compost

File:Composting in the Escuela Barreales.jpg

File:Compost bins at the Evergreen State College Organic Farm during mid June of 2019.jpg organic farm in Washington]]

File:Compost pile.JPG

File:Food-scraps-compost.jpg

Composting is an aerobic method of decomposing organic solid wastes,{{Cite book|url=https://books.google.com/books?id=3BhSAAAAMAAJ&q=Human+waste+can+also+be+added+as+an+input+to+the+composting+process+since+human+waste+is+a+nitrogen-rich+organic+material|title=Introduction to Environmental Engineering and Science|last=Masters|first=Gilbert M.|date=1997|publisher=Prentice Hall|isbn=9780131553842|language=en|access-date=28 June 2017|archive-date=26 January 2021|archive-url=https://web.archive.org/web/20210126005451/https://books.google.com/books?id=3BhSAAAAMAAJ&q=Human+waste+can+also+be+added+as+an+input+to+the+composting+process+since+human+waste+is+a+nitrogen-rich+organic+material|url-status=live}} so it can be used to recycle organic material. The process involves decomposing organic material into a humus-like material, known as compost, which is a good fertilizer for plants.

Composting organisms require four equally important ingredients to work effectively:

• Carbon is needed for energy; the microbial oxidation of carbon produces the heat required for other parts of the composting process. High carbon materials tend to be brown and dry.
• Nitrogen is needed to grow and reproduce more organisms to oxidize the carbon. High nitrogen materials tend to be green and wet. They can also include colourful fruits and vegetables.
• Oxygen is required for oxidizing the carbon, the decomposition process. Aerobic bacteria need oxygen levels above 5% to perform the processes needed for composting.
• Water is necessary in the right amounts to maintain activity without causing locally anaerobic conditions.

Certain ratios of these materials allow microorganisms to work at a rate that will heat up the compost pile. Active management of the pile (e.g., turning over the compost heap) is needed to maintain sufficient oxygen and the right moisture level. The air/water balance is critical to maintaining high temperatures {{convert|130–160|F}} until the materials are broken down.{{Cite journal|last=Lal|first=Rattan|date=2003-11-30|title=Composting|url=http://link.galegroup.com/apps/doc/CX3408100055/GVRL?sid=GVRL&xid=54515a57|journal=Pollution a to Z|language=en|volume=1|access-date=17 August 2019|archive-date=13 July 2021|archive-url=https://web.archive.org/web/20210713211357/https://galeapps.gale.com/apps/auth?userGroupName=&sid=GVRL&origURL=https%3A%2F%2Fgo.gale.com%2Fps%2Fi.do%3Fp%3DGVRL%26u%3D%26id%3DGALE%7CCX3408100055%26v%3D2.1%26it%3Dr%26sid%3DGVRL%26asid%3D54515a57&prodId=GVRL|url-status=live}}

Composting is most efficient with a carbon-to-nitrogen ratio of about 25:1.{{cite book|url=http://www.eawag.ch/en/department/sandec/publications/compendium/|title=Compendium of Sanitation Systems and Technologies|last1=Tilley|first1=Elizabeth|last2=Ulrich|first2=Lukas|last3=Lüthi|first3=Christoph|last4=Reymond|first4=Philippe|last5=Zurbrügg|first5=Chris|publisher=Swiss Federal Institute of Aquatic Science and Technology (Eawag)|year=2014|isbn=978-3-906484-57-0|edition=2nd|location=Duebendorf, Switzerland|chapter=Septic tanks|chapter-url=http://ecompendium.sswm.info/sanitation-technologies/septic-tank?group_code=s|access-date=1 April 2018|archive-date=22 October 2019|archive-url=https://web.archive.org/web/20191022044558/https://www.eawag.ch/en/department/sandec/publications/compendium/|url-status=live}} Hot composting focuses on retaining heat to increase the decomposition rate, thus producing compost more quickly. Rapid composting is favored by having a carbon-to-nitrogen ratio of about 30 carbon units or less. Above 30, the substrate is nitrogen starved. Below 15, it is likely to outgas a portion of nitrogen as ammonia.{{cite book|last1=Haug|first1=Roger|title=The Practical Handbook of Compost Engineering|url=https://books.google.com/books?id=MX_jbemODmAC&q=ammonium+phosphate+compost&pg=PA249|publisher=CRC Press|isbn=9780873713733|year=1993|access-date=16 October 2020|archive-date=13 July 2021|archive-url=https://web.archive.org/web/20210713211319/https://books.google.com/books?id=MX_jbemODmAC&q=ammonium+phosphate+compost&pg=PA249|url-status=live}}

