This document provides information on the compost process, including different types of composting methods and the microbial ecology involved. It discusses aerobic composting in detail, outlining the three phases: mesophilic, thermophilic, and curing. Key factors that optimize compost include oxygen supply, particle size and structure, moisture and temperature control, carbon to nitrogen ratio, balance of nutrients, and pH. Industrial composting operations are also described.

1. The Compost ProcessThe Compost Process
is Truly

2. Composting is a managedComposting is a managed
biological process that convertsbiological process that converts
biowastes into useful humus.biowastes into useful humus.

3.  AerobicAerobic
Types of CompostingTypes of Composting
–Aerobic composting requires oxygen. ProperAerobic composting requires oxygen. Proper
aeration is critical for the process to workaeration is critical for the process to work
efficiently, therefore, turning the windrow pile isefficiently, therefore, turning the windrow pile is
essential.essential.
 AnaerobicAnaerobic
–Anaerobic composting requires no oxygen andAnaerobic composting requires no oxygen and
is performed within a closed system. It is also ais performed within a closed system. It is also a
potential source for power or “Bio-fuel”.potential source for power or “Bio-fuel”.

4. Aerobic CompostingAerobic Composting
 Much of the compostMuch of the compost
literature focuses onliterature focuses on
aerobic composting.aerobic composting.
Small and mediumSmall and medium
sized compostingsized composting
operations, and evenoperations, and even
large scale operations,large scale operations,
generally performgenerally perform
aerobic composting.aerobic composting.
This presentation will focus on aerobic composting.

5.  During composting, microorganismsDuring composting, microorganisms
break down organic matter andbreak down organic matter and
produce carbon dioxide, water, heat,produce carbon dioxide, water, heat,
and humus.and humus.
 Humus is vitally important for theHumus is vitally important for the
soil and the vegetation growing in it.soil and the vegetation growing in it.
The Compost Process

6. Benefits of HumusBenefits of Humus
 Reduces soil temperature fluctuations.Reduces soil temperature fluctuations.
 Increases water holding capacity of theIncreases water holding capacity of the
soil.soil.
 Increases nutrient holding capacity of soil.Increases nutrient holding capacity of soil.
 Serves as a nitrogen reservoir for plants.Serves as a nitrogen reservoir for plants.
 Improves soil texture and tilth; promotesImproves soil texture and tilth; promotes
“crumb structure”.“crumb structure”.
 Improves crop quality.Improves crop quality.

7. Substance of HumusSubstance of Humus
 ““Humus is not merely the residue leftHumus is not merely the residue left
when vegetable and animal residueswhen vegetable and animal residues
decay. It contains in addition the valuabledecay. It contains in addition the valuable
materials synthesized and left behind bymaterials synthesized and left behind by
the fungi and bacteria of the soilthe fungi and bacteria of the soil
population.”population.”
 Sir Albert Howard, Compost PioneerSir Albert Howard, Compost Pioneer
Howard, Sir Albert and Yeshwant D. Wad. 1931. The Waste Products of Agriculture Their Utilization as
Humus. Humphrey Milford Oxford University Press. Page 14.

8. Microbial Ecology of CompostMicrobial Ecology of Compost
•Composting is characterized by intense microbial activity.
•Composting has three distinct phases:
•Mesophilic Phase
•Thermophilic Phase
•Curing and Maturation Phase
•Microbial communities are dynamic throughout each phase of the compost
process. The existence of various species or communities is generally driven
by the temperature of the compost and the nutrient availability.
•Compost undergoes a “Self-heating” phenomenon, in which the temperature
of the compost pile increases due to the metabolic activity of microbial
organisms.
•The self heating mechanism exerts a sanitation or “Kill Step” on the soil
community. Virtually all pathogens, weed seeds and mesophilic organisms
are killed during this step.
•Compost provides an excellent example of microbial succession.

