute
it uniformly.

2. Mitts and Merrill Type A Hog Grinder - Figure 5, shows the
M. & M. grinder used in the High-rate composting plant at Michigan State
College. It includes several knife edges in a running steel cylinder as
a roughage cutter, and an electric motor with a common belt drive. The
material through the M. 8: M. grinder is much coarser than that from
Ray-Mo grinder.

3. The Ray-Mo Grinder - Figure 6, shows another type of grinder

(Ray-Mo) which was much used in windrow composting studies. It consists

16a

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17

of two screw conveyors, which are used to transmit the raw material to
the cutter and the ground material to a truck from the cutter, and the
high speed blade cutters which are driven directly by an electric motor.
The ground material from the Ray-Mo grinder is much finer than that from

the M. 8c M. grinder and is usually smaller than one-inch size.

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21

SECTION VII

Experimental Procedures and Results
Experiment 1

The first series of tests was preliminary in nature and intended to
give information on the effects of temperature changes and to study fly
nuisance with composting piles having no treatment other than grinding.
Three piles were built during mid-June. The first pile was built with
8,060 pounds of Ray-Mo ground raw garbage shredded together with 700 pounds
of end products from the High-rate composting plant. Moisture content of
the composted seed material was about 30 per cent. The second pile con-
tained 7,835 pounds of Ray-Mo ground garbage and the third pile 5,625
pounds of unground garbage with high paper content. Each of these piles
was shredded once With a Kemp soil shredder at the start and received no
further turning. The shape of these piles was trapezoidal in section,

3 feet at top and 5 feet at bottom. The heights were 2 to 3 feet and
lengths 12 to 20 feet (as shown in Figure 7). Weather was hot and dry.

The experiment was continued for 25 days until a layer of crust was
formed on the surface of each pile. The effect of various environmental
conditions on the rate of bacterial population and activity are illustrated
by the temperature reached during the first 21+ hours, as shown in Table III.

The similar temperature rise (as shown in Figure 8) observed in piles
No. l and 3, shows that the bacterial population indigenous to garbage was

just about as effective as that of the end products from the High-rate

plant .

22

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3. ANSI.

21+

TABLE III

The Rate of Bacterial Activity During the
First 2h Hours. As Shown by Temperature.

Ambient Temperature

 

 

 

Pile Air Temp- 8f Compost,
No. Material Treatment eratureL C C
’1. $0601? Ray-Mo ground Shredded with 26 50
raw garbage; 700# Kemp shredder at
e.p.* with 30% start; no turn-
moisture. ing_.
4 . 7,83%g Ray-Mo ground “ 26 El
raw garbage. " "
:3 . 5,—62571f’raw garbage 25 1+6
with high paper " "
content.

 

 

 

 

 

 

 

*e.p. = end product

The material in pile No. 2 showed a somewhat smaller rise in temper-
ature, probably because the voids were largely sealed by the moisture which
was much higher than Piles No. l and 3.

During the first three days, Pile No. 3 proved attractive to birds
because of its undecomposed food materials. After three days, a foul odor
together with considerable larvae was observed in all these three piles.
0n the fifth day, about half of the larvae were dead in Pile No. 3, and
the balance were still active near the pile or immediately below the sur-
face of the pile. The same conditions existed on the sixth day in Pile
No. 2 and the seventh day in Pile No. 1. Several fly traps were constructed
for trapping flies emerging from pile or ground, using h-inch tin cans, with
top and bottom cut away, and 20-mesh screen welded to one end. These were
placed around each pile on the fifth day. From the tenth day on, flies
were trapped continuously until the twentieth day.

At the close of the experiment on the twenty-sixth day, no satisfactory

degree of decomposition was apparent. In the top four inches of each pile

25

a pleasant earthy odor was apparent, while an unpleasant putrefaction
odor existed in the center.

Three and a half months later, the piles were examined after a heavy
rain. Piles No. l and 2 recovered with temperature readings of approximately
l+2OC5 in contrast, Pile No. 3 showed no recovery of temperature and appeared
to be a good compost. This indicated decomposition of Pile No. 3 far ad-
vanced to that observed in Pile No. l and No. 2. The increased decomposition
was probably due to the high paper content and the type of grinding giving
more porosity to the pile and allowing good aeration through its structure.

The experiment demonstrated that:

1. Without turning,a better decomposition can be obtained by composting
coarser material due to the increased porosity of the pile.

2. A windrow composting pile without firther treatment may cause
odor and fly nuisance during the composting period.

3. Unturned piles require a longer time for decomposition.

h. Seeding of such piles is of little value.

