The Art andThe Art andThe Art andThe Art andThe Art andScience of CompostingScience of CompostingScience of CompostingScience of CompostingScience of CompostingA resource for farmers and compost producers

Leslie CooperbandLeslie CooperbandLeslie CooperbandLeslie CooperbandLeslie CooperbandUniversity of WUniversity of WUniversity of WUniversity of WUniversity of Wisconsin-Madisonisconsin-Madisonisconsin-Madisonisconsin-Madisonisconsin-Madison

Center for Integrated Agricultural SystemsMarch 29, 2002

Table of Contents

The Composting Process 1

Setting Up the Composting Environment 3

Determining Compost Mixes 5

General Guidelines for Pile Management 5

Managing Foul Odors 6

Siting Considerations, Technology Options and Management Intensity Levels 6

Siting Considerations 6

Composting Technologies 7

Choosing a Composting Method 8

Composting Regulations and Permits 11

Qualities of the Finished Compost 11

Compost Quality Standards 11

Summary 12

Resources 13

The Composting Process

Organic Matter

Minerals

Water

Micro-organisms

Organic matter, minerals, water, microbes

Raw Materials Finished compostO2

Water Heat

CO2

Compost Pile

Figure 1. The Composting Process. Figure 1. The Composting Process. Figure 1. The Composting Process. Figure 1. The Composting Process. Figure 1. The Composting Process. Adapted from Rynk,1992.

What is composting?What is composting?What is composting?What is composting?What is composting?Composting is controlled decomposition, the naturalbreakdown process of organic residues. Compostingtransforms raw organic waste materials into biologicallystable, humic substances that make excellent soilamendments. Compost is easier to handle than manureand other raw organic materials, stores well and isodor-free.

Composting is an ancient technology, practiced todayat every scale from the backyard compost pile to largecommercial operations. There are Roman and biblicalreferences to composting. The nation’s first president,George Washington, was also the nation’s firstrecognized composter. Washington recognized thedegradative effects of farming on soil and he built a“dung repository” to make compost from the animalmanures so he could replenish the soil’s organic matter.

Uses and markets for compostAs landfills reach their capacity and ban acceptance oforganic wastes, composting is an increasingly viablemeans of organic waste management. Compostinganimal manures can also be a solution to manuremanagement on the farm. Most importantly, the finalproduct is a valuable soil resource. Compost canreplace materials like peat and topsoil as seed starters,container mixes, soil amendments, mulches and naturalfertilizers in commercial greenhouse production, farms,landscaping, turf and land remediation (Table 1).

There is a big potential demand for compost in plantproduction-related industries—close to 900 millioncubic yards of compost could be used in agricultural

and horticultural applications and 0.6 million cubicyards for land fill covers and surface mine remediation(U.S. EPA, 1998).

Benefits of adding compost to soilsCompost is an organic matter source with a uniqueability to improve the chemical, physical, and biologicalcharacteristics of soils. It improves water retention insandy soils and promotes soil structure in clayey soilsby increasing the stability of soil aggregates. Addingcompost to soil increases soil fertility and cationexchange capacity and can reduce fertilizerrequirements up to 50%. Soil becomes microbiallyactive and more suppressive to soil-borne and foliarpathogens. Enhanced microbial activity also acceleratesthe breakdown of pesticides and other syntheticorganic compounds. Compost amendments reduce thebioavailability of heavy metals—an important quality inthe remediation of contaminated soils.

The Composting ProcessThe Composting ProcessThe Composting ProcessThe Composting ProcessThe Composting ProcessComposting occurs through the activity ofmicroorganisms naturally found in soils. Under naturalconditions, earthworms, nematodes and soil insectssuch as mites, sowbugs, springtails, ants, and beetles domost of the initial mechanical breakdown of organicmaterials into smaller particles. Under controlled

conditions, composters break down large particlesthrough grinding or chopping. Once optimal physicalconditions are established, soil bacteria, fungi,actinomycetes and protozoa colonize the organicmaterial and initiate the composting process (Figure

TTTTTable 1. Compost Markets and Useable 1. Compost Markets and Useable 1. Compost Markets and Useable 1. Compost Markets and Useable 1. Compost Markets and Use

MarketMarketMarketMarketMarket Compost UseCompost UseCompost UseCompost UseCompost UseAgronomic Soil amendment

Horticultural Seed starter, soil amendment,mulch, container mix,natural fertilizer

Urban/suburban Soil amendment, mulchlandscaping

Turf Seed starter, soil amendment,topsoil, natural fertilizer, mulch

Forestry Seed starter, soil amendment,topsoil, mulch

Land reclamation Soil amendment, mulchBioremediationLand fill cover

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Figure 2. TFigure 2. TFigure 2. TFigure 2. TFigure 2. Temperature changes in an average compostemperature changes in an average compostemperature changes in an average compostemperature changes in an average compostemperature changes in an average compostpile.pile.pile.pile.pile.

Figure 3. Steaming compost pile during active,Figure 3. Steaming compost pile during active,Figure 3. Steaming compost pile during active,Figure 3. Steaming compost pile during active,Figure 3. Steaming compost pile during active,thermophilic phase of composting, when compostthermophilic phase of composting, when compostthermophilic phase of composting, when compostthermophilic phase of composting, when compostthermophilic phase of composting, when composttemperatures can reach as high as 150temperatures can reach as high as 150temperatures can reach as high as 150temperatures can reach as high as 150temperatures can reach as high as 150o o o o o FFFFF

1.) These mesophilic organisms function best at warmtemperatures (50-113oF).

The active phase of compostingAs temperatures in the compost pile increase,thermophiles (microorganisms that function attemperatures above 113oF) take over. The temperaturein the compost pile typically increases rapidly to 130-150 oF within 24-72 hours of pile formation, which ismaintained for several weeks. This is called the activephase of composting (Figure 2, 3).

In the active “thermophilic” phase, temperatures arehigh enough to kill pathogens and weed seeds and tobreak down phytotoxic compounds (organiccompounds toxic to plants). Common pathogens killedin this phase are Escherichia coli, Staphylococcus aureus,Bacillus subtillus, and Clostridium botulinum. During thisphase, oxygen must be replenished through passive orforced aeration, or turning the compost pile.