9. Mesophilic range
(20-35°C)
Thermophilic range
(36-80 °C)
Mesophilic organismsMesophilic organisms
include:include:
Thermophilic organisms include:Thermophilic organisms include: Curing Phase organisms:Curing Phase organisms:
LactobacillusLactobacillus spp.spp.
BacillusBacillus spp.spp.
ClostridiumClostridium spp.spp.
PseudomonasPseudomonas
putidaputida
EnterobacteriaEnterobacteria
aerogenesaerogenes
Escherichia coliEscherichia coli
I. BacteriaI. Bacteria
 BacillusBacillus
stearothermophilusstearothermophilus
 ThermomonosporaThermomonospora spp.spp.
 ThermoactinomycesThermoactinomyces spp.spp.
 Clostridium thermocellumClostridium thermocellum
II. FungiII. Fungi
 Geotrichum candidumGeotrichum candidum
 Aspergillus fumigatusAspergillus fumigatus
 Mucor pusillusMucor pusillus
 Chaetomium thermophileChaetomium thermophile
 Thermoascus auranticusThermoascus auranticus
 Torula thermophilaTorula thermophila
 ActinomycetesActinomycetes
 FungiFungi
 Return of MesophilicReturn of Mesophilic
organisms that eitherorganisms that either
(a)(a) survived the heatsurvived the heat
process orprocess or
(b)(b) recolonized the pile.recolonized the pile.
Finished CompostFinished Compost
organisms:organisms:
Highly variedHighly varied
 Heterotrophic Plate Count 1 x 10Heterotrophic Plate Count 1 x 101010
CFU/gdwCFU/gdw
 Anaerobic Plate Count Aerobes: Anaerobes at 10:1 or greaterAnaerobic Plate Count Aerobes: Anaerobes at 10:1 or greater
 Yeasts and Molds 1 x 10Yeasts and Molds 1 x 1055
CFU/gdw CFU/gdw
 Actinomycetes 1 x 10Actinomycetes 1 x 1088
CFU/gdwCFU/gdw
 66
Curing Phase
(Ambient 25-40 °C)
Time

10. Industrial CompostingIndustrial Composting
 Composting is an industry; involving heavyComposting is an industry; involving heavy
equipment, organized management, costsequipment, organized management, costs
and labor.and labor.

11. Industrial CompostingIndustrial Composting
 Compost can also be packaged and sold to cover costs.Compost can also be packaged and sold to cover costs.
 Compost operators can collect dumping fees.Compost operators can collect dumping fees.
 Compost is generally not profitable, however it is aCompost is generally not profitable, however it is a
sensible way to divert organic waste into a useful soilsensible way to divert organic waste into a useful soil
enhancer.enhancer.

12. Windrow composting is a typicalWindrow composting is a typical
compost management system forcompost management system for
medium to large facilities.medium to large facilities.
Windrows may be up to 3 meters
wide, 1.5 meters high and up to
100 meters long.

13. Windrow ConstructionWindrow Construction

14. Porous BasePorous Base

15. The FeedstockThe Feedstock
Carbon source: yard waste from south suburban Chicago

16. The FeedstockThe Feedstock
•Leaves are collected from local municipalities.
•Leaves and other yard wastes are a good source
of carbon and a good bulking agent for the compost
pile.

17. The FeedstockThe Feedstock
Nitrogen source: waste from the herb farm

18. Windrow ConstructionWindrow Construction
A windrow is constructed by mechanized equipment.

19. Mixing EquipmentMixing Equipment
 Motorized mixing tines ensure that the nitrogen richMotorized mixing tines ensure that the nitrogen rich
“greens” and the carbon rich “browns” are mixed“greens” and the carbon rich “browns” are mixed
properly.properly.
 The windrow will be turned daily for several weeks,The windrow will be turned daily for several weeks,
and then less frequently with time.and then less frequently with time.