5. Larvae are killed at temperatures around 60°C.*

6.

The highest temperatures are reached in the top lL-inch layer of

these unturned piles .

Experiment 2
The second experiment was designed to study the effect of aeration by
turning the pile every third day. One pile was prepared by shredding 6,600
pounds of Ray-Mo ground garbage into a windrow. This was turned four times
during the composting period. The pile was a 3-foot by 5-foot trapezoid,

12 feet long and 3 feet high. A maximum temperature of 67°C in the top

91-52) C was reported by "New Zealand Engineering", Vol. 6, Nos. 11-12.

26

four inches was reached on the sixth day. After the sixth day temperatures
dropped gadually to 25°C until, on the eighteenth day, a finished compost
was produced. The temperature curve is shown in Figure 9.

No larvae appeared during the experiment and no flies emerged from
ground into the traps placed around the pile.

Figure 9 also contains a plot of pH versus time. The pH drop in the
two-inch layer on the ninth day was probably due to some relatively undecom-
posed materials which were moved to the top layer by shredding.

The moisture content on top and bottom layers of the pile had a dif-
ference of 32 per cent as shown in Figure 10. The effect of turning every
third day had little influence on the moisture drop to the bottom layer
of the pile.

Experiment 2 showed that:

1. Turning the pile every third day eliminates foul odors and fly
nuisance.

2. Eighteen days is required for composting when turning every third
day under suitable environmental conditions.

3. High temperatures at 8-inch depth indicate that good aeration can
be obtained by turning every third day.

1+. A declining temperature below lI-OOC, a pH higher than 7.0, a
moisture content less than 55 per cent, and a well composted material with

a good earthy odor may be expected after eighteen days.

Experiment 3

 

In order to determine the relative importance of seeding and turning
in producing a shorter composting period than in Experiment 2, another pile

in windrow shape was prepared for study. 15100 pounds of Ray-Mo ground raw

27

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garbage and 2,000 pounds of end products from Experiment 2 were shredded
together. The pile was aerated with the Kemp shredder every day.

The per cent moisture of raw garbage dropped from 72.6 to 61 when
mixed with the end product. pH dropped from 1+.9 to 1+.8 with a per cent
ash rise from 10.8 to 18.1.

The initial moisture of the pile was relatively low and dropped rapidly
by daily turning. This moisture drop reduced the level below that required
for good composting. Turning of the pile was discontinued after the tenth
day to prevent further moisture loss. Composting period of the pile was
fourteen days.

More extensive tests were made with Experiment 3 than previously;
new tests were percentage of ash, Oxidation-Reduction Potential, and
percentage of color transmittance. Procedures for these tests are listed
in Appendix.

The temperature curve (as shown in Figure ll) for the h-inch depth
rose gradually from 35°C to 61+°C on the eighth day, and then declined to
38°C on the fourteenth day. On the basis of temperature, the compost was
considered to be finished with a declining temperature around 110°C.

Figure 12 represents a plotting of per cent moisture versus time.
This curve shows why it was necessary to stop turning the pile on the
tenth day. The per cent moisture on the ninth day had dropped to 32.
This value was considered a lower limit for bacterial metabolism. A
one-quarter inch moisture penetration was observed after a rain of 0.1.1.
on the eighth day. This indicates that rainfall had little influence on
the moisture content of the pile.

The ash curve as shown in Figure 13 is almost meaningless. It was

found difficult to collect a representative sample free of sand or grass

30

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picked up from the sandy soil during turning. The ash test was there-
fore omitted in the latter experiments.

Figure 11 also shows the pH curve for this experiment. The initial
pH of n.8, dropped slightly on the second day, and then rose gradually
to a figure between 7.0 and 8.0 when composting was finished. This appears
to be a typical composting pH curve. Molds and actinomycetes were found in
the pile during the final stage when pH was high.

The Oxidation-Reduction Potential (abbreviated as ORP) curve shown
in Figure 1h appeared to be a good indicator for pile turning. During this
period of turning from the first to tenth day the curve rose gradually
to a value of -225 milivolts. When turning was stopped on the tenth day,
the curve dropped to -300 milivolts on.the fourteenth day. Although another
rising value ~27O milivolts were observed at the seventeenth day, it is
probably due to the influence of moisture loss and consequently the pile
got more aerated.

The initial and final percentages of color transmittance of 4-inch

samples are shown in Table IV.