The curing phaseAs the active composting phase subsides, temperaturesgradually decline to around 100oF. The mesophilicmicroorganisms recolonize the pile, and the compost

enters the curing phase. The rate of oxygen consumptiondeclines to the point where compost can be stockpiledwithout turning. During curing, organic materialscontinue to decompose and are converted tobiologically stable humic substances—the mature orfinished compost. Curing is a critical and oftenneglected stage of composting. A long curing phase isneeded if the compost is unfinished or immature. Thiscan happen if the pile has received too little oxygen ortoo little or too much moisture. Immature compostscan contain high levels of organic acids, high C:Nratios, extreme pH values or high salt contents, all ofwhich can damage or kill plants if the compost is

amended to container mixes or the soil.

There is no clearly defined time for curing. Commonpractices in commercial composting operations rangefrom one to four months. Homeowner compost pilescan cure for as long as six to twelve months.

When is the compost finished?There is no fixed time to produce finished compost.Duration depends on feedstocks, composting methodused and management. It can take as little as threemonths and as long as two years. Compost isconsidered finished when the raw feedstocks are nolonger actively decomposing and are biologically andchemically stable. Some practitioners refer to finishedcompost as stable; refering to the state of biologicalactivity. Maturity is usually defined as the degree ofhumification (conversion of organic compounds tohumic substances, which are most resistant tomicrobial breakdown). It is easier to measure compoststability than maturity, so most composters measuretemperature or compost respiration (oxygenconsumption). When the temperature at the center ofthe pile returns to near-ambient levels and oxygenconcentrations in the middle of the pile remain greaterthan 10-15% for several days, compost is consideredstable or finished. These measurements should betaken when the compost pile has at least 50% moisturecontent by weight.

It is important to learn how to assess the maturity orstability of the compost because stability will affectmany of the chemical and biological properties of thecompost, and ultimately how the compost can be used.“Stability indices” and maturity/stability testing areavailable from compost research and educationorganizations (see Resources). Immature orbiologically unstable composts can be used on farms as

A B C DA B C D50

70

90

100

120140

160

Temperature

o F

Time

A=mesophilicB=thermophilicC=mesophilic D-maturation

Active Phase Curing Phase

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a soil amendment ONLY IF applied several monthsprior to planting. Immature composts can also be usedin site remediation, and as land fill covers.

Setting Up the Composting EnvironmentSetting Up the Composting EnvironmentSetting Up the Composting EnvironmentSetting Up the Composting EnvironmentSetting Up the Composting EnvironmentSince composting is a microbial process, providing theright environment for microbes is crucial for successfulcomposting. In other words, feed the microbes and letthem do the work for you! Three factors interact in the

making of good compost:• the chemical makeup of the raw organic ingredients, called feedstocks• the physical size and shape of the feedstocks (porosity of the pile)• the population of organisms involved in the composting process.

Aerobic vs. anaerobic compostingCompost “happens” either aerobically (with oxygen) oranaerobically (without oxygen) when organic materialsare mixed and piled together. Aerobic composting isthe most efficient form of decomposition, andproduces finished compost in the shortest time. If theproper amounts of food (carbon), nutrients, water andair are provided, aerobic organisms will dominate thecompost pile and decompose the raw organic materialsmost efficiently. Pile “heat” is a by-product ofbiological “burning”—the aerobic oxidation of organicmatter to carbon dioxide so that microbes can generateenergy. Optimal conditions for rapid, aerobic

composting are listed in Table 2.

Feedstocks: the quality of the microbial “food”Composts can be made from most organic by-products. Common feedstocks are poultry, hog andcattle manures, food processing wastes, sewage sludge,municipal leaves, brush and grass clippings, sawdust,and other by-products of wood processing.

Ideally, several raw materials should be mixed togetherto create the “ideal” range of conditions listed in Table2. However, in the real world this can’t always happen.Fortunately composting is a forgiving process that canoccur over a wide range of conditions, and if you mixmaterials with an eye to an acceptable moisture contentand carbon-to-nitrogen ratio (Table 3), you can produceacceptable compost with good management practices.In general, the combination of feedstock quality andcompost management will determine the quality ofthe finished product.

The supply of carbon (C) relative to nitrogen (N) is animportant quality of compost feedstocks. It isdesignated as the C:N ratio. The ideal starting range isC:N 25:1 to 35:1. As a general rule, if the C:N ratio isgreater than 20:1, microbes will use all the N for theirown metabolic needs. If the C:N ratio is lower than20:1, they have surplus N and it can be lost to theatmosphere as ammonia gas and cause odor problems.

TTTTTable 3. Common feedstocks and their characteristicsable 3. Common feedstocks and their characteristicsable 3. Common feedstocks and their characteristicsable 3. Common feedstocks and their characteristicsable 3. Common feedstocks and their characteristics(Adapted from Rynk, 1992, and other sources to illustraterepresentative values)

FeedstockFeedstockFeedstockFeedstockFeedstock Moisture contentMoisture contentMoisture contentMoisture contentMoisture content C:NC:NC:NC:NC:N Bulk DensityBulk DensityBulk DensityBulk DensityBulk Density

High in CarbonHigh in CarbonHigh in CarbonHigh in CarbonHigh in CarbonHay 8-10 15-30 -Corn stalks 12 60-70 32Straw 5-20 40-150 50-400Corn silage 65-68 40 -Fall leaves - 30-80 100-300Sawdust 20-60 200-700 350-450Brush, wood chips - 100-500 -Bark (paper mill waste)- 100-130 -Newspaper 3-8 400-800 200-250Cardboard 8 500 250Mixed paper - 150-200 -High in NitrogenHigh in NitrogenHigh in NitrogenHigh in NitrogenHigh in NitrogenDairy manure 80 5-25 1400Poultry manure 20-40 5-15 1500Hog manure 65-80 10-20 -Cull potatoes 70-80 18 1500Vegetable wastes - 10-20 -Coffee grounds - 20 -Grass clippings - 15-25 -Sewage sludge - 9-25 -

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TTTTTable 2. Optimal conditions for rapid, aerobicable 2. Optimal conditions for rapid, aerobicable 2. Optimal conditions for rapid, aerobicable 2. Optimal conditions for rapid, aerobicable 2. Optimal conditions for rapid, aerobiccomposting (Adapted from Rynk, 1992)composting (Adapted from Rynk, 1992)composting (Adapted from Rynk, 1992)composting (Adapted from Rynk, 1992)composting (Adapted from Rynk, 1992)

