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  1. 1. The Art andScience of CompostingA resource for farmers and compost producersLeslie Cooperband Wisconsin-MadisonUniversity of Wisconsin-MadisonCenter for Integrated Agricultural SystemsMarch 29, 2002
  2. 2. Table of ContentsThe Composting Process 1 Setting Up the Composting Environment 3 Determining Compost Mixes 5General Guidelines for Pile Management 5 Managing Foul Odors 6Siting Considerations, Technology Options and Management Intensity Levels 6 Siting Considerations 6 Composting Technologies 7Choosing a Composting Method 8Composting Regulations and Permits 11Qualities of the Finished Compost 11Compost Quality Standards 11Summary 12Resources 13
  3. 3. What is composting?Composting is controlled decomposition, the natural and horticultural applications and 0.6 million cubicbreakdown process of organic residues. Composting yards for land fill covers and surface mine remediationtransforms raw organic waste materials into biologically (U.S. EPA, 1998).stable, humic substances that make excellent soilamendments. Compost is easier to handle than manure Benefits of adding compost to soilsand other raw organic materials, stores well and is Compost is an organic matter source with a uniqueodor-free. ability to improve the chemical, physical, and biological characteristics of soils. It improves water retention inComposting is an ancient technology, practiced today sandy soils and promotes soil structure in clayey soilsat every scale from the backyard compost pile to large by increasing the stability of soil aggregates. Addingcommercial operations. There are Roman and biblical compost to soil increases soil fertility and cationreferences to composting. The nation’s first president, exchange capacity and can reduce fertilizerGeorge Washington, was also the nation’s first requirements up to 50%. Soil becomes microbiallyrecognized composter. Washington recognized the active and more suppressive to soil-borne and foliardegradative effects of farming on soil and he built a pathogens. Enhanced microbial activity also accelerates“dung repository” to make compost from the animal the breakdown of pesticides and other syntheticmanures so he could replenish the soil’s organic matter. organic compounds. Compost amendments reduce the bioavailability of heavy metals—an important quality inUses and markets for compost the remediation of contaminated soils.As landfills reach their capacity and ban acceptance oforganic wastes, composting is an increasingly viable The Composting Processmeans of organic waste management. Composting Composting occurs through the activity ofanimal manures can also be a solution to manure microorganisms naturally found in soils. Under naturalmanagement on the farm. Most importantly, the final conditions, earthworms, nematodes and soil insectsproduct is a valuable soil resource. Compost can such as mites, sowbugs, springtails, ants, and beetles doreplace materials like peat and topsoil as seed starters, most of the initial mechanical breakdown of organiccontainer mixes, soil amendments, mulches and natural materials into smaller particles. Under controlledfertilizers in commercial greenhouse production, farms,landscaping, turf and land remediation (Table 1). The Composting ProcessThere is a big potential demand for compost in plant Heat Waterproduction-related industries—close to 900 million CO2cubic yards of compost could be used in agricultural Organic Matter Minerals OrganicTable 1. Compost Markets and Use Compost matter, minerals, Water Pile water, Micro- microbesMarket Compost Use organismsAgronomic Soil amendment Raw Materials Finished compostHorticultural Seed starter, soil amendment, O2 mulch, container mix, natural fertilizerUrban/suburban Soil amendment, mulch Figure 1. The Composting Process. Adapted from Rynk,landscaping 1992.Turf Seed starter, soil amendment, topsoil, natural fertilizer, mulch conditions, composters break down large particlesForestry Seed starter, soil amendment, through grinding or chopping. Once optimal physical topsoil, mulch conditions are established, soil bacteria, fungi, actinomycetes and protozoa colonize the organicLand reclamation Soil amendment, mulchBioremediation material and initiate the composting process (FigureLand fill cover1
  4. 4. 1.) These mesophilic organisms function best at warm amended to container mixes or the soil.temperatures (50-113oF). There is no clearly defined time for curing. CommonThe active phase of composting practices in commercial composting operations rangeAs temperatures in the compost pile increase, from one to four months. Homeowner compost pilesthermophiles (microorganisms that function at can cure for as long as six to twelve months.temperatures above 113oF) take over. The temperaturein the compost pile typically increases rapidly to 130- When is the compost finished?150 oF within 24-72 hours of pile formation, which is There is no fixed time to produce finished compost.maintained for several weeks. This is called the active Duration depends on feedstocks, composting methodphase of composting (Figure 2, 3). used and management. It can take as little as three months and as long as two years. Compost isIn the active “thermophilic” phase, temperatures are considered finished when