Compost is made by recycling organic materials such as yard trimmings, wood chips, food scraps, and animal manures in a controlled process. The process employs microorganisms to transform the raw materials so that they are no longer recognizable. Quality compost is thoroughly decomposed and pathogen-free. The possible presence of pathogenic microorganisms in compost is a major challenge for compost producers. Composted animal manures can be used in many beneficial products, but they must be properly processed. The most important conditions with respect to sanitization are: the composting process must be thorough; the composting process must be complete; and, the finished compost must not be reinoculated with pathogens

Hollyer, James R.

LeaMaster, Brad

Sullivan, Jennifer L.

ScholarSpace at University of Hawai'i at Manoa

Cooperative Extension Service Animal Waste ManagementJuly 1998AWM-1Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June30, 1914, in cooperation with the U.S. Department of Agriculture. Charles W. Laughlin, Director and Dean, Cooperative Extension Service, CTAHR, Universityof Hawaii at Manoa, Honolulu, Hawaii 96822. An equal opportunity / affirmative action institution providing programs and services to the people of Hawaii withoutregard to race, sex, age, religion, color, national origin, ancestry, disability, marital status, arrest and court record, sexual orientation, or veteran status.Composted Animal Manures:Precautions and ProcessingCompost is made by recycling organic materials suchas yard trimmings, wood chips, food scraps, andanimal manures in a controlled process. The processemploys microorganisms to transform the raw materi-als so that they are no longer recognizable. Finishedcompost is a crumbly, earthy-smelling, dark materialthat looks like a commercial potting-soil mixture. Usedas a soil amendment, compost can• improve soil structure, making the soil easier to cul-tivate and encouraging root development• provide plant nutrients and enable their increaseduptake by plants• aid water absorption and retention by the soil, reduc-ing erosion and run-off and thereby protecting sur-face waters from sedimentation• help bind agricultural chemicals, keeping them outof waterways and protecting groundwater from con-tamination• increase levels of beneficial soil organismsQuality compost is thoroughly decomposed andpathogen-free. Pathogens hazardous to human health canbe introduced to compost when animal manures (urineand feces) are used as raw materials. Various kinds ofanimal manures are available in Hawaii, and this publi-cation is written to inform those who might be consid-ering the use of animal manures in composting.Indiscriminate use of compost products that containpathogens can create health risks for humans and ani-mals by dispersing pathogens into the environment.Therefore, it is important that when animal manures areused, the resulting compost products have been suffi-ciently sanitized to reduce pathogen contents to levelslower than those normally considered “risk levels.”Composting and sanitizationIn composting, many types of nonpathogenic microor-ganisms transform complex organic materials into sim-pler compounds through the decomposition processesof mineralization and humification. When a compost pileis correctly constructed and managed, the activity of thesedecomposer microorganisms generates heat sufficient tokill pathogenic microorganisms. If the right conditionsare not present for the decomposition activity to gener-ate heat, the process may not result in sanitization.For sanitization to take place during the compostingprocess, the entire mass of organic material must beexposed to lethal temperatures for a suitable length oftime. Because these temperatures develop in the inte-rior of the pile, turning the pile is an important part ofcompost management. Undecomposed material from thetop and sides of the pile are rotated toward its center byturning the pile. After several turnings, usually at inter-vals ranging from one to three weeks, all of the materi-als in the pile should have been exposed to the condi-tions that result in sanitization.Composting is completed when the pile no longergenerates heat and the original organic materials are nolonger recognizable. The composting process has thenreached an endpoint and is more or less biologicallystable. Finished compost is not a good substrate forgrowth of pathogens, but if it has been recontaminatedwith fresh manure, it may act as a carrier for pathogens.Prepared by Brad LeaMaster1, James R. Hollyer2, andJennifer L. Sullivan2Departments of 1Animal Sciences and 2Agricultural andResource EconomicsAWM-1 Composted Animal Manures CTAHR — July 19982General guidelines for attaining sanitization of com-posts that include animal manures are the following:• If composting materials are contained in a vessel andtemperatures are uniform throughout the mass ofcomposting materials, a minimum of three consecu-tive days with compost temperature above 55°C(131°F) is required to achieve sanitization.