ConditionConditionConditionConditionCondition AcceptableAcceptableAcceptableAcceptableAcceptable IdealIdealIdealIdealIdeal

C:N ratios of combined 20:1 to 40:1 25-35:1feedstocks

Moisture content 40-65% 45-60% by weight

Available oxygen >5% >10% or moreconcentration

Feedstock particle size < 1 inch Variable

Bulk density 1000 lbs./cu yd 1000 lbs./cu yd

pH 5.5-9.0 6.5-8.0

Temperature 110-150o F 130-140o F(43-66o C.) (54-60o C)

How to calculate the moisture content ofHow to calculate the moisture content ofHow to calculate the moisture content ofHow to calculate the moisture content ofHow to calculate the moisture content ofcompost or feedstockcompost or feedstockcompost or feedstockcompost or feedstockcompost or feedstock

Materials needed: small container, scale,samples of compost or feedstocks1. Weigh the empty container.2. Add 10 g of the material into the container (this is the wet weight).3. Dry the sample for 24 hours in a 110oC oven.4. Reweigh the sample and subtract the weight of the container. This is the dry weight. Determine the moisture content using the following equation:

Moisture content = 100 X (wet weight ñ dry weight) wet weight

Green materials usually have lower C:N ratios thanwoody materials or dead leaves. Animal wastes are moreN rich than plant wastes (Table 3).

The complexity of the carbon compounds also affectsthe rate at which organic wastes are broken down. The

ease with which compounds degrade generally followsthe order: carbohydrates > hemicellulose > cellulose =chitin > lignin. Fruit and vegetable wastes are easilydegraded because they contain mostly simplecarbohydrates (sugars and starches). In contrast, leaves,stems, nutshells, bark and trees decompose moreslowly because they contain cellulose, hemicelluloseand lignin.

Water RequirementsThe ideal moisture content of the compost pile isbetween 45-60% by weight. This should feel moist tothe touch when you squeeze a handful of blendedfeedstocks. The material should hold together but notexude excess water.

Low moisture content will slow the compostingprocess. Moisture also regulates temperature. Drierpiles tend to heat up and cool down more rapidly thanwetter piles, and excessive dryness makes pilessusceptible to spontaneous combustion. Moisturecontent in excess of 60% means pore spaces in thecompost pile will be filled with water rather than air,leading to anaerobic conditions.

Feedstocks with different moisture contents can beblended to achieve ideal moisture content.

Carbonaceous materials like newspaper, and wood by-products like sawdust can be used as bulking (drying)agents. Chipped brush, wood chips, and bark can beadded to fine particle feedstocks to create large porespaces. If you can't achieve the ideal moisture contentby blending feedstocks alone, you can add water tomaterials as you blend them. Take samples and measure

moisture content by drying and weighing.

A common and effective feedstock combination onfarms is manure (high in N, high in moisture),combined with straw bedding (high in C, low inmoisture). Be sure there is enough straw or other drymaterial in the mixture.

pH and temperatureThe acidity or alkalinity of the organic materials,measured by the pH value, affects the growth ofmicroorganisms. Bacterial decomposers prefer a pHrange 6.0-7.5 while fungal decomposers prefer pHrange 5.5-8.0. If the compost pH exceeds 7.5, gaseouslosses of ammonia are more likely to occur. Certainmaterials such as dairy manure, paper processing

wastes and cement kiln dust can raise pH, while foodprocessing wastes or pine needles can lower pH.

Measure pH at the beginning and end of composting.Send samples to a soil lab for saturated paste pH andEC measurements (electrical conductivity or solublesalts). You can also monitor pH using the soil pH kitsfrom farm and garden catalogs.

Ambient air temperatures affect microbial growth andactivity in the compost pile, and hence the rate atwhich the raw materials decompose. In temperateclimates, composting is fastest in spring, summer andfall months and is likely to come to a complete standstill in winter months. However, if pile size is increasedin winter to 8-12 feet tall and 10-12 feet wide, piles can

Estimating the carbon content of feedstocksEstimating the carbon content of feedstocksEstimating the carbon content of feedstocksEstimating the carbon content of feedstocksEstimating the carbon content of feedstocks

% carbon = %volatile solids1.8

where %volatile solids = 100 - %ash (materialincinerated at 500o C.)

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TTTTTaking the temperature of your compost pileaking the temperature of your compost pileaking the temperature of your compost pileaking the temperature of your compost pileaking the temperature of your compost pile∑ Use a probe with a 3 foot stem.∑ Leave in place long enough for the reading to

stabilize.∑ Take readings in several locations ñ at different

depths from the top and sides.∑ Find the hottest pockets.∑ Graph your findings as in Figure 2.

retain heat and remain active.

Determining compost mixesDetermining compost mixesDetermining compost mixesDetermining compost mixesDetermining compost mixesMany composters determine their feedstock mix bythe look and feel of the mix. With an eye tooptimizing C:N ratio and moisture content, and someexperience with the raw materials, this trial and errorapproach can often work. For composters trying outnew materials, for larger operations, or whencomposting needs to be efficient, more precisecompost recipes can be calculated using formulas andcomputer spreadsheet programs that are based on thecharacteristics of the raw materials (see Resources).

General Guidelines for PileManagement

Managing compost piles for goodManaging compost piles for goodManaging compost piles for goodManaging compost piles for goodManaging compost piles for goodaerationaerationaerationaerationaerationA well-aerated compost pile has at least5% oxygen content during the active phaseof composting (ideally closer to 10%).Composts must be aerated either passivelyor actively as aeration is key to successfulcomposting. As microbial activity increasesin the compost pile, more oxygen will beconsumed. If the oxygen supply is notreplenished, composting can shift toanaerobic decomposition, slowing of thecomposting process and foul odors.

Oxygen monitoring equipment is available,but is expensive. Temperature, odors andmoisture are easy to measure and provide agood indication of active decompositionand adequate aeration. Monitortemperature at least weekly, using athermometer with a three-foot stem and arange from 0 to 200 degrees F. Check themoisture content and odor. A compostpile is not odor-free, but a distinct foulodor usually means anaerobic conditionshave developed. An ammonia smell can mean too

much nitrogen is present, which can be corrected bymixing in carbon-rich materials. A putrid odor canmean too much water—correct by mixing in bulkingmaterials (see Table 3).

