aerobic composting. presentation 7: the composting toolkit funded by the indiana department of...

Aerobic CompostingAerobic Composting

Presentation 7:Presentation 7:The Composting ToolkitThe Composting Toolkit

Funded by the Indiana Funded by the Indiana Department of Department of Environmental Environmental Management Recycling Management Recycling Grants ProgramGrants Program

Developed by the Indiana Developed by the Indiana Rural Community Rural Community Assistance Program - Assistance Program - RCAPRCAP

So Let’s Talk About Composting . . . So Let’s Talk About Composting . . .

CompostCompost

NOUN OR VERB?NOUN OR VERB? BOTH!BOTH! The verb: “Composting” is the process by The verb: “Composting” is the process by

which microorganisms break down waste and which microorganisms break down waste and turn it into a valuable product.turn it into a valuable product.

The noun: This end product is referred to The noun: This end product is referred to simply as “compost.”simply as “compost.”

Types of Composting:Types of Composting:Aerobic or Anaerobic?Aerobic or Anaerobic?

We are talking is We are talking is AEROBICAEROBIC composting. composting. That is, composting in the presence of That is, composting in the presence of OXYGEN.OXYGEN. Microorganisms decompose organics aerobically Microorganisms decompose organics aerobically

(with oxygen) under carefully controlled conditions (with oxygen) under carefully controlled conditions to produce finished compost.to produce finished compost.

Anaerobic decomposition is what occurs in a landfill Anaerobic decomposition is what occurs in a landfill with Carbon Dioxide, Methane, and Leachate being with Carbon Dioxide, Methane, and Leachate being three major products.three major products.

Compost HappensCompost Happens


Composting is part science and part art. There Composting is part science and part art. There is no one “correct” recipe for aerobic is no one “correct” recipe for aerobic composting.composting.

You will be introduced in this unit to the You will be introduced in this unit to the basics of aerobic composting and “optimal” basics of aerobic composting and “optimal” conditions, but you need to always keep in conditions, but you need to always keep in mind that flexibility is the key to successful mind that flexibility is the key to successful composting. composting.

Aerobic Composting:Aerobic Composting: Key Components Key Components

AirAir WaterWater Compostable MaterialsCompostable Materials Carbon to Nitrogen RatioCarbon to Nitrogen Ratio Surface AreaSurface Area TemperatureTemperature pHpH Other VariablesOther Variables

Aerobic Composting:Aerobic Composting: Optimal Composting Conditions Optimal Composting Conditions

Oxygen: >5%Oxygen: >5% Moisture Content: 40-60%Moisture Content: 40-60% Carbon to Nitrogen Ratio: 30 to 1Carbon to Nitrogen Ratio: 30 to 1 Shredded Materials Over Chipped Materials Shredded Materials Over Chipped Materials

To Maximize Surface AreaTo Maximize Surface Area Temperature: 90-140 Degrees FTemperature: 90-140 Degrees F pH: 6-8pH: 6-8 Other VariablesOther Variables


Air:Air: Optimal composting Optimal composting

when oxygen is greater when oxygen is greater than 5%than 5%

The air we breath is 21% The air we breath is 21% oxygenoxygen

Right picture is testing Right picture is testing for oxygen level within for oxygen level within the compost pilethe compost pile

Aerobic CompostingAerobic Composting Air:Air:

The microorganisms that perform the composting process require The microorganisms that perform the composting process require oxygen to survive. Because the compost pile provides a plentiful food oxygen to survive. Because the compost pile provides a plentiful food source for these microorganisms they quickly multiply.source for these microorganisms they quickly multiply.

This is beneficial to the composting process, but there can become too This is beneficial to the composting process, but there can become too many microorganisms for oxygen supplies within the pile. Oxygen many microorganisms for oxygen supplies within the pile. Oxygen statically flowing into the pile will be far less than the oxygen being statically flowing into the pile will be far less than the oxygen being consumed by the microorganisms.consumed by the microorganisms.