• If composting materials are in a turned pile or turnedwindrow system, the requirement is a minimum of15 days in which temperatures in the pile are above55°C and five turnings during that high-temperaturecomposting period.• The finished compost must be biologically stable sothat pathogen regrowth from the pile itself does notoccur.• Finished compost must not be reinoculated by con-taminated equipment (loaders and turning devices),by the addition of unprocessed feedstock (fresh orpartially composted animal manures), or by leachaterun-off from another pile.Temperature of a compost process can be quantita-tively measured and controlled to ensure an adequatelevel of sanitization. Although there are no federal regu-lations on composting manures, the U.S. Environmen-tal Protection Agency’s “503” regulations for biosolidscomposting provide guidelines on monitoring tempera-tures for pathogen reduction.Because a rise in temperature during composting isthe direct result of bio-oxidation activity by microbes,conditions promoting bio-oxidation should be encour-aged by careful planning and management of thecomposting process. These conditions include adequatemoisture and aeration, as well as a sufficiently low car-bon-nitrogen ratio of the aggregate raw materials of thecompost pile. The carbon-nitrogen ratio is low for ma-terials such as fresh lawn clippings and animal manures(around 20 parts carbon to 1 part nitrogen). The carbon-nitrogen ratio is high in materials such as sawdust orwood chips (where the ratio may be 400 parts carbon to1 part nitrogen). The composting process is slowed—and microbial heat generation is inhibited—by insuffi-cient amounts of materials rich in nitrogen (such as fresh,green plant materials, food scraps, or animal manures)in relation to the amounts of carbon source (such as woodchips, shredded paper, dry vegetation like straw or palmfronds, and other such organic materials high in ligninand cellulose).The finished compost product should be analyzedto determine the extent of sanitization before it is mar-keted. Laboratories use two general methods to deter-mine the pathogen content of composts, waters, andother media suspected to be sources of pathogens. Thefirst method is to search for a particular pathogen, suchas Salmonella species. Finding such a pathogen indi-cates a problem. The second method is to measure thepopulations of particular “indicator” groups of patho-gens, such as total coliforms (of which E. coli is one) orfecal streptococci. If the populations of these indicatorgroups are low, it is statistically probable that the num-bers of individual pathogens of particular concern thatare known to be associated with these groups (althoughin much smaller numbers, proportionally) is also low.Low numbers of an indicator group allows the assump-tion that the associated pathogens of particular healthconcern are not present.Pathogenic microorganismsA different group of pathogens is present in humanwastes (Table 1) than is present in animal manures (Table2). A comparison of these lists reveals the following:• Viruses that infect humans are not found in animalmanures.• Few fungal diseases of importance to humans are foundin animal manures, although some pathogenic fungifound in the environment can take up residence in ex-creted animal manures and thus get into compost.• Bacterial diseases are present in animal manures, andamong them the most important threat to humanhealth is Salmonella sp.Protozoan and helminth parasites may be present in ani-mal manures and are a potential public health problem.Infection by these organisms mainly occurs when freshanimal manures are handled. Composting greatly re-duces their numbers, although if lethal temperatures arenot reached in the process, eggs of some helminth para-sites can survive to pose a health threat. The threat ofhelminth parasites is virtually eliminated if the feces ofdogs, cats, and carnivores in general are not includedfor composting.AWM-1 Composted Animal Manures CTAHR — July 19983What happens to pathogenic microorganismsafter they leave their host?When fecal pathogens leave their host, they are exposedto the rigors of the external environment. Most patho-gens cannot survive long or reproduce outside of theirhost, but under favorable environmental conditions,there are some that can endure. Composting conditionsare not a suitable environment for pathogens and maketheir survival more difficult. Managing the conditionsof the composting process to eliminate pathogens in-volves manipulating the compost pile’s contents, mois-ture level, and oxygen supply to favor development ofdecomposing microorganisms that create an environ-ment in which it is difficult for