the raw feedstocks are nohigh enough to kill pathogens and weed seeds and to longer actively decomposing and are biologically andbreak down phytotoxic compounds (organic chemically stable. Some practitioners refer to finishedcompounds toxic to plants). Common pathogens killed compost as stable; refering to the state of biologicalin this phase are Escherichia coli, Staphylococcus aureus, activity. Maturity is usually defined as the degree ofBacillus subtillus, and Clostridium botulinum. During this humification (conversion of organic compounds tophase, oxygen must be replenished through passive or humic substances, which are most resistant toforced aeration, or turning the compost pile. microbial breakdown). It is easier to measure compost stability than maturity, so most composters measureThe curing phase temperature or compost respiration (oxygenAs the active composting phase subsides, temperatures consumption). When the temperature at the center ofgradually decline to around 100oF. The mesophilic the pile returns to near-ambient levels and oxygenmicroorganisms recolonize the pile, and the compost concentrations in the middle of the pile remain greater than 10-15% for several days, compost is considered stable or finished. These measurements should be taken when the compost pile has at least 50% moisture A=mesophilic content by weight. 160 B=thermophilicTemperature 140 C=mesophilic 120 It is important to learn how to assess the maturity or D-maturation stability of the compost because stability will affect oF 100 90 Active Phase Curing Phase many of the chemical and biological properties of the 70 compost, and ultimately how the compost can be used. 50 “Stability indices” and maturity/stability testing are A B C D available from compost research and education Time organizations (see Resources). Immature or biologically unstable composts can be used on farms asFigure 2. Temperature changes in an average compost Temperaturepile.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:N Figure 3. Steaming compost pile during active,ratios, extreme pH values or high salt contents, all of thermophilic phase of composting, when compost temperatures can reach as high as 150o Fwhich can damage or kill plants if the compost is 2
  5. 5. a soil amendment ONLY IF applied several months composting are listed in Table 2.prior to planting. Immature composts can also be usedin site remediation, and as land fill covers. Feedstocks: the quality of the microbial “food” Composts can be made from most organic by-Setting Up the Composting Environment products. Common feedstocks are poultry, hog andSince composting is a microbial process, providing the cattle manures, food processing wastes, sewage sludge,right environment for microbes is crucial for successful municipal leaves, brush and grass clippings, sawdust,composting. In other words, feed the microbes and let and other by-products of wood processing.them do the work for you! Three factors interact in the Ideally, several raw materials should be mixed together to create the “ideal” range of conditions listed in TableTable 2. Optimal conditions for rapid, aerobiccomposting (Adapted from Rynk, 1992) 2. However, in the real world this can’t always happen. Fortunately composting is a forgiving process that canCondition Acceptable Ideal occur over a wide range of conditions, and if you mix materials with an eye to an acceptable moisture contentC:N ratios of combined 20:1 to 40:1 25-35:1feedstocks and carbon-to-nitrogen ratio (Table 3), you can produce acceptable compost with good management practices.Moisture content 40-65% 45-60% by weight In general, the combination of feedstock quality andAvailable oxygen >5% >10% or more compost management will determine the quality ofconcentration the finished product.Feedstock particle size < 1 inch Variable The supply of carbon (C) relative to nitrogen (N) is anBulk density 1000 lbs./cu yd 1000 lbs./cu yd important quality of compost feedstocks. It ispH 5.5-9.0 6.5-8.0 designated as the C:N ratio. The ideal starting range is C:N 25:1 to 35:1. As a general rule, if the C:N ratio isTemperature 110-150o F 130-140o F greater than 20:1, microbes will use all the N for their (43-66o C.) (54-60o C) own metabolic needs. If the C:N ratio is lower than 20:1, they have surplus N and it can be lost to the atmosphere as ammonia gas and cause odor problems.making of good compost: • the chemical makeup of the raw organic ingredients, called feedstocks Table 3. Common feedstocks and their characteristics • the physical size and shape of the feedstocks (Adapted from Rynk, 1992, and other sources to illustrate (porosity of the pile) representative values) • the population of organisms involved in the Feedstock Moisture content C:N Bulk Density composting process. High in CarbonAerobic vs. anaerobic composting Hay 8-10 15-30 -Compost “happens” either aerobically (with oxygen) or Corn stalks 12 60-70 32anaerobically (without oxygen) when organic materials Straw 5-20 40-150 50-400 Corn silage 65-68 40 -are mixed and piled together. Aerobic composting is Fall leaves - 30-80 100-300the most efficient form of decomposition, and Sawdust 20-60 200-700 350-450produces finished compost in the shortest time. If the Brush, wood chips - 100-500 - Bark (paper mill waste)- 100-130 -proper amounts of food (carbon), nutrients, water and Newspaper 3-8 400-800 200-250air are provided, aerobic organisms will dominate the Cardboard 8 500 250compost pile and decompose the raw organic materials Mixed paper - 150-200 - High in Nitrogenmost efficiently. Pile “heat” is a by-product of Dairy manure 80 5-25 1400biological “burning”—the aerobic oxidation of organic Poultry manure 20-40 5-15 1500matter to carbon dioxide so that microbes can generate Hog manure 65-80 10-20 - Cull potatoes 70-80 18 1500energy. Optimal conditions for rapid, aerobic Vegetable wastes - 10-20 - Coffee grounds - 20 - Grass clippings - 15-25 - Sewage sludge - 9-25 -3