Thus oxygen levels will begin to fall within the pile from the 21% Thus oxygen levels will begin to fall within the pile from the 21% oxygen level in the surrounding atmosphere. Below 5% oxygen level oxygen level in the surrounding atmosphere. Below 5% oxygen level the microorganisms will begin to be impairedthe microorganisms will begin to be impaired

Regular turning is required of a windrow compost pile restores oxygen Regular turning is required of a windrow compost pile restores oxygen to the compost pile and helps to ensure that oxygen levels do not fall to the compost pile and helps to ensure that oxygen levels do not fall below 5% below 5%


WaterWater An ideal moisture content is between 40-60%.An ideal moisture content is between 40-60%. Composting microorganisms need a wet Composting microorganisms need a wet

environment.environment. >60% is too wet, water will take up too much pore >60% is too wet, water will take up too much pore

space required for proper air diffusion.space required for proper air diffusion. <40% is too dry, decomposition rates will <40% is too dry, decomposition rates will

progressively slow the drier the pile.progressively slow the drier the pile.


Water:Water: Here in Indiana it is unusual to have a pile that is Here in Indiana it is unusual to have a pile that is

too dry, you are more likely to have a pile that is too dry, you are more likely to have a pile that is too wet. A pile that is too wet can be turned on an too wet. A pile that is too wet can be turned on an increased schedule until moisture contents fall increased schedule until moisture contents fall back into desired ranges. back into desired ranges.

In a case where the pile is too dry water may be In a case where the pile is too dry water may be added or the pile may be reshaped to allow more added or the pile may be reshaped to allow more water to enter the pile during the next rainstorm.water to enter the pile during the next rainstorm.


Water:Water: Shaping the compost pile according to moisture Shaping the compost pile according to moisture

content needs is clearly an example of the “art” of content needs is clearly an example of the “art” of compostingcomposting

A concave shape helps to trap water whereas a A concave shape helps to trap water whereas a peak shape helps to shed water.peak shape helps to shed water.


Carbon to Nitrogen RatioCarbon to Nitrogen Ratio Also commonly called the C:N ratio or the brown to green Also commonly called the C:N ratio or the brown to green

ratioratio This is because organics high in carbon tend to be brown (wood This is because organics high in carbon tend to be brown (wood

and old leaves being two examples)and old leaves being two examples) Organics high in nitrogen tend to be green (grass clippings and Organics high in nitrogen tend to be green (grass clippings and

food waste being two examples)food waste being two examples)

An optimal carbon to nitrogen ratio is 30:1An optimal carbon to nitrogen ratio is 30:1 Too much carbon slows the composting processToo much carbon slows the composting process Too much nitrogen “supercharges” the composting process and Too much nitrogen “supercharges” the composting process and

runs the risk of going anaerobic or off-gassing nitrogen compoundsruns the risk of going anaerobic or off-gassing nitrogen compounds—both causing negative odors—both causing negative odors


Common Carbon to Nitrogen Ratios:Common Carbon to Nitrogen Ratios: High Nitrogen Materials:High Nitrogen Materials:

Activated Sewage Sludge: 6:1Activated Sewage Sludge: 6:1 Humus: 10:1Humus: 10:1 Vegetable Food Waste: 15:1Vegetable Food Waste: 15:1 Digested Sewage Sludge: 16:1Digested Sewage Sludge: 16:1 Grass Clippings: 19:1Grass Clippings: 19:1 Cow Manure: 20:1Cow Manure: 20:1 Horse Manure: 25:1Horse Manure: 25:1 Green Leaves: <30:1Green Leaves: <30:1


Common Carbon to Nitrogen Ratios:Common Carbon to Nitrogen Ratios: High Carbon Materials:High Carbon Materials:

Fruit Food Wastes: 35:1Fruit Food Wastes: 35:1 Typical Brown Leaves: 40-80:1Typical Brown Leaves: 40-80:1 Foliage: 40-80:1Foliage: 40-80:1 Corn Stalks: 60:1Corn Stalks: 60:1 Pine Needles: 60-110:1Pine Needles: 60-110:1 Straw: 80:1Straw: 80:1 Bark: 100-130:1Bark: 100-130:1 Paper: 150-200:1Paper: 150-200:1 Wood and Sawdust: 300-700:1Wood and Sawdust: 300-700:1


Steaming compost Steaming compost during turning is a sure during turning is a sure sign that temperatures sign that temperatures are being maintained. are being maintained. An indicator that the An indicator that the oxygen levels, moisture oxygen levels, moisture content, and the C:N content, and the C:N ratio are in balance.ratio are in balance.