TABLE IV

Initial and Final Percentage of Transmittance
with Different Filters in Experiment 3

Filter Used Initial Final
i r
Red Filter

    

Green ter
Blue Filter 1

For best results with the photoelectric colorimeter it was found
:hnportant that the proper light filter be used. Results indicate that

the green filter is most suitable for garbage compost. This filter covers

31+

not only the colored solution of red, yellow, purple, orange and blue7, but
the transmittance curve changes distinctly according to each composting
period. This change in transmittance is also noted with the blue filter
during early stages of composting but little change is noted in later
stages. For this reason the green filter is preferred.

From the curve obtained with the green filter (as shown in.Figure 15),
it appears that the percentage of transmittance changes from an initial
reading of 65-90 to a final reading of around 20.

It was cOncluded from.Experiment 3 that:

1. When moisture content is satisfactory aeration by daily turning
appears to produce good compost within a shorter period than when turned
every third day.

2. Ash is not a good indicator of windrow compost on sandy soil bround.

3. ORP may be a good yardstick for composting and should be investigated
in the future research.

h. A.dec1ining temperature below 50°C and a.percentage transmittance
drop to about 20, with a green filter, may be a good yardstick for judging
the condition of a garbage composting pile.

5. Heavy seeding dropped the initial moisture content to 60 per cent.
This moisture content was found too low to be suitable for continuous every
day turning. The experiment required eighteen days because of low moisture

content.

Experiment h

 

Experiment h was set up to test the effect of seeding and re-seeding,
with or without turning. A series of three piles were prepared as outlined

in Table V.

35

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TABLE V

Summary of Methods of Treatment
and.Material Used in Experiment h

Material

Treatment

 

l.

l933#fRay+Mo Ground Raw Garbage

25%*Seeding with e.p.
from.Experiment 3, turn-
ed every day'with
shredder.

 

II H II

25% Seeding with e.p.
from.Experiment 3, 25%
re-seeding on the hth
day with the same e.p.,
turned every day with
shredder.

 

 

 

25%78eeding'with e.p.
grom.Experiment 3, turn-
ed h times in h days,
turning stopped on 5th

 

 

flay.

 

The experiment was continued for nine

this period the piles were still warm.

36

days, although at the end of

The similar temperature rise and fall and similar color transmittance

in Pile No. l and 2 showed that seeding and re-seeding had very little, if

any, effect on the time necessary to obtain a good end product when the

piles were turned daily.

Pile No. 3, with the discontinuance of turning

after the fifth day,'was not as well decomposed as the other two during

the same composting period.

composted in Experiment h was shown in Table VI.

The initial and final analysis of material

37

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38

The pH of the 8-inch sample of Pile No. 3 was 5.2 after nine days,
indicating that the bottom layer still remained partly composted. The
other two piles, which were turned daily, had the same final pH values
and the material appeared to be well composted even though the temperatures
were still high. The pH curve is shown in Figure 16.

Figure 17 shows the moisture change of these three piles. Re-seeding
caused a one per cent moisture drop at four inches and a six per cent drop
at six inches for Pile No. 2 as compared with.Pile No. l. The discontinu-
ance of turning of Pile No. 3 resulted in a higher moisture content than
for the other two piles.

Curves shown in.Figure 18 represent the change in color transmittance
when using a green filter for 2-, h- and 8-inch depths in Piles l, 2 and 3.
These curves showed a drOp from a value of 70 per cent transmittance to
around 10 per cent near the point of completed product. A.reversal of
this trend and rise to about 20 per cent transmittance is noted during
the final drop of composting. The per cent transmittance of 8-inch final
sample in Pile No. 3 was 52, a figure still far from composted.

Experiment h indicated that:

l. Seeding and re-seeding may not be an essential part of a.practical
process for composting garbage.

2. Discontinuance of turning the pile delayed the composting period
on the bottom layer which was not properly aerated.

3. Color transmittance curves further indicated that this test is
a good indicator of degree of composting.

h. Turning the pile every day reduced the composting time of those

piles to nine days.

39

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Experiment 5

 

Experiment 5 was designed to determine the influence of particle size
and to further study the effect of turning on garbage composting. During

this experiment piles were turned every two days. Methods of treatment
are listed in Table VII.
TABLE VII

Summary of Methods of Treatment
and.Material.Used in Experiment 5

 

 

 

 

Pile

No. Material Treatment

' l,OSO#'RayHMo fine ground raw 10% seeding.

l. garbage, 38# e.p. from High-rate Turned every 2 days
plant. with shredder.
l,OOO# RayaMo fine ground raw 10% seeding.

2. garbage, 38# e.p. from Experi- Turned every 2 days
ment h. with fork.

900# M. 8: M. coarse ground raw 10% seeding.

3. garbage, 38# e.p. from High-rate Turned every 2 days

plant. with shredder.