  6. 6. Green materials usually have lower C:N ratios than moisture content by drying and weighing.woody materials or dead leaves. Animal wastes are moreN rich than plant wastes (Table 3). A common and effective feedstock combination on farms is manure (high in N, high in moisture),The complexity of the carbon compounds also affects combined with straw bedding (high in C, low inthe rate at which organic wastes are broken down. The moisture). Be sure there is enough straw or other dry material in the mixture. Estimating the carbon content of feedstocks pH and temperature The acidity or alkalinity of the organic materials, % carbon = %volatile solids measured by the pH value, affects the growth of 1.8 where %volatile solids = 100 - %ash (material microorganisms. Bacterial decomposers prefer a pH incinerated at 500o C.) range 6.0-7.5 while fungal decomposers prefer pH range 5.5-8.0. If the compost pH exceeds 7.5, gaseous losses of ammonia are more likely to occur. Certainease with which compounds degrade generally follows materials such as dairy manure, paper processingthe order: carbohydrates > hemicellulose > cellulose =chitin > lignin. Fruit and vegetable wastes are easilydegraded because they contain mostly simple How to calculate the moisture content ofcarbohydrates (sugars and starches). In contrast, leaves, compost or feedstockstems, nutshells, bark and trees decompose moreslowly because they contain cellulose, hemicellulose Materials needed: small container, scale, samples of compost or feedstocksand lignin. 1. Weigh the empty container. 2. Add 10 g of the material into theWater Requirements container (this is the wet weight).The ideal moisture content of the compost pile is 3. Dry the sample for 24 hours in a 110oC oven.between 45-60% by weight. This should feel moist to 4. Reweigh the sample and subtract the weight of the container. This is the dry weight.the touch when you squeeze a handful of blended Determine the moisture content usingfeedstocks. The material should hold together but not the following equation:exude excess water. Moisture content = 100 X (wet weight ñ dry weight)Low moisture content will slow the composting wet weightprocess. Moisture also regulates temperature. Drierpiles tend to heat up and cool down more rapidly thanwetter piles, and excessive dryness makes piles wastes and cement kiln dust can raise pH, while foodsusceptible to spontaneous combustion. Moisture processing wastes or pine needles can lower pH.content in excess of 60% means pore spaces in thecompost pile will be filled with water rather than air, Measure pH at the beginning and end of composting.leading to anaerobic conditions. Send samples to a soil lab for saturated paste pH and EC measurements (electrical conductivity or solubleFeedstocks with different moisture contents can be salts). You can also monitor pH using the soil pH kitsblended to achieve ideal moisture content. from farm and garden catalogs.Carbonaceous materials like newspaper, and wood by- Ambient air temperatures affect microbial growth andproducts like sawdust can be used as bulking (drying) activity in the compost pile, and hence the rate atagents. Chipped brush, wood chips, and bark can be which the raw materials decompose. In temperateadded to fine particle feedstocks to create large pore climates, composting is fastest in spring, summer andspaces. If you cant achieve the ideal moisture content fall months and is likely to come to a complete standby blending feedstocks alone, you can add water to still in winter months. However, if pile size is increasedmaterials as you blend them. Take samples and measure in winter to 8-12 feet tall and 10-12 feet wide, piles can 4
  7. 7. retain heat and remain active. much nitrogen is present, which can be corrected by mixing in carbon-rich materials. A putrid odor canDetermining compost mixes mean too much water—correct by mixing in bulkingMany composters determine their feedstock mix by materials (see Table 3).the look and feel of the mix. With an eye tooptimizing C:N ratio and moisture content, and some Good aeration can also be achieved by managing pileexperience with the raw materials, this trial and error porosity. Porosity is defined as the volume of poresapproach can often work. For composters trying out divided by the total volume of compost. Some ofnew materials, for larger operations, or when those pores will be filled with water and the rest withcomposting needs to be efficient, more precise air. The initial pile mix should have between 45-60%compost recipes can be calculated using formulas and air-filled porosity and during the active phase ofcomputer