Nearly all dead plant and animal materials have both carbon and nitrogen in different amounts.{{Cite web|url=http://www.klickitatcounty.org/SolidWaste/fileshtml/organics/compostCalc.htm|archiveurl=https://web.archive.org/web/20111117112037/http://www.klickitatcounty.org/solidwaste/fileshtml/organics/compostCalc.htm|url-status=dead|title=Klickitat County WA, USA Compost Mix Calculator|archivedate=17 November 2011}} Fresh grass clippings have an average ratio of about 15:1 and dry autumn leaves about 50:1 depending upon species. Composting is an ongoing and dynamic process; adding new sources of carbon and nitrogen consistently, as well as active management, is important.

Organisms can break down organic matter in compost if provided with the correct mixture of water, oxygen, carbon, and nitrogen. They fall into two broad categories: chemical decomposers, which perform chemical processes on the organic waste, and physical decomposers, which process the waste into smaller pieces through methods such as grinding, tearing, chewing, and digesting.

• Bacteria are the most abundant and important of all the microorganisms found in compost. Bacteria process carbon and nitrogen and excrete plant-available nutrients such as nitrogen, phosphorus, and magnesium. Depending on the phase of composting, mesophilic or thermophilic bacteria may be the most prominent.
• Mesophilic bacteria get compost to the thermophilic stage through oxidation of organic material. Afterwards they cure it, which makes the fresh compost more bioavailable for plants.{{Cite web|title=Compost Physics - Cornell Composting|url=http://compost.css.cornell.edu/physics.html#:~:text=Compost%20heat%20is%20produced%20as,microbial%20breakdown%20of%20organic%20material.&text=Compost%20managers%20strive%20to%20keep,help%20to%20dissipate%20the%20heat.|access-date=2021-04-11|website=compost.css.cornell.edu|archive-date=9 November 2020|archive-url=https://web.archive.org/web/20201109215044/http://compost.css.cornell.edu/physics.html#:~:text=Compost%20heat%20is%20produced%20as,microbial%20breakdown%20of%20organic%20material.&text=Compost%20managers%20strive%20to%20keep,help%20to%20dissipate%20the%20heat.|url-status=live}}
• Thermophilic bacteria do not reproduce and are not active between {{cvt|-5|and|25|C}},{{Cite journal|last1=Marchant|first1=Roger|last2=Franzetti|first2=Andrea|last3=Pavlostathis|first3=Spyros G.|last4=Tas|first4=Didem Okutman|last5=Erdbrűgger|first5=Isabel|last6=Űnyayar|first6=Ali|last7=Mazmanci|first7=Mehmet A.|last8=Banat|first8=Ibrahim M.|date=2008-04-01|title=Thermophilic bacteria in cool temperate soils: are they metabolically active or continually added by global atmospheric transport?|url=https://doi.org/10.1007/s00253-008-1372-y|journal=Applied Microbiology and Biotechnology|language=en|volume=78|issue=5|pages=841–852|doi=10.1007/s00253-008-1372-y|pmid=18256821|s2cid=24884198|issn=1432-0614|access-date=29 April 2021|archive-date=13 July 2021|archive-url=https://web.archive.org/web/20210713211321/https://link.springer.com/article/10.1007/s00253-008-1372-y|url-status=live}} yet are found throughout soil. They activate once the mesophilic bacteria have begun to break down organic matter and increase the temperature to their optimal range. They have been shown to enter soils via rainwater. They are present so broadly because of many factors, including their spores being resilient.{{Cite journal|last=Zeigler|first=Daniel R.|date=January 2014|title=The Geobacillus paradox: why is a thermophilic bacterial genus so prevalent on a mesophilic planet?|journal=Microbiology|volume=160|issue=Pt 1|pages=1–11|doi=10.1099/mic.0.071696-0|doi-access=free |issn=1465-2080|pmid=24085838}} Thermophilic bacteria thrive at higher temperatures, reaching {{cvt|40|–|60|C}} in typical mixes. Large-scale composting operations, such as windrow composting, may exceed this temperature, potentially killing beneficial soil microorganisms but also pasteurizing the waste.
• Actinomycetota are needed to break down paper products such as newspaper, bark, etc., and other large molecules such as lignin and cellulose that are more difficult to decompose. The "pleasant, earthy smell of compost" is attributed to Actinomycetota. They make carbon, ammonia, and nitrogen nutrients available to plants.
• Fungi such as molds and yeasts help break down materials that bacteria cannot, especially cellulose and lignin in woody material.
• Protozoa contribute to biodegradation of organic matter and consume inactive bacteria, fungi, and micro-organic particulates.{{Cite web|last1=Trautmann|first1=Nancy|last2=Olynciw|first2=Elaina|title=Compost Microorganisms|url=http://compost.css.cornell.edu/microorg.html|url-status=live|access-date=2021-07-12|website=CORNELL Composting|publisher=Cornell Waste Management Institute|archive-date=15 November 2019|archive-url=https://web.archive.org/web/20191115202006/http://compost.css.cornell.edu/microorg.html}}