 

 

 

 

Temperature rise and fall of these piles is shown in Table VIII and

Figure 19.

TABLE VIII

A Comparison of Temperature Change in Experiment 5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IPile Initial High Temperature Low Temperature
2N0. Temp. Reaghed and Date Reached and Date Physical Conditions
'Bin. 690C, 6th day ‘Hin. 1300, 3lst dayerine material turned
1. 32°C Bin. 710C, 8th day Bin. 13°C, 3lst daL with shredder. Heat
built up slowly and
lost slowly.
in. 720g, 7th daL hin. 6°CL 11Ith day Fine material turned
2. 20°C Bin. 72°C, 7th day, Bin. 6°C, lhth day with fork, with re-
sulting é- inch balls.
Heat built up slowly,
lost Quickly.
hin. 70°C, 6th day hin. 16°C, 29th day;_Coarse material turns
3. I 36°C in. 730C, 6th day Bin. 20°C, 29th day_ ed with shredder.
Heat built up quick-
ly and lost quickly.

 

 

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The rapid drop of moisture influenced the temperature drop of Piles
No. l and 3, as shown in.Figure 20. The temperatures of these unfinished
piles built up again when moisture content was restored by heavy rains.
Such results account for the thirty-one days required to complete the
composting process, a longer period than that required for 3-day turning.

Pile No. 3 was turned with a fork and not too thoroughly aerated,
as evidenced by foul odors and a fresh color at the bottom of the pile
before the third turning. Half-inch balls gradually formed as a result
of the fork turning. A rapid temperature rise was first observed, but
this rise was followed by a rapid loss in temperature because of a lack
of insulation.

One advantage of this kind of pile, unshredded, was the capacity to
absorb moisture from rainfall and in this way to maintain a higher moisture
content during the composting period. The disadvantages are:

1. Quick loss of moisture content if no precipitation occurred during
the composting period.

2. The centers of the half-inch balls not completely decomposed.

3. An anaerobic decomposition existed at the beginning, accompanied
with foul odor and slow composting.

The initial h-inch pH of Pile No. 1 was. 5.2. This dropped to 1+.5
and then rose to 9.1 just before the third turning. A.similar condition
'was observed in Piles No. 2 and 3, which had little initial pH drop, if
any. Piles 2 and 3 did not follow the typical pH curve as previously es-
tablished. The pH curves of this experiment are also shown in Figure 19.

The percentage of green filter color transmittance is shown in

Figure 21. This indicates that the raw material of Piles No. l and 3

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started at 90 per cent and finished at about 20 per cent. Pile No. 2
started fran 83 per cent and ended at 11+ per cent. This suggested that
Pile No. 2 still needed additional curing time.

The initial percentage color transmittance appears to change with
the quantity of seeding and with the time of storage before the piles
were started. Seeding with large amounts of end product dropped the trans-
mittance because the end products have a low transmittance naturally.

The garbage decomposed biologically during storage time, with resulting
change in transmittance.

Experiment 5 indicated:

1. With high moisture content during the initial period, coarse
material appeared to be more suitable for composting than finely ground
material. This is probably because the coarse material has better struc-
tural strength and more voids in contact with the air than fine material.

2. The fine material seemed to be more suitable for final stage
composting because the fine material has relatively larger surface area
in contact with air than coarser material.

3. Half-inch balls were formed by fork turning. Such piles were
more readily influenced by outside conditions. Rainfall penetrated the
pile from top to bottom during a rainy period; wind and sunshine reduced
moisture rapidly, and a loss of heat was common due to poor insulation.

Anaerobic decompoisition existed near the center of the balls, accompanied

by a foul odor and less complete composting.

Experiment 6

Experiment 6 was designed to study the composting of raw sludge

#8

cake. Two tons of raw primary sludge vacuum.filter cake* were secured
for study from the Saginaw, Michigan, sewage treatment plant. The material

and methods of treatment used in each pile is listed in Table IX.

TABLE IX

Summary of Methods of Treatment
and Material.Used in Experiment 6

Pile
No. Material Treatment

500# raw sludge cake, 2,000# raw gar- Turned every day with
l. bage, lSO# partially composted garbage. shredder.

l,500# raw sludge cake, 700# raw garbage,
2 150# partially composted garbage.

2,000# raw sludge cake, 150# partially
3. composted garbage.

h

 

 

 

N H II

 

2,700# raw garbage, 150% partially
. composted garbage.