Good aeration can also be achieved by managing pileporosity. Porosity is defined as the volume of poresdivided by the total volume of compost. Some ofthose pores will be filled with water and the rest withair. The initial pile mix should have between 45-60%air-filled porosity and during the active phase ofcomposting, it shouldn't drop below 35% (see sidebar:How to measure bulk density and porosity).

Managing Pile MoistureWater will be given off as vapor during the activephase of composting, when temperatures are high. If

you are turning piles, you can add water as you turn.

If you are using static aeration, it is much moredifficult to add water to the compost pile. It is best tomake initial feedstock blends on the wet side (65-70%)by weight, so that when they lose moisture vapor, theywill still be wet enough to keep microbes active. Somecommercial composters using forced aeration systemsadd moisture by introducing humidified air into pipes

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How to measure pile bulk density and air-filled porosityHow to measure pile bulk density and air-filled porosityHow to measure pile bulk density and air-filled porosityHow to measure pile bulk density and air-filled porosityHow to measure pile bulk density and air-filled porosity

First determine bulk density bulk density bulk density bulk density bulk density (the weight per unit volume of your combinedfeedstocks). Weigh the container (5 gallon bucket) empty. Add material 1/3 full, tapthe bucket five times on a flat hard surface, add another 1/3 of material, tap fivetimes again, then fill to top without tapping. Weigh filled bucket and record.Determine bulk density using the calculations below.

Material measured Example1. Weight of bucket with material (lb) 20.52. Weight of empty bucket 2.03. Weight of material (line 1- line 2) 18.54. Bulk density (lbs/cubic yards)Bulk density (lbs/cubic yards)Bulk density (lbs/cubic yards)Bulk density (lbs/cubic yards)Bulk density (lbs/cubic yards)= 740(line 3 X 40).Note: this conversion factor only works for a 5-gallon bucket.

Take the full bucket with material and fill with water. Use the spreadsheetbelow to calculate air-filled porosity (%)air-filled porosity (%)air-filled porosity (%)air-filled porosity (%)air-filled porosity (%).

Material measured Example1. Weight of bucket withmaterial + water (lb) 46.52. Weight of bucket withmaterial (from line 1 in bulk density table) 20.53. Weight of water (line 1- line 2) 264. % air-filled porosity% air-filled porosity% air-filled porosity% air-filled porosity% air-filled porosity = 62% (line 3 X 2.4)

that blow air into the piles.

Pile sizeThe ideal height and width of the piles will depend onthe porosity and moisture content of the raw materials,composting method and your specific equipment(Table 4). For example, a light, dry pile can be stackedhigher than a wet, dense pile, without the risk of

developing anaerobic conditions within the pile. Smallpiles will be able to maintain higher internal oxygenconcentrations than large piles, but large piles willretain the higher temperatures better than small piles.For a pile to heat and stay hot, the minimum sizeshould be one cubic yard.

The particle size of the feedstock will affect porosity,airflow, and the amount of microbial activity. Smallerparticles have more surface area per unit volume and,therefore, microbes have more surface to colonize.However, if particles are too small, porosity will

decrease and airflow within the compost pile will berestricted. A mix of particle sizes creates the mostporous pile (Figure 4).

Managing Foul OdorsGood aeration promotes active aerobicdecomposition. When piles are too wet, too large, notporous enough, or are degrading too quickly, aerobicbacteria can’t get enough oxygen and anaerobicbacteria take over. Sulfur compounds and other by-products of anaerobic respiration form and odorsbuild. Odors can originate from specific incoming orstockpiled feedstocks (such as sewage sludge, liquidmanure or fish by-products) or poorly aeratedcompost piles. Anaerobic respiration, and resultingodors, can also occur in standing pools of wateraround compost windrows and in water retentionponds. You can minimize odors by proper pilemanagement. Once aerobic conditions arereestablished, the bacteria will “eat” the odorouscompounds.

AmmoniaAmmonia odors can form independent of theaeration of the feedstocks or piles. Nitrogen-richfeedstocks usually have low C:N ratios. If N is inexcess, nitrogen is metabolized in a way that gaseousN compounds (ammonia and nitrous oxide) arereleased. To minimize this, set pile C:N well above10:1 (25-35:1 ideal) and try to blend feedstocks tokeep the pile pH below 7.5.

Siting Considerations, TechnologyOptions and Management IntensityLevels

Siting ConsiderationsSiting ConsiderationsSiting ConsiderationsSiting ConsiderationsSiting ConsiderationsIn choosing a site, consider

• Management operations: access to roads and ease of handling materials• Water quality protection: siting is the first step in preventing leaching and run-off into

Composting methodComposting methodComposting methodComposting methodComposting method Height (feet)Height (feet)Height (feet)Height (feet)Height (feet) WWWWWidth (feet)idth (feet)idth (feet)idth (feet)idth (feet)Static Piles 3-6 12PAWS 3-6 10Windrow Composting - Tractor pulled 6-8 10 Self-propelled turner 3-9 9-20 Bucket loader 6-12 10-20Aerated Static Piles 6-12 10-20In-vessel NA NA

TTTTTable 4. Pile size guidelinesable 4. Pile size guidelinesable 4. Pile size guidelinesable 4. Pile size guidelinesable 4. Pile size guidelines

TTTTTo get aerobic bacteria breathing againo get aerobic bacteria breathing againo get aerobic bacteria breathing againo get aerobic bacteria breathing againo get aerobic bacteria breathing again

∑ Mix wet feedstocks with coarse, dry bulkingagents as soon as they come on site.

∑ Create adequate porosity in compost piles byincreasing the number and sizes of pores, suchas adding wood chips.

∑ Build piles to maximize temperature-drivenconvective air flow

Loosely packed, well structured

Loosely packed, uniform particle size

Tightly packed, uniform particle size

Tightly packed, mixed particle sizes

Figure 4. How porosity affects aeration. From TFigure 4. How porosity affects aeration. From TFigure 4. How porosity affects aeration. From TFigure 4. How porosity affects aeration. From TFigure 4. How porosity affects aeration. From T. Richard,. Richard,. Richard,. Richard,. Richard,Cornell WCornell WCornell WCornell WCornell Waste Management Institute.aste Management Institute.aste Management Institute.aste Management Institute.aste Management Institute.