Surface Area:Surface Area: Greater surface area accelerates decomposition.Greater surface area accelerates decomposition. There are two primary ways to increase surface There are two primary ways to increase surface

area:area: Smaller particles sizeSmaller particles size Shredding materials over chipping materials Shredding materials over chipping materials


Temperature:Temperature: Exothermic microorganisms decompose waste and Exothermic microorganisms decompose waste and

in the process give off heatin the process give off heat An optimal temperature range is 90-140 degrees FAn optimal temperature range is 90-140 degrees F

Below 90 degrees the composting rate slows Below 90 degrees the composting rate slows substantiallysubstantially

Above 140 degrees the microorganisms have difficulty Above 140 degrees the microorganisms have difficulty functioning and the pile runs the risk of spontaneous functioning and the pile runs the risk of spontaneous combustioncombustion


Temperature:Temperature: A compost pile’s temperature is a balance of the A compost pile’s temperature is a balance of the

heat produced by the respiration of the heat produced by the respiration of the microorganisms offset by the heat lost through microorganisms offset by the heat lost through surface cooling surface cooling

In the winter larger pile sizes may be required to In the winter larger pile sizes may be required to offset heat lossesoffset heat losses

In the summer more frequent turning and smaller In the summer more frequent turning and smaller pile sizes may be required to offset excess heatpile sizes may be required to offset excess heat


TemperatureTemperature One other important function of maintaining high One other important function of maintaining high

temperatures in a compost pile is weed seed temperatures in a compost pile is weed seed destruction and pathogen destruction.destruction and pathogen destruction.

Example: Salmonella destruction requires:Example: Salmonella destruction requires: 20 minutes at 140 degrees F20 minutes at 140 degrees F OrOr 1 hour at 131 degrees F1 hour at 131 degrees F


Temperature: Temperature: Testing temperature within the Testing temperature within the compost pilecompost pile


pHpH Decomposition occurs most efficiently between Decomposition occurs most efficiently between

pH 6 and pH 8.pH 6 and pH 8. During the initial stages of decomposition, organic During the initial stages of decomposition, organic

acids are formed that, under normal conditions, are acids are formed that, under normal conditions, are immediately consumed by microorganisms. immediately consumed by microorganisms. Without enough oxygen in the pile, these acids Without enough oxygen in the pile, these acids will not be converted as quickly.will not be converted as quickly.


Other Variables:Other Variables: There may be other variables of concern as a There may be other variables of concern as a

composting operation is refined to make products composting operation is refined to make products of a specified composition. These variables, which of a specified composition. These variables, which are beyond the scope of this manual, include mass are beyond the scope of this manual, include mass balance, rate of respiration of the microorganisms, balance, rate of respiration of the microorganisms, mixing and agitation of the pile, nutrient balance, mixing and agitation of the pile, nutrient balance, inoculation, wetting agents, cation exchange ratio, inoculation, wetting agents, cation exchange ratio, pathogen destruction, wind velocity, and specific pathogen destruction, wind velocity, and specific elemental composition. elemental composition.

Windrow CompostingWindrow Composting

Most common method of yard waste Most common method of yard waste composting in the United Statescomposting in the United States

Generally a “row” of material is composted, Generally a “row” of material is composted, usually about 10-25 feet wide, 6 feet high, and usually about 10-25 feet wide, 6 feet high, and as long as 150 feet.as long as 150 feet.

Windrow composting has been shown to be Windrow composting has been shown to be highly cost effective. highly cost effective.

WindrowWindrow

Windrow TurnerWindrow Turner

Windrows – Optimum Windrows – Optimum CompositionComposition

Shredded and screened organicsShredded and screened organics Moisture content: 40-60%Moisture content: 40-60% Balanced 30:1 Carbon to Nitrogen ratio Balanced 30:1 Carbon to Nitrogen ratio Frequent turning: Frequent turning keeps the Frequent turning: Frequent turning keeps the

pile aerobic and reduces odorpile aerobic and reduces odor

Volume and Weight ReductionVolume and Weight Reduction

With optimal composting a volume reduction With optimal composting a volume reduction of up to 75% can be achieved and a weight of up to 75% can be achieved and a weight reduction of up to 50% can be achieved.reduction of up to 50% can be achieved.