spreadsheet programs that are based on the composting, it shouldnt drop below 35% (see sidebar:characteristics of the raw materials (see Resources). How to measure bulk density and porosity).General Guidelines for Pile Managing Pile MoistureManagement Water will be given off as vapor during the active phase of composting, when temperatures are high. IfManaging compost piles for goodaerationA well-aerated compost pile has at least5% oxygen content during the active phase How to measure pile bulk density and air-filled porosityof composting (ideally closer to 10%).Composts must be aerated either passively First determine bulk density (the weight per unit volume of your combined feedstocks). Weigh the container (5 gallon bucket) empty. Add material 1/3 full, tapor actively as aeration is key to successful the bucket five times on a flat hard surface, add another 1/3 of material, tap fivecomposting. As microbial activity increases times again, then fill to top without tapping. Weigh filled bucket and the compost pile, more oxygen will be Determine bulk density using the calculations below.consumed. If the oxygen supply is not Material measured Examplereplenished, composting can shift to 1. Weight of bucket with material (lb) 20.5 2. Weight of empty bucket 2.0anaerobic decomposition, slowing of the 3. Weight of material (line 1- line 2) 18.5composting process and foul odors. 4. Bulk density (lbs/cubic yards) yards)= 740 (line 3 X 40). Note: this conversion factor only works for a 5-gallon bucket.Oxygen monitoring equipment is available,but is expensive. Temperature, odors and Take the full bucket with material and fill with water. Use the spreadsheetmoisture are easy to measure and provide a (%). below to calculate air-filled porosity (%)good indication of active decomposition Material measured Exampleand adequate aeration. Monitor 1. Weight of bucket withtemperature at least weekly, using a material + water (lb) 46.5 2. Weight of bucket withthermometer with a three-foot stem and a material (from line 1 in bulk density table) 20.5range from 0 to 200 degrees F. Check the 3. Weight of water (line 1- line 2) 26moisture content and odor. A compost 4. % air-filled porosity = 62% (line 3 X 2.4)pile is not odor-free, but a distinct foulodor usually means anaerobic conditionshave developed. An ammonia smell can mean too you are turning piles, you can add water as you turn. If you are using static aeration, it is much more Taking the temperature of your compost pile ∑ Use a probe with a 3 foot stem. difficult to add water to the compost pile. It is best to ∑ Leave in place long enough for the reading to make initial feedstock blends on the wet side (65-70%) stabilize. by weight, so that when they lose moisture vapor, they ∑ Take readings in several locations ñ at different will still be wet enough to keep microbes active. Some depths from the top and sides. ∑ Find the hottest pockets. commercial composters using forced aeration systems ∑ Graph your findings as in Figure 2. add moisture by introducing humidified air into pipes5
  8. 8. that blow air into the piles. To get aerobic bacteria breathing again Pile size The ideal height and width of the piles will depend on ∑ Mix wet feedstocks with coarse, dry bulking the porosity and moisture content of the raw materials, agents as soon as they come on site. ∑ Create adequate porosity in compost piles by composting method and your specific equipment increasing the number and sizes of pores, such (Table 4). For example, a light, dry pile can be stacked as adding wood chips. higher than a wet, dense pile, without the risk of ∑ Build piles to maximize temperature-driven convective air flowTable 4. Pile size guidelines decrease and airflow within the compost pile will be Composting method Height (feet) Width (feet) restricted. A mix of particle sizes creates the most Static Piles 3-6 12 porous pile (Figure 4). PAWS 3-6 10 Windrow Composting - Tractor pulled 6-8 10 Managing Foul Odors Self-propelled turner 3-9 9-20 Good aeration promotes active aerobic Bucket loader 6-12 10-20 decomposition. When piles are too wet, too large, not Aerated Static Piles 6-12 10-20 porous enough, or are degrading too quickly, aerobic In-vessel NA NA bacteria can’t get enough oxygen and anaerobic bacteria take over. Sulfur compounds and other by- products of anaerobic respiration form and odors build. Odors can originate from specific incoming or developing anaerobic conditions within the pile. Small stockpiled feedstocks (such as sewage sludge, liquid piles will be able to maintain higher internal oxygen manure or fish by-products) or poorly aerated concentrations than large piles, but large piles will compost piles. Anaerobic respiration, and resulting retain the higher temperatures better than small piles. odors, can also occur in standing pools of water For a pile to heat and stay hot, the minimum size around compost windrows and in water retention should be one cubic yard. ponds. You can minimize odors by proper pile management. Once aerobic conditions are The particle size of the feedstock will affect porosity, reestablished, the bacteria will “eat” the odorous airflow, and the amount of microbial activity. Smaller compounds. particles have more surface area per unit volume and, therefore, microbes have