 

 

 

 

 

Temperature changes during the first day varied over a wide range
in the three piles. The highest temperature was 62°C in Pile No. l and
the lowest was 2h°C in.Pile No. 3. This last temperature was the same
as the ambient temperature on that day, as shown in Figure 22. The slow
rise in temperature of Pile No. 3 in the first day was doubtless due to
the sticky nature of the sludge cake. Pile No. 3 was very wet and practic-
ally'voidless after shredding. By the end of the second day the temper-
ature of the sludge pile (Pile No. 3) rose to EHQC, only a few degress less
than the other three piles.

'Unfortunately, the shredder was broken by the sticky sludge cake
at the end of the second day. It was, therefore, necessary to use forks
“to turn all these piles for the next several days. .A slow temperature drop
curve of the sludge pile was maintained, probably resulting from the fork
turning.
'*Saginaw sludge (a primary sludge without secondary'tfieatment): iMonthly '
'variation in filtration rate (Aug.)=7.68-8.h0 lb./ft. /hour; Average filtration
:rate=7.5 lb./ft.2{hour (dry solids). Dosage of chemicals on.Aug. 23: Feel

(dry wt. as Fecl -l.h per cent; Lime (dry wt. as Cao)-5.h per cent. Year y
average dosage of chemicals: Fecl3-l.lI-8 per cent, Lime - 5.60 per cent.

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Half-inch balls were observed in Pile No. 3, but these balls were of an
entirely different composition than those of Experiment 5. These sludge
balls had a hard crust outside and a watery sludge inside. This condition
maintained the moisture content and could be the reason that the temperature
remained at a high level for a long time.

Piles No. l, 2 and h showed a temperature drop to about 20°C due to
the rapid moisture loss on the fourteenth day (as shown in.Figure 23).

The initial pH of Piles No. l, 2 and 3 was high and remained around
8.0 throughout the entire period. The high initial pH value of raw sludge
was due to lime added for filtering. The pH curve of Pile No. R follows
the regular pattern but without any initial drop, probably due to good
aeration at the beginning. The pH curves were shown in.Figure 2h.

One interesting phenomenon noted during this experiment was the
reversal of the percentage of color transmittance as compared to the
results observed with garbage. The green filter value of Pile No. 3 (sludge
composting pile) changed from.high to low at the middle composting stage
and thenrose again to a value much higher than at the beginning. This
relationship is shown in.Figure 25.

Color transmittance of sludge compost changes with a reverse direction
to garbage compost, probably due to the introduction of a -CH2 group in the
‘unsaturated chain which causes some shift of the absorption band in the
sludge substance (See Section V). Though change of color transmittance
of sludge and garbage cannot be compared the changes noted were of value
in recording changes which took place during composting. This could well

be investigated in the future research.

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Experiment 6 suggested:

1. An initial blending of sludge and.partly composted garbage was
useful as a means of increasing its porosity.

2. pH does not seem.a reliable yardstick for judging the sludge
composting because of the small change noted during the course of composting.

3. The change in the per cent transmittance of sludge apparently

varies greatly from that of garbage during composting.

55

SECTION VIII

Discussion

 

Requirements of Ideal Windrow Composting

The time required for windrow composting was, in the main.part,
determined by the degree of aeration through turning. The degree of
decomposition was also affected by particle size and.moisture content.
Therefore, the ideal composting pile may be characterized as follows:

1. Daily turning to secure good aeration.

2. Suitable moisture maintained throughout the composting period.

3. A.material of good structural strength against compaction in
the top layer to keep aeration voids open.

h. .A material of very small particle size with relatively large
surface area to absorb oxygen from the air.

5. Good insulation in the outside layer to speed up decomposition
by thermophilic bacteria.

Experience gained during these experiments showed that a rapid
:moisture loss must be expected.with frequent turnings. Hence aeration
by turning the pile accompanied with suitable moisture adjustment,when
necssary, seems indicated, For windrow composting it may be well to turn
the pile after a rainfall so that the compost can recover some moisture
from the wetted ground.

According to requirements 3 and h, a treatment involving both turning
and grinding may be desirable. Proper turning produces good aeration ac-

companied with heat and moisture loss. If this shredding operation were

56

followed by grinding,an increase in the contact area of composting material
to the air could be obtained without loss of aeration voids.

Insulation on the outside layer of the pile would.make the pile a
closed cell and cause anaerobic decomposition in the inner layers. There-
fore, it would appear that insulation should not be considered unless means
are assured for moving the outside layer to the center of the pile when
turning.

In windrow composting, the insulation usually comes from the pile size
used. Too small size has poor insulation and too large size is always ac-
companied by’a compaction due to weight of the material. In Experiment 2
a pile two to three feet high was well aerated by turning every third day.
It would seem to be possible to build a long windrow pile with a trapezoidal
section of four to five feet high and to aerate every day by turning without
compaction. A.trapezoidal form with an 8-foot base seems convenient for
turning the pile with the Kemp soil shredder.