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Figure 5. Although windrow composting uses moreFigure 5. Although windrow composting uses moreFigure 5. Although windrow composting uses moreFigure 5. Although windrow composting uses moreFigure 5. Although windrow composting uses moreland than other methods, it can be put in the fieldland than other methods, it can be put in the fieldland than other methods, it can be put in the fieldland than other methods, it can be put in the fieldland than other methods, it can be put in the fieldwhere the compost is to be appliedwhere the compost is to be appliedwhere the compost is to be appliedwhere the compost is to be appliedwhere the compost is to be applied

surface or groundwater• Neighborhood relations: odor, noise, dust, debris and appearance of your operation

Leaching of nitrates and other soluble nutrients ismost likely to occur during curing phase and compoststorage. Highly permeable soils are most at risk. Try tofind a soil of intermediate permeability. Ideally, the siteshould be several feet above the seasonally high watertable, and several hundred feet away from wells orsurface water. Consider the slope of the site, especiallythe potential for water to run into the compost pilesduring storms or snowmelt. Plant grass buffer strips toslow run-off. Consider providing roofs over some ofthe composting area to divert precipitation and keepstored compost dry.

Site visibility and appearance can go a long way inmaintaining a good perception of your operation. Usesome of your compost to landscape the site, plant andmaintain trees and grassy areas—these will also helpcontrol and filter run-off from the composting site.Choose a site with some consideration of the homesof neighbors and the direction of prevailing windsduring warm weather. Plan grinding and turning forhours during the day in which neighbors are less likelyto be affected by the odors and noise.

Composting TComposting TComposting TComposting TComposting TechnologiesechnologiesechnologiesechnologiesechnologiesThe most common composting technologies ormethods are

• Static piles• windrow composting• passively aerated windrows• forced aeration, static piles• enclosed, or in-vessel, composting• vermicomposting.

Within these methods are ranges of technologyoptions.

Static PilesStatic piles are the simplest form of composting andrequire little management and equipment. Onceestablished, it is very difficult to adjust moisture, andstatic piles tend to go anaerobic in the center. Aerobicconditions can be achieved if the initial pile porosity ishigh (>60%) and there is a high proportion of bulkingmaterials to keep pores open for air exchange. Whilesimple, this method takes the longest to producefinished compost, and the composted material can be

quite heterogeneous.

Windrow CompostingWindrow is the general term for an elongated pile ofstacked raw materials. (Figure 5). Piles need to besmall (3-6’) and porous enough for air to pass throughthem over a long period of time.

A turned windrow is one that is mechanically turnedusing a bucket loader, manure spreader or a windrowturner (Figure 6A,B). Turning the windrow remixesthe materials, allowing all the raw materials to becolonized by microorganisms in the warmer, moreactive internal part of the compost pile. Oxygen isreintroduced, heat, water vapor and gases escape. Themost important part of turning the pile is thereestablishment of porosity and the ability of air to getinto the pile.

Passively aerated windrow system (PAWS)PAWS includes perforated pipes placed at the base ofeach windrow to promote convective airflowthroughout the pile. The key to this system is thoroughpremixing of feedstocks before placing on theperforated pipes. Also, windrows need to be insulatedwith finished compost to ensure thermophilictemperatures reach the outer edges of the windrow(Figure 6C).

Forced Aerated Static PilesForced aerated static piles are similar to PAWS piles,but blowers are installed at the ends of perforatedpipes or air ducts as shown in Figure 7. Air flow canbe adjusted by changing the frequency and duration ofthe blower. Usually, blowers are set to turn on whenthe compost reaches a maximum temperature (e.g.,150oF).

Enclosed CompostingEnclosed, or in-vessel, composting is mainly for thecommercial compost producer who needs more

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environmental control during the composting process.Some large scale composting operations usecompletely enclosed in-vessel equipment to achievemaximum control of temperature, oxygen andmoisture. Some farms have also successfully used thesmaller, less expensive bin equipment. Equipmentranges from a simple enclosed bin, an agitated bin orreactor, to an entire building devoted to composting.

VermicompostingVermicomposting is worm composting; in which redworms transform decaying organic matter into worm

castings. The castings contain high concentrations ofreadily available nutrients for plants. Vermicompostingdoes not achieve the high (thermophilic) temperaturesin windrow and aerated static pile composting becausethe worms can't survive the high temperatures.

However, research has shown that both pathogens andweed seeds can be destroyed in vermicomposting.Vermicomposting is usually done in containers and canbe done indoors and outdoors, allowing year roundcomposting. The two types of worms best suited toworm composting are the red worms: Eisenia foetida(commonly known as red wiggler, brandling, ormanure worm) and Lumbricus rubellus. They are oftenfound in the litter layers of forests, manure piles andbackyard compost heaps. For more information seeResources.

Choosing a composting methodChoosing a composting methodChoosing a composting methodChoosing a composting methodChoosing a composting methodChoose an approach that best suits your reasons formaking compost, the location of the compost site andthe amount of specialized equipment you haveavailable to produce compost (Figure 8). Where youare located is important from environmental impactand potential nuisance perspectives. For example,composters located in rural areas need to beconcerned that composting activities don't adverselyaffect surface and ground waters, but they usually are

Figure 6a. Mixing poultry litter and agriculturalFigure 6a. Mixing poultry litter and agriculturalFigure 6a. Mixing poultry litter and agriculturalFigure 6a. Mixing poultry litter and agriculturalFigure 6a. Mixing poultry litter and agriculturalbyproducts in a feed mixer for passive aerationbyproducts in a feed mixer for passive aerationbyproducts in a feed mixer for passive aerationbyproducts in a feed mixer for passive aerationbyproducts in a feed mixer for passive aerationcompostingcompostingcompostingcompostingcomposting

Figure 6b. Using a tractor-pulled windrow turner to mixFigure 6b. Using a tractor-pulled windrow turner to mixFigure 6b. Using a tractor-pulled windrow turner to mixFigure 6b. Using a tractor-pulled windrow turner to mixFigure 6b. Using a tractor-pulled windrow turner to mixcannery wastes with sawdust and municipal leavescannery wastes with sawdust and municipal leavescannery wastes with sawdust and municipal leavescannery wastes with sawdust and municipal leavescannery wastes with sawdust and municipal leaves

Figure 6c. TFigure 6c. TFigure 6c. TFigure 6c. TFigure 6c. Turning poultry litter using a self-propelledurning poultry litter using a self-propelledurning poultry litter using a self-propelledurning poultry litter using a self-propelledurning poultry litter using a self-propelledwindrow turnerwindrow turnerwindrow turnerwindrow turnerwindrow turner

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Figure 7. Pipes are inserted into static aeratedFigure 7. Pipes are inserted into static aeratedFigure 7. Pipes are inserted into static aeratedFigure 7. Pipes are inserted into static aeratedFigure 7. Pipes are inserted into static aeratedcompost piles.compost piles.compost piles.compost piles.compost piles.

less concerned about neighbor complaints related toodors, noise and dust. Composting sites located inrural-urban and urban areas often are forced to usehigh technology options to minimize nuisancecomplaints.