20. Windrow DimensionsWindrow Dimensions
Windrows may be up to 3 meters wide, 1.5 meters high and up to 100
meters long.

21. Insulated CoveringInsulated Covering
A poly fiber material covers the windrow.

22. Insulated CoveringInsulated Covering
The covering helps control moisture by allowing the
compost to “breath”

23. Temperature controlTemperature control
The insulating fabric helps control temperature
modulations.

24. 120-Day Cycle120-Day Cycle
 After approximately aAfter approximately a
120-day cycle, the120-day cycle, the
compost is stable andcompost is stable and
ready for furtherready for further
processing. The finalprocessing. The final
processing ensures aprocessing ensures a
usable and safeusable and safe
product for manyproduct for many
applications.applications.

25. Screening EquipmentScreening Equipment
 Screening equipment removes potential
foreign objects such as rocks, glass or
plastic.
 Screening the compost also helps break up
clumps and improve crumb structure.

26. Transport and storage of compostTransport and storage of compost
 After screening, the compost is conveyed andAfter screening, the compost is conveyed and
stored in large piles.stored in large piles.

27. Soil Enhancer for AgricultureSoil Enhancer for Agriculture
 The compost can then be used as a valuableThe compost can then be used as a valuable
soil amendment for agriculture.soil amendment for agriculture.
 Compost is useful for soil building and erosionCompost is useful for soil building and erosion
control, as well as a good source of mineralscontrol, as well as a good source of minerals
and microorganisms.and microorganisms.

28. SurplusSurplus
Surplus compost can be packaged and sold on the open market
by registered facilities.

29. Main factors for Compost OptimizationMain factors for Compost Optimization
 Oxygen SupplyOxygen Supply
 Particle Size and StructureParticle Size and Structure
 Moisture and Temperature ControlMoisture and Temperature Control
 Carbon : Nitrogen RatioCarbon : Nitrogen Ratio
 Balance of NutrientsBalance of Nutrients
 pHpH

30. Oxygen SupplyOxygen Supply
•A mixing tine attaches to a tractor and thoroughly turns
the compost pile.

31. Oxygen SupplyOxygen Supply
Mixing the pile regularly helps redistribute oxygen,
moisture and heat; keeping the windrow healthy and
aerobic.

32. Particle Size And StructureParticle Size And Structure
•One of the important goals of a successful compost
operation is production of a soil with good “crumb
structure”.
•A properly aerated compost that is in the moisture range
of 50% +/- 5% with a good balance of nutrients will
naturally form a well structured soil.

33. Moisture and Temperature ControlMoisture and Temperature Control
 A water tank behind the mechanical turner allows theA water tank behind the mechanical turner allows the
windrow to be irrigated and cooled.windrow to be irrigated and cooled.
 The green canvas covering the windrow is a speciallyThe green canvas covering the windrow is a specially
designed cover that insulates and allows the windrow todesigned cover that insulates and allows the windrow to
“breathe”.“breathe”.
 Moisture should be monitored using laboratory methodsMoisture should be monitored using laboratory methods
or the “squeeze test” to maintain a moisture level ofor the “squeeze test” to maintain a moisture level of
approximately 45-55%approximately 45-55%

34. Mean Windrow Temperature Profile
(n = 10)
0
10
20
30
40
50
60
70
80
0 10 20 30 40 50 60 70 80 90 100 110
Compost Process Time (Days)
Temperature(C°)
Thermophilic zone

35. Carbon : Nitrogen RatioCarbon : Nitrogen Ratio
 Carbon materials, known as browns, including leaves,Carbon materials, known as browns, including leaves,
straw and ash should represent 95-98% of the totalstraw and ash should represent 95-98% of the total
mass.mass.
 Nitrogenous materials (a.k.a. greens) such as foodNitrogenous materials (a.k.a. greens) such as food
waste, manure and green manure should represent 2-waste, manure and green manure should represent 2-
5% of the total mass.5% of the total mass.

36. 25:1 Carbon / Nitrogen ratio is ideal
Carbon : Nitrogen RatioCarbon : Nitrogen Ratio

37. Balance of NutrientsBalance of Nutrients
 Essential nutrients include carbon, nitrogen,Essential nutrients include carbon, nitrogen,
phosphorus, potassium and other trace mineralsphosphorus, potassium and other trace minerals
such as manganese, boron, cobalt, copper,such as manganese, boron, cobalt, copper,
iodine, iron, molybdenum and zinc.iodine, iron, molybdenum and zinc.