‘Value of Seeding and Re-seeding.

Although Experiment h showed little improvement due to seeding and
re-seeding the garbage compost pile, the writer still believes that back
seeding will play an important part in the future composting process.
{Thermophilic organisms do the major job on the decomposition of the waste
material under a definite range of temperature. If an Optimum tenperature
'were kept favorable to thermophilic organisms, seeding should help the
compost to cross the mesophilic stage and shorten the detention.period at
‘the beginning. .Again, when the temperature rises to above 65°-70°C.,
some thermophilic organisms responsible for breaking down the waste will

‘be killed and a temperature drop might result. This indicates that the

57

composting process might then be transferred to another mesophilic stage
which would be much slower than the thermophilic stage for decomposition.
These considerations suggest the following treatment methods:

1. Prevent the thermal death point to the lower temperature thermo-
philic organisms by controlling the temperature so as to remain within
close limits (hSO-6SOC).

2. Re-seed with thermophilic organisms, if the temperature is over
650-7000, in order to keep the high-speed decomposition going on.

Under the first condition, most pathogenic bacteria were killed
because their death point is around 560-6000, and at the same time the
rapid decomposition can be maintained by the activity of thermophilic
organisms. If it is not possible to control the temperature within
those limits, a re-seeding with thermophilic organisms could probably be
of some value to continue another thermophilic stage, after a satisfactory
sterilization, to Speed up the unfinished decomposition.

Fly Nuisance and Odor Problem in Windrow Compostin&

Insects and eelworms can be killed at a relatively low temperature of
52°C.5 Experiments reported here showed that fly larvae escaped from um...
turned piles and created a serious fly nuisance together with a foul odor.
If turning is not possible, a cover with sawdust, straw or sand to the pile
may be good for 'fly control because the initial activity of young larvae was
always observed at the surface of the new built piles.

Regularly turned compost piles resulted in no fly nuisance.
Laboratory Tests.

Any composted organic matter will break down in time but this time

may not be short under all circumstances. Time has a close relation to

economics and it may be stated that "time means money“. Therefore, every
effort should be made to bring the composts to a good end.product as soon
as possible. For this reason tests for judging the compost are most imp
portant. The following tests have been studied in connection with this
thesis:

1. Percentage of color transmittance (PCT).

PCT test is an easy and an accurate test. When using a green filter
an initial garbage compost PCT of 65 to 90 drops to a value near 10 during
the middle composting stage and then rises again to a final value of around
20. As previously mentioned, the instrument used in this test was a
Klett-Summerson.photoelectric colorimeter. This instrument is easily
carried and is not time consuming. Although the use of PCT proved
reasonably satisfactory, much improvement in technique is still necessary.
0f the three tests reported here the PCT test was the most reliable and
useful.

2. Oxidation-Reduction Potential (ORP) .

The ORP test has long been used for control of sewage treatment plants
but has not, to this writer's knowledge, been used as a garbage composting
test. JUdging by results obtained in Experiment 3, ORP seems to be a good
:means for telling the conditions resulting from aeration by turning. ‘Un-
fortunately, the ORP test had to be dropped after Experiment 3 because of
trouble with the instrument. Also, readings were time consuming due to
a long period of instrument drift while making.measurements. Difficulty
'was encountered in establishing a satisfactory procedure.

3. Hydrogen Ion Concentration (pH).

pH still seems to be a good indicator for garbage composting during

'the initial stages. pH rise from about h.8 to 8.0 during the initial stages

and thus indicates the degree of composting. However, the test is not
sensitive during the final stages and is of little value when working

with lime-filtered sewage sludge.

59

60

SECTION IX

Summary and Conclusions

A number of experiments have been reported in connection with this
thesis. Conclusions pertaining to these experiments and other factors
in this thesis are listed below:

1. A windrow composting without turning may cause odor and fly
nuisance. Unturned windrows required several months to compost. If;
no turning is possible, it is better to use coarser material and the .-
piles should be located some distance from habited areas. An insecticide
must be used continuously during warm weather for at least twenty days
to kill the larvae and flies, since such piles tend to become infested
with larvae.

2. Turning the pile every third day finishes the composting pile
within eighteen days without nuisance. Under the same environmental
conditions if the piles are turned every second day and every day, fourteen

days and nine days reapectively are required for completion.

61

SECTION X

Bibliography

McGauhey, P. H., and Gatass, H. B., "Stabilization of Municipal
Refuse by Composting." Proceedings Vol. 79, A.S.C.E., Oct. 1953.