• Ants create nests, making the soil more porous and transporting nutrients to different areas of the compost.
• Beetles as grubs feed on decaying vegetables.
• Earthworms ingest partly composted material and excrete worm castings, making nitrogen, calcium, phosphorus, and magnesium available to plants. The tunnels they create as they move through the compost also increase aeration and drainage.
• Flies feed on almost all organic material and put bacteria into the compost. Their population is kept in check by mites and the thermophilic temperatures that are unsuitable for fly larvae.
• Millipedes break down plant material.
• Rotifers feed on plant particles.
• Snails and slugs feed on living or fresh plant material. They should be removed from compost before use, as they can damage plants and crops.
• Sow bugs feed on rotting wood and decaying vegetation.
• Springtails feed on fungi, molds, and decomposing plants.

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Under ideal conditions, composting proceeds through three major phases:{{Cite web |title=Phases of composting |url=https://compostsegria.com/ca/en/fases-del-compostaje/ |access-date=2025-02-14 |website=Compost Segrià |language=en-GB}}

1. Mesophilic phase: The initial, mesophilic phase is when the decomposition is carried out under moderate temperatures by mesophilic microorganisms. 2 to 8 days
2. Thermophilic phase: As the temperature rises, a second, thermophilic phase starts, in which various thermophilic bacteria carry out the decomposition under higher temperatures ({{convert|50|to|60|C}}.)
3. Cooling phase (also called Mesophilic II)
4. Maturation phase: As the supply of high-energy compounds dwindles, the temperature starts to decrease.

Semicomposting is the degradation process that handles volumes of organic waste lower than that recommended for composting and therefore does not present a thermophilic stage, because mesophilic microorganisms are the only responsible ones, for the degradation of organic matter.* [https://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-58392017000300287#B11 Comparison of three systems of decomposition of agricultural residues for the production of organic fertilizers. Chilean J. Agric. Res. vol.77 no.3 Chillán set. 2017.][https://www.redalyc.org/journal/339/33953499012/html/ SEMICOMPOST AND VERMICOMPOST MIXED WITH PEAT MOSS ENHANCE SEED GERMINATION AND DEVELOPMENT OF LETTUCE AND TOMATO SEEDLINGS, Interciencia, vol. 42, no. 11, pp. 774-779, 2017]

The time required to compost material relates to the volume of material, the particle size of the inputs (e.g. wood chips break down faster than branches), and the amount of mixing and aeration. Generally, larger piles reach higher temperatures and remain in a thermophilic stage for days or weeks. This is hot composting and is the usual method for large-scale municipal facilities and agricultural operations.

The Berkeley method produces finished compost in 18 days. It requires assembly of at least {{convert|1|m3}} of material at the outset and needs turning every two days after an initial four-day phase.{{cite web|url=http://vric.ucdavis.edu/pdf/compost_rapidcompost.pdf|title=The Rapid Compost Method by Robert Raabe, Professor of Plant Pathology, Berkeley|access-date=21 December 2017|archive-date=15 December 2017|archive-url=https://web.archive.org/web/20171215190533/http://vric.ucdavis.edu/pdf/compost_rapidcompost.pdf|url-status=live}} Such short processes involve some changes to traditional methods, including smaller, more homogenized particle sizes in the input materials, controlling carbon-to-nitrogen ratio (C:N) at 30:1 or less, and careful monitoring of the moisture level.