The decisions about technology options andmanagement intensity can be viewed as a continuum(Figure 8). If you are new to composting and want tomake compost exclusively for your own use, you mightstart out at the low to intermediate scale. Later if youdecide to make a saleable product or expand your site,you might decide that you can justify the costs ofhigher technologies and more intensive management.

“Low technology” compostingLow technology options usually go hand-in-hand withminimal management. Examples include static,passively aerated piles where you would use dry andlarge-particle size feedstocks to give the compost pilesufficient porosity. Use of a bucket loader to turn pilesinfrequently (every two weeks) would also beconsidered a low-technology option for on-farmcomposting. These options make the most sense forindividuals in rural areas making compost largely fortheir own use.

“Intermediate” technology optionsIntermediate technology - moderate managementintensity includes turned windrow composting using

non-specialized equipment. The most commonexample is building and turning piles using a manurespreader. These windrows would likely be turnedonce per week during the active phase of compostingand then monthly during the curing phase. Thepassively aerated windrow system (PAWS) would alsobe considered an intermediate technology optionbecause the composter will need some kind ofequipment to premix feedstocks and will need topurchase perforated pipe for placement underneaththe compost pile. Management of the PAWS system isintensive in the pile establishment phase, but minimalthereafter. Both of these intermediate technologyoptions are suited to rural or rural-urban fringelocations. Composts produced using these methodswould be best suited to internal use, unless thecomposter can demonstrate product consistency overtime.

“High technology” compostingHigh technology options usually include specializedcomposting equipment: tractor-pulled or self-propelled windrow turners, forced aeration systemswith perforated pipes and blowers and enclosed (or in-vessel) systems. These require serious financial andlabor commitments. Use of these technologies arejustified when the composter intends to make asaleable product and when the compost site is locatedeither on the rural-urban boundary or within an urbansetting. Management intensity of these systems is

Decision tree for identifying composting options

Who are you?

Why do you wantto make compost?

Where are youlocated?

Managementintensity/

appropriatetechnology

Farm Municipality Commercialcomposter

On-farmuse

Saleableproduct

Free, giveaway

Saleableproduct

Saleableproduct

Rural Rural-urban

Rural Rural-urban

Rural-urban

Urban Rural-urban

Urban Rural Rural-urban

Urban

LowStatic,passivelyaerated piles

Low-intermediateHave accessto equipment:manurespreader

IntermediateManurespreader,PAWS

Intermediate-highTractor pullledturners, forcedaeration

Low-intermediateBucket loader,manurespreader

HighWindrowturning equip-ment, enclosedfacilities,forced aeration

IntermediateTractor pulledturner, forcedaeration (low-tech)

Figure 8. Choose an approach that best suits your reasons for making compost, the location of theFigure 8. Choose an approach that best suits your reasons for making compost, the location of theFigure 8. Choose an approach that best suits your reasons for making compost, the location of theFigure 8. Choose an approach that best suits your reasons for making compost, the location of theFigure 8. Choose an approach that best suits your reasons for making compost, the location of thecompost site and the amount of specialized equipment you have available to produce compost.compost site and the amount of specialized equipment you have available to produce compost.compost site and the amount of specialized equipment you have available to produce compost.compost site and the amount of specialized equipment you have available to produce compost.compost site and the amount of specialized equipment you have available to produce compost.

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usually high. For turned windrow systems,windrows are usually turned 2-3x/weekduring the active phase of composting(minimum of 1x/week) and then 1-2x/month during curing. For the forced-aeratedand enclosed technologies, you will need tomonitor the equipment to make sure that airflow and moisture are optimized to producethe desired temperature range.

Studies comparing technology-Studies comparing technology-Studies comparing technology-Studies comparing technology-Studies comparing technology-management effects on compostmanagement effects on compostmanagement effects on compostmanagement effects on compostmanagement effects on compostqualityqualityqualityqualityquality.....There are several studies evaluating theeffects of different composting technologies andmanagement intensities on compost “processvariables” (measurements used to assess how theprocess is progressing) and finished compost. LopezReal and Baptista (1996) evaluated three compostingmethods to determine their effects on compostingprocess variables and methane emissions. The methods

included 1) minimal intervention or passively aeratedstacked manure; 2) windrowing or turned mechanicallywith a manure spreader and 3) forced aeration usingperforated pipes and a blower. They evaluated changesin the first 36 days of composting and found thatwindrowing produced the greatest change in totalvolume and volatile solids compared to minimalintervention and forced aeration (Table 5). Methaneemissions from the passively aerated piles were over100 times greater than the windrow turned piles and1000 times greater than the forced aeration piles.Results showed that introducing air mechanicallyspeeds up the composting process and greatly reducesemissions of a greenhouse gas (methane).

Woods End Research Labs in Maine presentedfindings from two manure compost studies using a

range of composting technologies from no turning tohighly specialized self-propelled windrow turners(Brinton, 1998). The evaluated compost piletemperature and oxygen, organic matter and nitrogenloss and operations & maintenance costs. Resultsshowed that use of a turning machine reduced the timeto finished compost by a few weeks compared to no

turning or use of a manure spreader. Whentemperature profiles were compared,intensification of the composting processeither through turning or adding bulkingmaterial to increase porosity decreased the timeto “stable” compost by approximately 20 days.As management intensification increased, sodid loss of organic matter and nitrogen (Table6). However, the costs associated withtechnology and management also increasedwith intensification (Table 7). They concludedthat if the goal for composting is nutrientmanagement and on-farm use of compost,

intensive technologies and management are notnecessary.