pathogens to survive.Factors affecting the composting process as related topathogen survival are discussed in the following para-graphs.Available organic material and nutrients. The sur-vival of pathogens in animal waste depends on the avail-ability of suitable food—organic materials that they canmetabolize. Pathogenic bacteria and fungi generally canmetabolize readily available organic compounds suchas the simpler alcohols, organic acids, and sugars,whereas they generally cannot metabolize complex com-pounds such as cellulose, lignin, and humic compounds.This limitation places the pathogens present in animalmanures in an unfavorable competitive position withrespect to the nonpathogenic, decomposer microorgan-isms that are indigenous to the rest of the materials nor-mally present in a compost pile and are normally presentin far greater numbers. Pathogen metabolism and growthare thus limited by shortage of utilizable organic mate-rials and nutrients.Moisture. The moisture level in fresh animal ma-nures is usually adequate to support pathogen growth.Moisture levels suitable for composting to proceed alsoare suitable for pathogen survival. However, at mois-ture levels lower than 25 percent, all microbial growthslows and eventually ceases. If the moisture content ofcured, stabilized compost remains lower than 25 per-cent, conditions are not conducive to regrowth of patho-gens. Unfortunately, compost at such moisture levels isdifficult to use because it is too dry, and its dust maycause allergic reactions in some people. For practicaluse of finished compost, its optimum moisture contentis 40–60 percent. Therefore, manipulating the mostureTable 1.  Possible pathogens found in human waste.Pathogen DiseaseVirusEnterovirus GastroenteritisRotavirus GastroenteritisParvovirus GastroenteritisAdenovirus Respiratory infectionsHepatitis A virus Viral hepatitisPolio virus PoliomyelitisCoxsackie virus MeningitisBacteriaSalmonella (1700 serotypes) SalmonellosisShigellae ShigellosisMycobacterium tuberculosis TuberculosisVibrio cholerae CholeraEscherichia coli GastroenteritisYersinia enterocolica GastroenteritisClostridium perfringens Gastroenteritis, gangreneClostridium botulinum BotulismListeria monocytogenes EncephalitisFungiCandida sp. Mycoses (skin and systemic)Tricosporon cutaneum Skin mycosisAspergillus fumigatus Lung mycosisTrichophyton sp. Skin mycosisEpidermophyton sp. Skin mycosisMicrosporum sp. Skin mycosisProtozoaEntamoeba sp. Amoebic dysenteryGiardia lamblia GiardiasisBalantidium coli (rare) DysenteryNaegleria fowleri Primary amoebic    meningoencephalitisAcanthamoebe (rare) MeningoencephalitisHelminthsAscaris lumbricoides Human large round wormAncylostoma sp. HookwormNecator amaricanus Common hookworm of manEnterobius vermicularis Human pinwormStrongyloides stercoralis Small roundwormTrichuris trichiura Human whipwormTaenia solium Human tapewormHymenolepsis nana Dwarf tapewormAWM-1 Composted Animal Manures CTAHR — July 19984level during the composting process is not a convenientmethod for affecting pathogen survival.Temperature. The ability of pathogenic microorgan-isms to survive under high temperatures varies from onegroup to another and with the prevailing environmentalconditions. The most dangerous of the pathogens inanimal manures, such as Salmonella sp. and some sero-types of E. coli, are not thermophilic (heat-loving), donot form heat-resistant spores, and can be eliminatedby heat treatment. The threshold of heat resistance, ortolerance, of an individual type of pathogen must beTable 2.  Possible pathogens found in animal waste.Pathogen Disease HostVirus NoneBacteriaSalmonella (1700 serotypes) Salmonellosis Animals and birdsShigella sp Bacillary dysentery Nonhuman primatesEscherichia coli Gastroenteritis Many animal hostsMycobacterium sp. (very rare) Tuberculosis Cattle, via milkYersinia enterocolica (rare) Gastroenteritis Animals and poultryClostridial diseases Gastroenteritis, gangrene, botulism Normal intestinal flora and soilLeptospira interrogans*Listeria monocytogenes Encephalitis Animals, birds and soilCampylobacter (Vibrio) Gastroenteritis Cattle and sheepChlamydia psittaci Psittacosis BirdsFungiCandida sp. Mycoses (skin and systemic) Animals,birds,fruit,environmentAspergillus fumigatus Lung mycosis EnvironmentProtozoaGiardia lamblia Giardiasis Animals, esp. beaver   and muskratBalantidium coli (very rare) Dysentery Swine and primatesCryptosporidia Dysentery Animals, esp. calvesToxoplasma Toxoplasmosis CatsHelminthsAscarids (A. suum) Large round worm SwineToxocara (T.canis and T.cati) Visceral larva migrans Dogs and catsOcular larva migransAncylostoma sp. Hookworm disease Dogs and catsEchinococcus (tapeworm) Hydatid disease DogsStrongyloides stercoralis Small roundworm Dogs and cats*Leptospira interrogans is shed from the animal via the urine and may contaminate the feces. However, these