Snell, John R., "The Future of Composting,“ unpublished report,
April 22, 195k.

Snell, John R. , "High-Rate Composting - A New Idea in Muncipal
Garbage Disposal." The Consulting Engineer's Professional

Magazine , August 1951+ .

"Reclamation of Municipal Refuse by Composting“, Technical
Bulletin No. 9, Series 37, June, 1953, Sanitary Engineering
Research Projects, University of California.

"New Zealand Engineering“, Vol. 6, Nos. 11-12 (Nov.-—Dec., 1951).

Glasstone, S. , “Textbook of Physical Chemistry", 2nd Edition,
April 1946.

"Klett-Summerson Photoelectric Colorimeter", Klett Manufacturing
Co. , New York.

Willard, H. H., Merritt, L.L., and Dean, J.A., "Instrumental
Methods of Analysis”, 2nd Edition, March 1951.

Leininger, E., and Hone, K. G., ”Elementary Analysis, A Practical
Approach“, 2nd.Edition, 1950, Mrs.c. Press.

62

SECTION XI

APPENDIX
(A) Procedure for Obtaining Per Cent Transmittance*

I. 'Preparation of Sample - (This procedure open to further experimentation).

l. Weigh out 10 grams of sample.

2. Place this in 100 cc. water.

3. Shake by hand in an erlyenmyer flask 25 times.

h. Filter.

5. Place 10 cc. in a colorimeter tube and read, using a colorimeter.
II. Procedure for Using Colorimeter.

1. Set colorimeter to zero before turning on. This must be done
before turning on the colorimeter. This is done by turning the pointer
setting knob on top of the instrument until the pointer coincides with the
line on the blank pointer scale.

2. Plug in electric cord outlet.

3. Turn on short circuit switch located at side of instrument.

A. Place a clean colorimeter tube containing distilled water in
the instrument.

5. Turn the scale by means of the large knob on the front of the
instrument until the scale reading is O.

6. Switch on the colorimeter lamp by means of the lamp switch located
on the front of the lamp housing.

7. Switching the lamp on will in general cause the pointer to move

somewhat away from the line on the pointer scale. Turn the zero adjustment

*This procedure was prepared bv-Rnhsrr Tina o+ u c n

63

knob, which is located on the top of the colorimeter to the left Of the
test tube, one way or another until the pointer is brought back to the
line on the pointer scale.

8. Allow the lamp to burn for a few minutes to permit the instrument
to reach equilibrium. Again check the poisition Of the pointer to be sure
that it is on the line. If it is not, turn the zero adjustment know care-
fully until the pointer is exactly on the line. The instrument is now
ready for use.

9. TO read an unknown solution remove the distilled water tube and
place the colorimeter tube containing the unknown solution in the instrument.
The pointer will be deflected from its poSition at the zero line. Turn the
scale now until the pointer has been brought back exactly to the zero line.
The reading on the scale at this point is the reading Of the unknown
solution.

10. Take readings using no filter, a red filter, a green filter
and a blue filter on each sample.

11. The colorimeter scale is graduated in units proportional to the
optical density. The actual numerical values represent the Optical density
divided by two, with the decimal point omitted. A.scale reading of 250
corresponds to an optical density of 0.500. The formula relating scale

reading and Optical density is as follows:

2

where D is density and R is the reading.

It is usually desirable to report the scale readings in terms of

per cent transmittance. TO convert the scale readings to per cent trans-

 

inittance refer to the conversion table in back of the colorimeter handbook.

61:.

It is possible to calculate the per cent transmittance from the
scale reading. This is done as follows:

(a) Obtain the optical density by multiplying the scale

reading'by'0.002.
(b) Subtract the optical density value from 2.000. The result

is the logarithm of the per cent transmittance. From logarithm tables,

obtain the value of the per cent transmittance.

65

(B) Procedure for pH Measurements in Composting
Investigations Using a Beckman H-2, M.S.C.*

I. General Procedure.

(a) Set switch on start. Connect power cord. During five-minute
wait verify meter needle adjustment at 7.00.

(b) Standardize the meter by immersing electrodes in a standard
buffer solution and switching to proper range. Adjust standardization
needle until meter needle indicates exact buffer pH. Switch to neutral
position and.move pointer to mark needle position.

(c) When handling electrodes after start always keep switch
in neutral position.

(d) Always rinse and wipe electrodes before measurements and
set temperature dial at electrode temperature.

II. Measurement of pH.

Switch to neutral and readjust standardization control so needle
rests at pointer position. Immerse electrodes in sample. Switch to
proper range and read pH. Repeat buffer standardization occasionally
during an extended series of measurements.