Cost ConsiderationsCost ConsiderationsCost ConsiderationsCost ConsiderationsCost ConsiderationsThese can be grouped into six general

categories: 1) business and site development (mostapplicable to larger scale operations or permittedfacilities), 2) feedstock costs, 3) equipment, 4) labor; 5)management (for large facilities) and 6) marketing and/

TTTTTable 6. Table 6. Table 6. Table 6. Table 6. Technology and management effects on total lossesechnology and management effects on total lossesechnology and management effects on total lossesechnology and management effects on total lossesechnology and management effects on total lossesof organic matter and nitrogen during composting.of organic matter and nitrogen during composting.of organic matter and nitrogen during composting.of organic matter and nitrogen during composting.of organic matter and nitrogen during composting.

TTTTTreatmentreatmentreatmentreatmentreatment Organic Matter loss (%)Organic Matter loss (%)Organic Matter loss (%)Organic Matter loss (%)Organic Matter loss (%) TTTTTotal Nitrogen loss (%)otal Nitrogen loss (%)otal Nitrogen loss (%)otal Nitrogen loss (%)otal Nitrogen loss (%)

Cow manure compost at 120 daysCow manure compost at 120 daysCow manure compost at 120 daysCow manure compost at 120 daysCow manure compost at 120 daysNo turn 70 51Bucket loader-turned 78 60Turned 1x/2 weeks 73 53Turned 2x/week 80 64

Poultry manure compost at 150 daysPoultry manure compost at 150 daysPoultry manure compost at 150 daysPoultry manure compost at 150 daysPoultry manure compost at 150 daysNo turn 75 72Bucket loader-turned 79 76Turned 1x/2 weeks 79 78Turned 2x/week 88 86Source: Brinton, 1998

TTTTTable 5. Percent change in compost total volume and volatile solidsable 5. Percent change in compost total volume and volatile solidsable 5. Percent change in compost total volume and volatile solidsable 5. Percent change in compost total volume and volatile solidsable 5. Percent change in compost total volume and volatile solidsfor three manure composting methods over a 36 day period.for three manure composting methods over a 36 day period.for three manure composting methods over a 36 day period.for three manure composting methods over a 36 day period.for three manure composting methods over a 36 day period.AAAAAverage methane emissions over the same period.verage methane emissions over the same period.verage methane emissions over the same period.verage methane emissions over the same period.verage methane emissions over the same period.

Process variableProcess variableProcess variableProcess variableProcess variable Minimal interventionMinimal interventionMinimal interventionMinimal interventionMinimal intervention WWWWWindrowindrowindrowindrowindrow Forced AerationForced AerationForced AerationForced AerationForced Aeration % change over time

Volume reduction 55 73 55Volatile solids 12 22 15Average methaneemission (ppmv) 28,744 223 3 ppmv = parts per million per volume

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TTTTTable 7. Costs associated with varying technologyable 7. Costs associated with varying technologyable 7. Costs associated with varying technologyable 7. Costs associated with varying technologyable 7. Costs associated with varying technologyand management intensities.and management intensities.and management intensities.and management intensities.and management intensities.

TTTTTreatmentreatmentreatmentreatmentreatment Cost/wet ton ($) Cost/wet ton ($) Cost/wet ton ($) Cost/wet ton ($) Cost/wet ton ($)No turn 3.05Bucket loader-turned 6.74Turned 1x/2 weeks 14.34Turned 2x/week 41.23Source: Brinton, 1998

or compost use. For most feedstocks theywill either be “free” or you will receive a“tipping fee.” However, in some cases, youwill need to purchase bulking agents likewood chips or sawdust. Equipment costsinclude ownership, fuel and maintenance.Labor costs can divided into operations andmaintenance. It is wise to estimate these costsbefore starting a new composting operationto determine feasibility and pricing of saleablecompost products.

Composting regulations andComposting regulations andComposting regulations andComposting regulations andComposting regulations andpermitspermitspermitspermitspermitsIf you are composting on farm or compostsmall volumes of material (<20,000 cubicyards per year), you can compost without aspecial permit from the Wisconsin Department ofNatural Resources (DNR). However, most statesregulate large-scale composting. Many compostingfacilities must obtain composting permits to ensureminimal negative environmental impacts. For moreinformation, contact your state Department of NaturalResources. In Wisconsin, on-farm composting of cropresidues, manure and animal carcasses at the locationwhere they are produced are exempt from regulations,IF

• The facility is operated in a nuisance-free, environmentally sound manner.• The compost is land-spread in compliance with NR 518.04(1).• Composting of animal carcasses complies with s. 95-50(1).• Yard wastes and wood chips accepted from off-site are only used to increase C:N ratio of manure and the porosity of the pile, and meet minimum operation and design standards

Qualities of the Finished CompostQualities of the Finished CompostQualities of the Finished CompostQualities of the Finished CompostQualities of the Finished CompostNot all composts are created equal. What goes in asfeedstocks partly determines what comes out. Compostquality depends on the composting process used, thestate of biological activity, and, most importantly, theintended use of the compost. Just as beauty is in theeye of the beholder, the end use defines compostquality.

There are some specific chemical, physical andbiological parameters that can be used to evaluatecompost quality. For on-farm use as a soil amendment,a moisture content, organic matter content, C:N ratio

and pH should be determined before compostapplication (Table 8). High value markets likenurseries, landscaping, and turf require a high qualitycompost with specific qualities and characteristicssuitable for plant growth.

Compost Quality StandardsCompost Quality StandardsCompost Quality StandardsCompost Quality StandardsCompost Quality StandardsAside from temperature requirements to kill pathogens(55oC for at least 72 hrs.) and general acceptance ofUS EPA 503 Biosolids rules for trace metalconcentrations, there are no federal standards forfinished compost. Some states are in the process ofdeveloping standards to minimize negativeenvironment effects (pathogens, heavy metals andorganic pollutants). Other states require tests forbiological stability and compost-use related properties(salt content, pH, C:N ratio).

However, there are excellent programs dedicated toestablishing market-driven standards for the benefit ofcomposters and compost users: Two of theseprograms are the Seal of Testing Assurance (STA) by theUnited States Composting Council and the SolvitaQuality Seal of Approval by the Woods End ResearchGroup.