more surface to colonize. Ammonia However, if particles are too small, porosity will Ammonia odors can form independent of the aeration of the feedstocks or piles. Nitrogen-rich feedstocks usually have low C:N ratios. If N is in excess, nitrogen is metabolized in a way that gaseous N compounds (ammonia and nitrous oxide) are released. To minimize this, set pile C:N well above 10:1 (25-35:1 ideal) and try to blend feedstocks to Loosely packed, Loosely packed, keep the pile pH below 7.5. well structured uniform particle size Siting Considerations, Technology Options and Management Intensity Levels Tightly packed, Tightly packed, mixed uniform particle size Siting Considerations particle sizes In choosing a site, consider • Management operations: access to roads and ease of handling materials T.Figure 4. How porosity affects aeration. From T. Richard, WasteCornell Waste Management Institute. • Water quality protection: siting is the first step in preventing leaching and run-off into 6
  9. 9. surface or groundwater • Neighborhood relations: odor, noise, dust, debris and appearance of your operationLeaching of nitrates and other soluble nutrients ismost likely to occur during curing phase and compost Figure 5. Although windrow composting uses morestorage. Highly permeable soils are most at risk. Try to land than other methods, it can be put in the fieldfind a soil of intermediate permeability. Ideally, the site where the compost is to be appliedshould be several feet above the seasonally high watertable, and several hundred feet away from wells or quite heterogeneous.surface water. Consider the slope of the site, especiallythe potential for water to run into the compost piles Windrow Compostingduring storms or snowmelt. Plant grass buffer strips to Windrow is the general term for an elongated pile ofslow run-off. Consider providing roofs over some of stacked raw materials. (Figure 5). Piles need to bethe composting area to divert precipitation and keep small (3-6’) and porous enough for air to pass throughstored compost dry. them over a long period of time.Site visibility and appearance can go a long way in A turned windrow is one that is mechanically turnedmaintaining a good perception of your operation. Use using a bucket loader, manure spreader or a windrowsome of your compost to landscape the site, plant and turner (Figure 6A,B). Turning the windrow remixesmaintain trees and grassy areas—these will also help the materials, allowing all the raw materials to becontrol and filter run-off from the composting site. colonized by microorganisms in the warmer, moreChoose a site with some consideration of the homes active internal part of the compost pile. Oxygen isof neighbors and the direction of prevailing winds reintroduced, heat, water vapor and gases escape. Theduring warm weather. Plan grinding and turning for most important part of turning the pile is thehours during the day in which neighbors are less likely reestablishment of porosity and the ability of air to getto be affected by the odors and noise. into the pile. TechnologiesComposting Technologies Passively aerated windrow system (PAWS)The most common composting technologies or PAWS includes perforated pipes placed at the base ofmethods are each windrow to promote convective airflow • Static piles throughout the pile. The key to this system is thorough • windrow composting premixing of feedstocks before placing on the • passively aerated windrows perforated pipes. Also, windrows need to be insulated • forced aeration, static piles with finished compost to ensure thermophilic • enclosed, or in-vessel, composting temperatures reach the outer edges of the windrow • vermicomposting. (Figure 6C).Within these methods are ranges of technologyoptions. Forced Aerated Static Piles Forced aerated static piles are similar to PAWS piles,Static Piles but blowers are installed at the ends of perforatedStatic piles are the simplest form of composting and pipes or air ducts as shown in Figure 7. Air flow canrequire little management and equipment. Once be adjusted by changing the frequency and duration ofestablished, it is very difficult to adjust moisture, and the blower. Usually, blowers are set to turn on whenstatic piles tend to go anaerobic in the center. Aerobic the compost reaches a maximum temperature (e.g.,conditions can be achieved if the initial pile porosity is 150oF).high (>60%) and there is a high proportion of bulkingmaterials to keep pores open for air exchange. While Enclosed Compostingsimple, this method takes the longest to produce Enclosed, or in-vessel, composting is mainly for thefinished compost, and the composted material can be commercial compost producer who needs more7