For high water content materials this volume For high water content materials this volume and weight reduction can be as high as 90%.and weight reduction can be as high as 90%.

Single Biggest Problem: ODORSingle Biggest Problem: ODOR

ReasonsReasons#1 Reason is #1 Reason is Lack of OxygenLack of OxygenAlso . . . Out of balance C:N RatioAlso . . . Out of balance C:N RatioAnd . . . Excessive wetnessAnd . . . Excessive wetness

Odor control is discussed in more depth in the Odor control is discussed in more depth in the “Ongoing Operations” section.“Ongoing Operations” section.

Other ProblemsOther Problems

Pathogens destructionPathogens destruction Litter and contaminants (plastic bags, heavy Litter and contaminants (plastic bags, heavy

metals, pesticides)metals, pesticides) End product qualityEnd product quality

Windrow CompostingWindrow CompostingTrouble ShootingTrouble Shooting

Symptom: Symptom: Pile has a bad odorPile has a bad odor Problem: Not enough oxygenProblem: Not enough oxygen Solution: Turn pile daily until odor is goneSolution: Turn pile daily until odor is gone

Symptom: Symptom: Center of pile is dryCenter of pile is dry Problem: Not enough waterProblem: Not enough water Solution: Moisten material while turning pileSolution: Moisten material while turning pile

Symptom: Symptom: Compost is damp and warmCompost is damp and warm Problem: Pile too small or needs more nitrogenProblem: Pile too small or needs more nitrogen Solution: Collect more material and mix the pile. Solution: Collect more material and mix the pile. If still not heating If still not heating

add more nitrogen rich materials.add more nitrogen rich materials. Symptom: Symptom: The pile will not heat upThe pile will not heat up

Problem: Lack of nitrogenProblem: Lack of nitrogen Solution: Mix in a nitrogen source such as grass clippings, fresh Solution: Mix in a nitrogen source such as grass clippings, fresh

manure, or fertilizermanure, or fertilizer

Windrow Composting - OverallWindrow Composting - Overall

Capital costs Capital costs generally low generally low Operating costs Operating costs generally low generally low Land requirements Land requirements high high Control of Air Control of Air limited unless forced aeration is used limited unless forced aeration is used Operational control Operational control turning frequency, amendment, or turning frequency, amendment, or

compost recycle additioncompost recycle addition Sensitivity to cold or wet weather Sensitivity to cold or wet weather sensitive unless in sensitive unless in

housinghousing Control of odors Control of odors depends on feedstock, potential large- depends on feedstock, potential large-

area sourcearea source Potential operating problems Potential operating problems susceptible to adverse susceptible to adverse

weatherweather

Windrow Composting - ConclusionWindrow Composting - Conclusion

Most commonly used composting technique in Most commonly used composting technique in Indiana and NationallyIndiana and Nationally

Uses aerobic microorganisms to breakdown Uses aerobic microorganisms to breakdown woody, yard waste, and food waste products woody, yard waste, and food waste products into a useful “compost” end productinto a useful “compost” end product

When compared against the capital costs of When compared against the capital costs of other MSW management techniques, it is very other MSW management techniques, it is very cost effectivecost effective

QUESTIONS?QUESTIONS?

Thank You!Thank You!

Additional Questions, Comments, or You Additional Questions, Comments, or You Think You Have A Potential Pilot CommunityThink You Have A Potential Pilot Community Please Feel Free to Contact Me:Please Feel Free to Contact Me:

Mark W. DavisMark W. Davis

Technical Assistance ProviderTechnical Assistance Provider

Rural Community Assistance ProgramRural Community Assistance Program

Office: 1-800-382-9895Office: 1-800-382-9895

Wireless: (812) 320-0720Wireless: (812) 320-0720

E-mail: [email protected]: [email protected]

aerobic composting. presentation 7: the composting toolkit funded by the indiana department of...

Documents

composting microorganisms

composting process

basics of aerobic composting

composting toolkitfunded

types of composting

successful composting

oxygen levels

windrow compost pile