III. Preparation of sample.

If sample is a liquid no further treatment will be necessary.

If sample is a solid such as compost, place an amount Of sample with
an equal.amount of distilled water (by volume). Stir, immerse electrodes,
and take reading. After sampling, composting material may be kept in a

tightly stoppered container for not more than 3 hours before a.pH determin-

ation is made.

* This procedure was prepared by Robert Lipe at Ms S. C.

(C) Procedure for Moisture and.Ash Determinations
from Samples of Composting.Material, M.S.C.*

In general, the same sample (in the same evaporating dish) shall be
used for both.moisture and ash determinations. After sampling, the material
for these determinations may be kept in a tightly stoppered container for
not more than six hours before the initial weight determination (for moisture
content) is made. The procedures below apply only to material which has been
ground before sampling.

Moisture: Remove from.the sample all visible metal and all particles
having any dimension greater than about one-half inch. However, if particles
of any one type of material with greater dimensions than one-half inch (e.g.,
corn husks or grass) are present in amounts exceeding about ten per cent of
the sample, retain these particles. Place at least 100 gm. (wet weight) Of
the sample thus sorted into a suitably marked porcelain evaporating dish Of
a known weight. Do not place any material higher than one-half inch below
the top of the dish. DO not pack the sample into the dish. Weigh the dish

of wet material immediately on a scale or balance accurate to 0.1 gm.; then

 

place the dish into an electric oven held at a temperature not varying
beyond the limits of 102° to 10k0 c. (or in 85° c sand bath for one hour follow-
ed by a 102° - thOC. oven). Dry the sample for at least twenty-four hours
and re-weigh to 0.1 gm. IMoisture content is expressed in terms of a percentage
of the original (wet) weight of the sample.

If material with an estimated moisture content greater than fifty per

cent is placed in an evaporating dish to a depth of one inch or more, at

* This procedure was prepared by G. F. Mallison at M.S.C.

67

least forty-eight hours drying in a 102°— tho C oven shall be necessary
before determining the dry weight of the sample.

In the M. S. C. sanitary engineering laboratory, all wet samples
shall be dried in a 850 C sand bath for one hour before these samples
are introduced into a 102°— th°C oven.

Agh: When the procedure above has been completed, place the dry
weighed sample in an electric muffle furnace heated to a low red heat
(650°to 700°C). After at least 3 hours in the furnace, remove the
sample and weigh again to 0.1 gm. Ash content is based on the dry weight
of the sample.

Footnote: If the original (wet) weight of a sample is less than
100 gm., all weight determinations for ash and moisture contents shall
be made to 0.01 gm. on an analytical balance. Desiccator cooling of
ashed or oven dried samples shall be necessary before weighing on an

analytical balance.

Wt. of wet sample - wt. Of dry sample X 100
Wt. of wet sample

Computations: $1Moisture

 

1. Ash : Wt. of ash x 100
Wt. of dry sample

'*This procedure was prepared by Gt F. Mallison at M.S.C.

(D) Technique - Oxidation-Reduction Potential*

 

The technique found to be most satisfactory in this laboratory for
the measurement of Redux potential is as follows:
1. Set up a standard laboratory Beckman.pH meter as follows:

(a) Remove 60th electrodes by removing lead lines from
the back of the meter.

(b) Connect a Beckman No. 8970-13 High Temperature Reference
Electrode in place of the standard Reference electrode. In order
to do this it is necessary to use the Beckman Terminal Connector
#700 which adapts pin-type terminals, such as those on.metallic
electrodes to the glass electrode jacket.

(c) In place of the general purpose glass electrode connect
a special one sq. in. platinum.electrode. Because of its large
surface area this type of electrode was found to be much more
satisfactory than one with a smaller surface area.

II. The OxidationeReduction Potential readings (in.MEV) are
taken as follows:

(a) Place the large platinum electrode in a large beaker.
Care should be taken that the electrode does not touch the sides
or bottom of the beaker.

(b) Place sample in the beaker so that entire electrode is
covered by sample. This method was found to be more satisfactory
than forcing the electrode down into the sample.

(c) Turn the control switch to the proper range in.mev and

take reading. This reading should be sub. from.plus-255 which is

*This procedure was nrsnnrsd hv Pnhprt Lina at M'Q n

69

the potential at room temperature of the reference electrode.
(d) If the platinum electrode is connected to the

terminal connector the reading will be positive. If the

reference electrode is connected to the terminal connector

the reading will be negative.

MICHIGAN STRTE UNIV. LIBRARIES

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