38. pHpH
•A pH range between 5.5 and 8.0 will ensure that a
wide range of microorganisms will thrive in the compost
environment.
•Most compost piles using typical feedstock will
maintain this pH range with no additional input
requirement. In fact, as long as the pile is properly
aerated and the feedstock sources are not known to be
excessively acidic (i.e. pine needles), the pile will tend
to stay within this tight range simply by nature alone.

39. Sanitation of CompostSanitation of Compost
 Properly cured Compost is known as aProperly cured Compost is known as a
stable and hygienic form of naturallystable and hygienic form of naturally
processed soil material.processed soil material.
 Compost has a good record of safety inCompost has a good record of safety in
regards to pathogens, weed seeds and flyregards to pathogens, weed seeds and fly
larvae.larvae.

40. Thermophilic TemperaturesThermophilic Temperatures
 High Temperatures generated in compostHigh Temperatures generated in compost
windrows “sanitize” the raw compost,windrows “sanitize” the raw compost,
altering the compost material physically,altering the compost material physically,
chemically and microbiologically.chemically and microbiologically.
 Temperatures in the range of 55°- 75° CTemperatures in the range of 55°- 75° C
for a period of three days is a standardfor a period of three days is a standard
rule-of-thumb for sanitation of compost.rule-of-thumb for sanitation of compost.

41. Overall monitoring strategy.
 Ten windrow piles at a landscape waste composting facilityTen windrow piles at a landscape waste composting facility
located on converted agricultural land in northern Illinoislocated on converted agricultural land in northern Illinois
measuring approximately 6.6 hectares in area were the studymeasuring approximately 6.6 hectares in area were the study
area for this experiment.area for this experiment.
 The sampling period was a 120-day duration during the springThe sampling period was a 120-day duration during the spring
and summer of the year 2007.and summer of the year 2007.
 The ten windrows were tested approximately daily forThe ten windrows were tested approximately daily for
temperature and oxygen content, and weekly for the following:temperature and oxygen content, and weekly for the following:
 moisture contentmoisture content
 pHpH
 water activitywater activity
 microbial indicators including:microbial indicators including:
 total plate count (TPC)total plate count (TPC)
 ColiformColiform
 Yeast PopulationsYeast Populations
 Mold populations.Mold populations.

42. Materials and MethodsMaterials and Methods
 Equipment needed to SampleEquipment needed to Sample
Compost:Compost:
 Long-Handled spading shovelLong-Handled spading shovel
 Container in which suContainer in which subb--samplessamples are mixed:are mixed:
a 20-liter plastic pail isa 20-liter plastic pail is idealideal
 4-liter Ziplock plastic bags4-liter Ziplock plastic bags
 Sharpie marker to identify bagsSharpie marker to identify bags
 Small cooler and gel-ice-paks (no ice)Small cooler and gel-ice-paks (no ice)
 Stainless steel thermometer with digitalStainless steel thermometer with digital
gaugegauge

43. MATERIALS & METHODSMATERIALS & METHODS
 Samples were taken inSamples were taken in
the following manner:the following manner:
 Windrows were turned onWindrows were turned on
the same day asthe same day as
sampling, prior tosampling, prior to
sampling, to ensure asampling, to ensure a
homogenous composthomogenous compost
mixture.mixture.
 At each sample location,At each sample location,
five evenly spaced pointsfive evenly spaced points
(sub-samples), 30 cm(sub-samples), 30 cm
apart were selected onapart were selected on
each side of the windrow.each side of the windrow.
1
2
3
4
5
6
7
8
9
10
Sub-samples