  10. 10. environmental control during the composting process. Some large scale composting operations use completely enclosed in-vessel equipment to achieve maximum control of temperature, oxygen and moisture. Some farms have also successfully used the smaller, less expensive bin equipment. Equipment ranges from a simple enclosed bin, an agitated bin or reactor, to an entire building devoted to composting. Vermicomposting Vermicomposting is worm composting; in which red worms transform decaying organic matter into wormFigure 6a. Mixing poultry litter and agriculturalbyproducts in a feed mixer for passive aerationcomposting Figure 7. Pipes are inserted into static aerated compost piles. castings. The castings contain high concentrations of readily available nutrients for plants. Vermicomposting does not achieve the high (thermophilic) temperatures in windrow and aerated static pile composting because the worms cant survive the high temperatures. However, research has shown that both pathogens and weed seeds can be destroyed in vermicomposting.Figure 6b. Using a tractor-pulled windrow turner to mix Vermicomposting is usually done in containers and cancannery wastes with sawdust and municipal leaves be done indoors and outdoors, allowing year round composting. The two types of worms best suited to worm composting are the red worms: Eisenia foetida (commonly known as red wiggler, brandling, or manure worm) and Lumbricus rubellus. They are often found in the litter layers of forests, manure piles and backyard compost heaps. For more information see Resources. Choosing a composting method Choose an approach that best suits your reasons for making compost, the location of the compost site and the amount of specialized equipment you have available to produce compost (Figure 8). Where you are located is important from environmental impact and potential nuisance perspectives. For example, composters located in rural areas need to be TurningFigure 6c. Turning poultry litter using a self-propelled concerned that composting activities dont adverselywindrow turner affect surface and ground waters, but they usually are 8
  11. 11. Decision tree for identifying composting options Who are you? Farm Municipality Commercial composter Why do you want On-farm Saleable Free, give Saleable Saleable to make compost? use product away product product Rural- Rural- Rural- Rural- Urban Rural- Where are you Rural Rural Urban Rural Urban urban urban urban urban urban located? Low Low- Intermediate Intermediate- Low- Intermediate High Management Static, intermediate Manure high intermediate Tractor pulled Windrow intensity/ passively Have access spreader, Tractor pullled Bucket loader, turner, forced turning equip- appropriate aerated piles to equipment: PAWS turners, forced manure aeration (low- ment, enclosed technology manure aeration spreader tech) facilities, spreader forced aeration Figure 8. Choose an approach that best suits your reasons for making compost, the location of the compost site and the amount of specialized equipment you have available to produce compost.less concerned about neighbor complaints related to non-specialized equipment. The most commonodors, noise and dust. Composting sites located in example is building and turning piles using a manurerural-urban and urban areas often are forced to use spreader. These windrows would likely be turnedhigh technology options to minimize nuisance once per week during the active phase of compostingcomplaints. and then monthly during the curing phase. The passively aerated windrow system (PAWS) would alsoThe decisions about technology options and be considered an intermediate technology optionmanagement intensity can be viewed as a continuum because the composter will need some kind of(Figure 8). If you are new to composting and want to equipment to premix feedstocks and will need tomake compost exclusively for your own use, you might purchase perforated pipe for placement underneathstart out at the low to intermediate scale. Later if you the compost pile. Management of the PAWS system isdecide to make a saleable product or expand your site, intensive in the pile establishment phase, but minimalyou might decide that you can justify the costs of thereafter. Both of these intermediate technologyhigher technologies and more intensive management. options are suited to rural or rural-urban fringe locations. Composts produced using these methods“Low technology” composting would be best suited to internal use, unless theLow technology options usually go hand-in-hand with composter can demonstrate product consistency overminimal management. Examples include static, time.passively aerated piles where you would use dry andlarge-particle size feedstocks to give the compost pile “High technology” compostingsufficient porosity. Use of a bucket loader to turn piles High technology options usually include specializedinfrequently (every two weeks) would also be composting equipment: tractor-pulled or self-considered a low-technology option for on-farm propelled windrow turners, forced aeration systemscomposting. These options make the most sense for with perforated pipes and blowers and enclosed (or in-individuals in rural areas making compost largely for vessel) systems. These require serious financial andtheir own use. labor commitments. Use of these technologies are justified when the composter intends to make a“Intermediate” technology options saleable product and when the compost site is locatedIntermediate technology - moderate management either on the rural-urban boundary or within an urbanintensity includes turned windrow composting using setting. Management intensity of these systems is9