organisms do not survive in dry environments nor dothey survive the composting process.surpassed for sanitation to be effective. Whether a par-ticular heat level is lethal is a function of both the tem-perature reached and the duration of exposure to thattemperature.Oxygen supply. Decomposition occurring duringcomposting is primarily the result of aerobic microor-ganisms performing biological oxidation reactions, soan adequate air supply is required. The increased tem-peratures resulting from such reactions in a compost pilecannot occur unless sufficient oxygen is available. Inthe absence of oxygen, anaerobic microorganisms areAWM-1 Composted Animal Manures CTAHR — July 19985favored, and their activities do not cause heat to be gen-erated to the extent needed for sanitation. Therefore,compost piles should be prevented from becoming toowet and should be turned to improve aeration.Microbial competition and antagonism. The num-ber of indigenous (native, or natural) microorganismsinvolved in composting is enormous. By contrast, thepopulation of pathogenic microbes in a compost pile isusually numerically small. When the conditions ofcomposting mentioned in the preceeding paragraphs areideal for decomposer microorganisms, they are less thanideal for pathogenic microorganisms. By their sheernumbers, the decomposers can effectively compete forfood sources, starving out the pathogens. Pathogens alsocan come under direct attack and be consumed by cer-tain decomposers.How are pathogens measured and monitored?To avoid the necessity of analyzing compost for all typesof pathogens, it is common to analyze for “indicator”microorganisms. Because of the wide array of patho-gens that could be present in raw animal manures, athorough analysis of a compost pile for its entire patho-gen content would be expensive. It is more practical toselect a few representative pathogens that are easy toidentify and quantify and are likely to be present in mostanimal manures. However, one of the most controver-sial aspects of the production of safe compost is the de-gree to which indicator organisms must be reduced inorder to have an adequate level of sanitization.Research has shown that counts of total coliforms,fecal streptococci, enterobacteria, certain viruses, andparasite ova can serve as indicators. For an indicatormicroorganism to be reliable, it must satisfy four re-quirements:• It must be present in sufficiently great numbers inthe raw material being composted.• It must have the same reactions to conditions (for ex-ample, the same heat-resistance threshold) as thepathogen or group of pathogens it is being used toindicate.• It must have a resistance threshold greater than thatof the targeted pathogens.• Tests for its presence and counts of its numbers mustbe simple and inexpensive.The methodology which seems to be increasingly usedby laboratories for pathogenicity evaluation of compostproducts is to test for the presence of Salmonella spe-cies, a particularly important pathogen, or to test fortwo indicator groups microorganism, total coliforms andfecal streptococci.SummaryThe possibile presence of pathogenic microorganismsin compost is a major challenge for compost producers.Composted animal manures can be used in many ben-eficial products, but they must be properly processed.By not using wastes from dogs, cats, and other carni-vores (including used bedding materials and “litter”products), a substantial part of the potential risk to hu-man health from composting animal manures can beavoided. The most important conditions with respect tosanitization are• The composting process must be thorough: all partsof the compost pile—the entire mass of organic ma-terials—must be exposed to temperatures of 55°C(131°F) or more and maintained at that level for atleast three days.• The composting process must be complete: finishedcompost is biologically stable and no longer condu-cive to the growth of pathogens.• The finished compost must not be reinoculated withpathogens.ReferencesBell, J.C., S.R. Palmer. and J.M. Payne. 1988. TheZoonoses. Infections transmitted from animals toman. Edward Arnold, London, UK. 241 p.Bertoldi, M., F. Zucconi, and M. Civilini. 1988. Tem-perature, pathogen control and product quality.BioCycle. February, 1988. p. 43–50.Composting Council. 1996. The compost enhancementguide. Alexandria, VA.Hawaii Department of Health. 1996. Guidelines for live-stock waste management. Honolulu, HI.Rynk, Robert (ed). 1992. On-farm composting hand-book. Northeast Regional Agricultural EngineeringService, Ithaca, NY.This and many other CTAHR publications can be found on the college’s website at <www.ctahr.hawaii.edu>

Composted Animal Manures: Precautions and Processing

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Composted Animal Manures: Precautions and Processing

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