44.  Approximately one literApproximately one liter
of compost material fromof compost material from
each of the ten sub-each of the ten sub-
sample sites wassample sites was
removed with a sanitizedremoved with a sanitized
spade shovel and placedspade shovel and placed
into a clean and dry 20into a clean and dry 20
liter plastic bucket.liter plastic bucket.
 Approx. 2.5 kg of wellApprox. 2.5 kg of well
mixed soil material wasmixed soil material was
placed into a 4-literplaced into a 4-liter
plastic sample bag andplastic sample bag and
stored in the cooler withstored in the cooler with
frozen gel packs.frozen gel packs.
MATERIALS & METHODSMATERIALS & METHODS

45.  The samples were processed in a professionalThe samples were processed in a professional
food and environmental microbiology laboratory.food and environmental microbiology laboratory.
MATERIALS & METHODSMATERIALS & METHODS

46.  Microbiological testingMicrobiological testing
was performed usingwas performed using
3M Petrifilm3M Petrifilm®®
::
 Total Plate Count (TPC)Total Plate Count (TPC)
 Coliform / E. coliColiform / E. coli
 Yeast and Mold (YM)Yeast and Mold (YM)
MATERIALS & METHODSMATERIALS & METHODS

47. • Pure Water source: The Millipore Milli-Q
system produces lab grade, pure water for
microbial analysis.
Equipment used for lab procedures:Equipment used for lab procedures:

48. Equipment used for lab procedures:Equipment used for lab procedures:
• 3M Pipettor and poly pipettes3M Pipettor and poly pipettes

49. Equipment used for lab procedures:Equipment used for lab procedures:
 Sterile Whirlpak bags (250ml capacity)Sterile Whirlpak bags (250ml capacity)

50. Equipment used for lab procedures:Equipment used for lab procedures:
 Lab Grade Scale for weighing samples.Lab Grade Scale for weighing samples.

51. Equipment used for lab procedures:Equipment used for lab procedures:
 Incubator set at 35° C for Coliform and TPCIncubator set at 35° C for Coliform and TPC
plates.plates.
 Incubator set at 20° C for Yeast and Mold plates.Incubator set at 20° C for Yeast and Mold plates.

52.  A vacuum oven for moisture testing set at 70° C.A vacuum oven for moisture testing set at 70° C.
 The compost samples were dried for 12 hoursThe compost samples were dried for 12 hours
under vacuum to assure complete mineralization ofunder vacuum to assure complete mineralization of
the soil.the soil.
Equipment used for lab procedures:Equipment used for lab procedures:

53. Lab HygieneLab Hygiene
 Lab hygiene is an important control point to prevent contamination during testing.Lab hygiene is an important control point to prevent contamination during testing.
 Handwash and surface sanitation was achieved with chemical sanitizers and wipes.Handwash and surface sanitation was achieved with chemical sanitizers and wipes.

54. Serial DilutionsSerial Dilutions
Serial dilutions of the compost samples were performed using
standard protocol such as those described in Pepper, Gerba and
Brendecke, 1995. Environmental Microbiology A Laboratory
Manual. Academic Press, Inc. pp 91-94

55. Serial DilutionsSerial Dilutions
The purpose of serial dilutions is to determine the countable
range for the samples being tested and for ease of counting.

56. Inoculating the Petrifilm PlateInoculating the Petrifilm Plate
Using a sterile pipettor tip, 1 mL of aliquot was
transferred directly onto the exposed surface of
the petrifilm plate.

57. IncubationIncubation
The plates were incubated at 35° C for 48 hours.
After incubation, the plates were counted and
recorded onto a log sheet.

58. Counting coloniesCounting colonies
Clean Plate
Plate with coliform
colonies growing
Classic coliform appearance:
red colony with gas forming

59. Compost and HygieneCompost and Hygiene
 This research suggests that the aerobicThis research suggests that the aerobic
compost process effectively reduces orcompost process effectively reduces or
eliminates coliforms and other indicatoreliminates coliforms and other indicator
organisms.organisms.
 Future research should investigateFuture research should investigate
sources of post-process coliformsources of post-process coliform
contamination such as equipment, watercontamination such as equipment, water
sources or environmental contamination.sources or environmental contamination.