Cold composting is a slower process that can take up to a year to complete.{{cite web |title=Composting |url=https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs144p2_014870.pdf |publisher=USDA Natural Resources Conservation Service |access-date=30 December 2020 |date=April 1998 |archive-date=6 May 2021 |archive-url=https://web.archive.org/web/20210506090827/https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs144p2_014870.pdf |url-status=live }} It results from smaller piles, including many residential compost piles that receive small amounts of kitchen and garden waste over extended periods. Piles smaller than {{convert|1|m3}} tend not to reach and maintain high temperatures.{{cite web |title=Home Composting |url=https://ecommons.cornell.edu/bitstream/handle/1813/44638/compostbrochure.pdf?sequence=2&isAllowed=y |publisher=Cornell Waste Management Institute |access-date=30 December 2020 |date=2005 |archive-date=16 October 2020 |archive-url=https://web.archive.org/web/20201016191518/https://ecommons.cornell.edu/bitstream/handle/1813/44638/compostbrochure.pdf?sequence=2&isAllowed=y |url-status=live }} Turning is not necessary with cold composting, although a risk exists that parts of the pile may go anaerobic as it becomes compacted or waterlogged.

Composting can destroy some pathogens and seeds, by reaching temperatures above {{convert|50|C}}.{{Cite web|last=Robert|first=Graves|date=February 2000|title=Composting|url=https://www.wcc.nrcs.usda.gov/ftpref/wntsc/AWM/neh637c2.pdf|website=Environmental Engineering National Engineering Handbook|pages=2–22|access-date=19 October 2020|archive-date=15 January 2021|archive-url=https://web.archive.org/web/20210115060905/https://www.wcc.nrcs.usda.gov/ftpref/wntsc/AWM/neh637c2.pdf|url-status=live}}

Dealing with stabilized compost – i.e. composted material in which microorganisms have finished digesting the organic matter and the temperature has reached between {{cvt|50|and|70|C}} – poses very little risk, as these temperatures kill pathogens and even make oocysts unviable.{{Cite journal|date=1995-08-01|title=Occurrence of enteric pathogens in composted domestic solid waste containing disposable diapers|url=https://www.sciencedirect.com/science/article/abs/pii/S0734242X95900810|journal=Waste Management & Research|language=en|volume=13|issue=4|pages=315–324|doi=10.1016/S0734-242X(95)90081-0|issn=0734-242X|access-date=19 April 2021|archive-date=19 April 2021|archive-url=https://web.archive.org/web/20210419114736/https://www.sciencedirect.com/science/article/abs/pii/S0734242X95900810|url-status=live|last1=Gerba|first1=C.|bibcode=1995WMR....13..315G }} The temperature at which a pathogen dies depends on the pathogen, how long the temperature is maintained (seconds to weeks), and pH.{{Cite journal|last1=Mehl|first1=Jessica|last2=Kaiser|first2=Josephine|last3=Hurtado|first3=Daniel|last4=Gibson|first4=Daragh A.|last5=Izurieta|first5=Ricardo|last6=Mihelcic|first6=James R.|date=2011-02-03|title=Pathogen destruction and solids decomposition in composting latrines: study of fundamental mechanisms and user operation in rural Panama|journal=Journal of Water and Health|volume=9|issue=1|pages=187–199|doi=10.2166/wh.2010.138|pmid=21301126|issn=1477-8920|doi-access=free|bibcode=2011JWH.....9..187M }}