How the STA Program worksCompost producers regularly sample and test theirproduct, using STA Program approved labs, forchemical, physical and biological properties. All ofthese labs must use the same standardized testingmethodologies. Testing frequency is based on the eachproduction facility’s volume and can be as frequent asmonthly for the largest producers, to quarterly for the

TTTTTable 8. Qualities of compost for on-farm use and how to test.able 8. Qualities of compost for on-farm use and how to test.able 8. Qualities of compost for on-farm use and how to test.able 8. Qualities of compost for on-farm use and how to test.able 8. Qualities of compost for on-farm use and how to test.

QualityQualityQualityQualityQuality OptimumOptimumOptimumOptimumOptimum How to testHow to testHow to testHow to testHow to testSource of organic matter Should have a good Have organic matter tested

organic matter content by a soil lab

Source of nitrogen 10-15:1 C:N ratio Have C:N ratio checked bysoil lab

Neutral pH 6-8 Use soil pH kit at home orsoil lab

Low soluble salts If compost will be spread in the fall, no test necessary.If compost will be spread before planting, have soillab check that levels are below 10 dS

No phytotoxic compounds Good seed germination Plant 10 seeds in a small pot.

Weed-free No or few weed seeds Moisten compost and watchfor weed seedling growth.

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smaller composter. Compost use directions areprovided with the test results. The goal of the programis to provide a standard STA label to allow end users tocompare compost products and make an informedpurchasing decision. See their web site under Resourcesfor more detail.

The Solvita Quality Seal of ApprovalThe Woods End Solvita Quality Seal of Approvalprogram is based on specific, identified uses. Six end-use categories are presently recognized. The programprovides specific tests designed to assure users that aparticular compost or product meets basic qualityexpected for that particular use. Anyone who producesor distributes a compost or soil amendment product,may seek the Solvita Quality Seal of Approval. SeeResources for more information on their program.

SummarySummarySummarySummarySummaryComposting organic wastes is an environmentallysound means of recycling raw organic materials intovaluable soil amendments with many uses. As youbegin your composting operation, keep in mind thesefive points for a successful outcome:

• Be clear why you are making compost, and what you intend the final use of the compost to be.• Choose equipment and management methods based on your location and the intended use of the finished product.• Determine the right mix of ingredients to optimize C:N ratio, moisture content and porosity.• Monitor the composting process: temperature, oxygen, moisture and odors.• Test the finished compost to ensure it has the qualities you need for the intended use.

To your compost’s health!

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ResourcesResourcesResourcesResourcesResources

On-Farm Composting Handbook. Rynk R, 1992. NortheastRegional Agricultural Engineering Service Pub. No. 54.Cooperative Extension Service. Ithaca, N.Y. 1992;186pp. A classic in on-farm composting. $20 fromNRAES, Cooperative Extension, 607-255-7654 or 607-254-8770.email: nraes@cornell.edu. Website:www.nraes.org

The Field Guide to On-Farm Composting. 1999. 128 pages.A sturdy reference guide developed as a companion tothe NRAES publication. On-Farm CompostingHandbook (NRAES-54). $14.00 from NRAES - seephone numbers above.

Field Guide to Compost Use. The U.S. CompostingCouncil. 1996.

The Composters Answers Book. Volume 1. 1999.

Composting Manure for Value-Added Products. 2001.

Composting for Manure Management.Biocycle, Vol. 39, April 1998. http://www.jgpress.com/

WebsitesThe U.S. Composting Councilhttp://compostingcouncil.org/index.cfmpromotes research, public education, compoststandards and expansion of compost markets.

Woods End Research Laboratorypioneers in compost quality analysis and standards.http://www.woodsend.org/

Cornell Compostinghttp://www.cfe.cornell.edu/compost/Composting_homepage.html

US EPA's Composting Web Page http://www.epa.gov/compost/ includes Innovative Uses ofCompost and other EPA compost publications.

The California Quality Compost Council http://www.ccqc.org/

WasteNOT Organicswww.wastenot-organics.wisc.edu/wnoResearch-based information from the University ofWisconsin-Madison about organic by-products andtheir use as soil amendments.

BioCycle - Journal of Composting & Recycling on-linehttp://www.jgpress.com/

Recycler's World - equipment and serviceswww. Recycle.net/recycle/organic

Composting News on-line newletter for thecomposting industry http://www.recycle.cc/

Internet Recycling and Composting Resource Page -equipment and services http://www.recycle.cc/resource.htm

VermicompostingWorms for Composting from the ATTRA(Appropriate Technology Transfer for Rural Areas -pdf file 211K) www.attra.org/attra-pub/PDF/vermicomp.pdf

Worm Digest www.wormdigest.org/Email: mail@wormdigest.org

Compost RecipesThe Cornell Compost Recipe Maker. http://www.cfe.cornell.edu/compost/download.html.Downloadable Excel spreadsheets with compostmixture calculations for up to four ingredients (Mac orPC)

Compost Recipe Maker by Herb Brodie. An excellentDOS-based computer software program. $40 from PatLupo, University of Maryland. Tel: 301-405-1198.

Compost MaturitySolvita(r) Compost Maturity Test kits http://www.woodsend.org/solvita.htm

How Do I Know If My Compost Is Mature? TheCalifornia Compost Quality Council's maturity index(pdf file- 100 K) http://www.ccqc.org/downloads.htm

Compost Quality StandardsWoods End Compost Research Lab http://www.woodsend.orgSolvita Quality Seal of Approval program http://www.woodsend.org/sqa.htm

Seal of Testing Assurance Program (STA) http://tmecc.org/sta/index.html (from The U.S. CompostingCouncil at http://compostingcouncil.org/index.cfm)

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ReferencesReferencesReferencesReferencesReferences

Will Brinton, Jr. On farm composting evaluation of manureblends and handling methods for quality composts. (1998)Woods End Research Laboratory. Report to USDATech Center, Chester PA

Lopez Real, J. and M. Baptista. 1996. A preliminarycomparative study of three manure composting systems and theirinfluence on process parameters and methane emissions.Compost Science and Utilization Vol. 4, No. 3: 71-82.

Rynk, R. On-Farm Composting Handbook. NRAES Pub.54, 1992.

Cornell Waste Management Institute http://www.cfe.cornell.edu/compost/odors/inadeq.porosity.html#txt1

US Environmental Protection Agency, OrganicMaterials Management Strategy EPA530-R-97-003.Washington, DC. Government Printing Office, 1998.

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