  12. 12. Table 6. Technology and management effects on total losses Technology usually high. For turned windrow systems, of organic matter and nitrogen during composting. windrows are usually turned 2-3x/week Treatment Organic Matter loss (%) Total Nitrogen loss (%) during the active phase of composting (minimum of 1x/week) and then 1-2x/ Cow manure compost at 120 days month during curing. For the forced-aerated No turn 70 51 Bucket loader-turned 78 60 and enclosed technologies, you will need to Turned 1x/2 weeks 73 53 monitor the equipment to make sure that air Turned 2x/week 80 64 flow and moisture are optimized to produce Poultry manure compost at 150 days the desired temperature range. No turn 75 72 Bucket loader-turned 79 76 Studies comparing technology- Turned 1x/2 weeks 79 78 Turned 2x/week 88 86 management effects on compost Source: Brinton, 1998 quality. quality. There are several studies evaluating the range of composting technologies from no turning to effects of different composting technologies and highly specialized self-propelled windrow turners management intensities on compost “process (Brinton, 1998). The evaluated compost pile variables” (measurements used to assess how the temperature and oxygen, organic matter and nitrogen process is progressing) and finished compost. Lopez loss and operations & maintenance costs. Results Real and Baptista (1996) evaluated three composting showed that use of a turning machine reduced the time methods to determine their effects on composting to finished compost by a few weeks compared to no process variables and methane emissions. The methods turning or use of a manure spreader. When temperature profiles were compared,Table 5. Percent change in compost total volume and volatile solids intensification of the composting processfor three manure composting methods over a 36 day period. either through turning or adding bulkingAverage methane emissions over the same period. material to increase porosity decreased the time to “stable” compost by approximately 20 days.Process variable Minimal intervention Windrow Forced Aeration % change over time As management intensification increased, soVolume reduction 55 73 55 did loss of organic matter and nitrogen (TableVolatile solids 12 22 15 6). However, the costs associated withAverage methaneemission (ppmv) 28,744 223 3 technology and management also increased ppmv = parts per million per volume with intensification (Table 7). They concluded that if the goal for composting is nutrient management and on-farm use of compost, intensive technologies and management are not included 1) minimal intervention or passively aerated necessary. stacked manure; 2) windrowing or turned mechanically with a manure spreader and 3) forced aeration using perforated pipes and a blower. They evaluated changes Cost Considerations in the first 36 days of composting and found that These can be grouped into six general windrowing produced the greatest change in total categories: 1) business and site development (most volume and volatile solids compared to minimal applicable to larger scale operations or permitted intervention and forced aeration (Table 5). Methane facilities), 2) feedstock costs, 3) equipment, 4) labor; 5) emissions from the passively aerated piles were over management (for large facilities) and 6) marketing and/ 100 times greater than the windrow turned piles and 1000 times greater than the forced aeration piles. Table 7. Costs associated with varying technology and management intensities. Results showed that introducing air mechanically speeds up the composting process and greatly reduces Treatment Cost/wet ton ($) emissions of a greenhouse gas (methane). No turn 3.05 Bucket loader-turned 6.74 Turned 1x/2 weeks 14.34 Woods End Research Labs in Maine presented Turned 2x/week 41.23 findings from two manure compost studies using a Source: Brinton, 1998 10
  13. 13. Table 8. Qualities of compost for on-farm use and how to test.or compost use. For most feedstocks theywill either be “free” or you will receive a Quality Optimum How to test“tipping fee.” However, in some cases, you Source of organic matter Should have a good Have organic matter testedwill need to purchase bulking agents like organic matter content by a soil labwood chips or sawdust. Equipment costs Source of nitrogen 10-15:1 C:N ratio Have C:N ratio checked byinclude ownership, fuel and maintenance. soil labLabor costs can divided into operations and Neutral pH 6-8 Use soil pH kit at home ormaintenance. It is wise to estimate these costs soil labbefore starting a new composting operationto determine feasibility and pricing of saleable Low soluble salts If compost will be spread in the fall, no test necessary. If compost will be spread before planting, have soilcompost products. lab check that levels are below 10 dSComposting regulations and No phytotoxic compounds Good seed germination Plant 10 seeds in a small pot.permits Weed-free No or few weed seeds Moisten compost and watchIf you are composting on farm or compost for weed seedling growth.small volumes of material (<20,000 cubicyards per year), you can compost without aspecial permit from the Wisconsin Department of and pH should be determined before compostNatural Resources (DNR). However, most states application (Table 8). High value markets likeregulate large-scale composting. Many composting nurseries, landscaping, and turf require a high qualityfacilities must obtain composting permits to ensure compost with specific qualities and characteristicsminimal negative environmental impacts. For more suitable for plant growth.information, contact your state Department of NaturalResources. In Wisconsin, on-farm composting of crop Compost Quality Standardsresidues, manure and animal carcasses at the location Aside from temperature requirements to kill pathogenswhere they are produced are exempt from regulations, (55oC for at least 72 hrs.) and general acceptance ofIF US EPA 503 Biosolids rules for trace metal • The facility is operated in a nuisance-free, concentrations, there are no federal standards for environmentally sound manner. finished compost. Some states are in the process of • The compost is land-spread in compliance developing standards to minimize negative with NR 518.04(1). environment effects (pathogens, heavy metals and • Composting of animal carcasses complies organic pollutants). Other states require tests for with s. 95-50(1). biological stability and compost-use related properties • Yard wastes and wood chips accepted from (salt content, pH, C:N ratio). off-site are only used to increase C:N ratio of manure and the porosity of the pile, and meet However, there are excellent programs dedicated to minimum operation and design standards establishing market-driven standards for the benefit of composters and compost users: Two of theseQualities of the Finished Compost programs are the Seal of Testing Assurance (STA) by theNot all composts are created equal. What goes in as United States Composting Council and the Solvitafeedstocks partly determines what comes out. Compost Quality Seal of Approval by the Woods End Researchquality depends on the composting process used, the Group.state of biological activity, and, most importantly, theintended use of the compost. Just as beauty is in the How the STA Program workseye of the beholder, the end use defines compost Compost producers regularly sample and test theirquality. product, using STA Program approved labs, for chemical, physical and biological properties. All ofThere are some specific chemical, physical and these labs must use the same standardized testingbiological parameters that can be used to evaluate methodologies. Testing frequency is based on the eachcompost quality. For on-farm use as a soil amendment, production facility’s volume and can be as frequent asa moisture content, organic matter content, C:N ratio monthly for the largest producers, to quarterly for the11
  14. 14. 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.SummaryComposting 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! 12
  15. 15. Resources BioCycle - Journal of Composting & Recycling on-line Composting Handbook. Rynk R, 1992. NortheastRegional Agricultural Engineering Service Pub. No. 54. Recyclers World - equipment and servicesCooperative Extension Service. Ithaca, N.Y. 1992; www. A classic in on-farm composting. $20 fromNRAES, Cooperative Extension, 607-255-7654 or 607- Composting News on-line newletter for Website: composting industry Internet Recycling and Composting Resource Page -The Field Guide to On-Farm Composting. 1999. 128 pages. equipment and services sturdy reference guide developed as a companion to resource.htmthe NRAES publication. On-Farm CompostingHandbook (NRAES-54). $14.00 from NRAES - see Vermicompostingphone numbers above. Worms for Composting from the ATTRA (Appropriate Technology Transfer for Rural Areas -Field Guide to Compost Use. The U.S. Composting pdf file 211K) 1996. vermicomp.pdfThe Composters Answers Book. Volume 1. 1999. Worm Digest Email: mail@wormdigest.orgComposting Manure for Value-Added Products. 2001. Compost RecipesComposting for Manure Management. The Cornell Compost Recipe Maker. http://Biocycle, Vol. 39, April 1998. http:// Downloadable Excel spreadsheets with compost mixture calculations for up to four ingredients (Mac orWebsites PC)The U.S. Composting Council Compost Recipe Maker by Herb Brodie. An excellentpromotes research, public education, compost DOS-based computer software program. $40 from Patstandards and expansion of compost markets. Lupo, University of Maryland. Tel: 301-405-1198.Woods End Research Laboratory Compost Maturitypioneers in compost quality analysis and standards. Solvita(r) Compost Maturity Test kits http:// Composting How Do I Know If My Compost Is Mature? The California Compost Quality Councils maturity indexComposting_homepage.html (pdf file- 100 K) EPAs Composting Web Page http:// Compost Quality includes Innovative Uses of Woods End Compost Research Lab http://Compost and other EPA compost publications. Solvita Quality Seal of Approval program http://The California Quality Compost Council http:// Seal of Testing Assurance Program (STA) http://WasteNOT Organics (from The U.S. Council at information from the University ofWisconsin-Madison about organic by-products andtheir use as soil amendments.13
  16. 16. ReferencesWill Brinton, Jr. On farm composting evaluation of manureblends and handling methods for quality composts. (1998)Woods End Research Laboratory. Report to USDATech Center, Chester PALopez 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 Environmental Protection Agency, OrganicMaterials Management Strategy EPA530-R-97-003.Washington, DC. Government Printing Office, 1998. 14