Compost products such as compost tea and compost extracts have been found to have an inhibitory effect on Fusarium oxysporum, Rhizoctonia species, and Pythium debaryanum, plant pathogens that can cause crop diseases.{{Cite journal|last1=Milinković|first1=Mira|last2=Lalević|first2=Blažo|last3=Jovičić-Petrović|first3=Jelena|last4=Golubović-Ćurguz|first4=Vesna|last5=Kljujev|first5=Igor|last6=Raičević|first6=Vera|date=January 2019|title=Biopotential of compost and compost products derived from horticultural waste—Effect on plant growth and plant pathogens' suppression|url=http://dx.doi.org/10.1016/j.psep.2018.09.024|journal=Process Safety and Environmental Protection|volume=121|pages=299–306|doi=10.1016/j.psep.2018.09.024|bibcode=2019PSEP..121..299M |s2cid=104755582|issn=0957-5820|access-date=27 April 2021|archive-date=13 July 2021|archive-url=https://web.archive.org/web/20210713211321/https://linkinghub.elsevier.com/retrieve/pii/S0957582018309704|url-status=live}} Aerated compost teas are more effective than compost extracts. The microbiota and enzymes present in compost extracts also have a suppressive effect on fungal plant pathogens.{{Cite journal|last1=El-Masry|first1=M.H.|last2=Khalil|first2=A.I.|last3=Hassouna|first3=M.S.|last4=Ibrahim|first4=H.A.H.|date=2002-08-01|title=In situ and in vitro suppressive effect of agricultural composts and their water extracts on some phytopathogenic fungi|url=https://doi.org/10.1023/A:1016302729218|journal=World Journal of Microbiology and Biotechnology|language=en|volume=18|issue=6|pages=551–558|doi=10.1023/A:1016302729218|s2cid=81831444|issn=1573-0972|access-date=27 April 2021|archive-date=13 July 2021|archive-url=https://web.archive.org/web/20210713211358/https://link.springer.com/article/10.1023/A:1016302729218|url-status=live}} Compost is a good source of biocontrol agents like B. subtilis, B. licheniformis, and P. chrysogenum that fight plant pathogens. Sterilizing the compost, compost tea, or compost extracts reduces the effect of pathogen suppression.

When turning compost that has not gone through phases where temperatures above {{cvt|50|C}} are reached, a mouth mask and gloves must be worn to protect from diseases that can be contracted from handling compost, including:{{Cite web|title=Compost Pile Hazards|url=https://www.nachi.org/compost-pile-hazards.htm|access-date=2021-04-19|website=www.nachi.org|language=en|archive-date=19 April 2021|archive-url=https://web.archive.org/web/20210419120553/https://www.nachi.org/compost-pile-hazards.htm|url-status=live}}

• Aspergillosis
• Farmer's lung
• Histoplasmosis – a fungus that grows in guano and bird droppings
• Legionnaires' disease
• Paronychia – via infection around the fingernails and toenails
• Tetanus – a central nervous system disease

Oocytes are rendered unviable by temperatures over {{cvt|50|C}}.

Compost adds organic matter to the soil and increases the nutrient content and biodiversity of microbes in soil.{{Cite web |last=US EPA |first=OLEM |date=2015-08-12 |title=Composting |url=https://www.epa.gov/sustainable-management-food/composting |access-date=2024-05-18 |website=www.epa.gov |language=en}} Composting at home reduces the amount of green waste being hauled to dumps or composting facilities. The reduced volume of materials being picked up by trucks results in fewer trips, which in turn lowers the overall emissions from the waste-management fleet.

Potential sources of compostable materials, or feedstocks, include residential, agricultural, and commercial waste streams. Residential food or yard waste can be composted at home,{{cite web|title=Composting for the Homeowner - University of Illinois Extension|url=http://web.extension.illinois.edu/homecompost/science.cfm|url-status=dead|archive-url=https://web.archive.org/web/20160217221013/http://web.extension.illinois.edu/homecompost/science.cfm|archive-date=17 February 2016|access-date=12 July 2021|website=Composting for the Homeowner|publisher=University of Illinois Board of Trustees}} or collected for inclusion in a large-scale municipal composting facility. In some regions, it could also be included in a local or neighborhood composting project.{{cite news |last1=Nierenberg |first1=Amelia |title=Composting Has Been Scrapped. These New Yorkers Picked Up the Slack. |url=https://www.nytimes.com/2020/08/09/nyregion/nyc-compost-recycling.html |access-date=17 November 2020 |work=The New York Times |date=9 August 2020 |archive-date=25 November 2020 |archive-url=https://web.archive.org/web/20201125032441/https://www.nytimes.com/2020/08/09/nyregion/nyc-compost-recycling.html |url-status=live }}{{cite web|title=STA Feedstocks|url=https://www.compostingcouncil.org/page/STA-Feedstocks|website=U.S. Composting Council|access-date=17 November 2020|archive-date=27 October 2020|archive-url=https://web.archive.org/web/20201027064105/https://www.compostingcouncil.org/page/STA-Feedstocks|url-status=dead}}

{{Main|Biodegradable waste}}

File:Spontaneous combustion of compost pile.jpg microorganisms.]]

The two broad categories of organic solid waste are green and brown. Green waste is generally considered a source of nitrogen and includes pre- and post-consumer food waste, grass clippings, garden trimmings, and fresh leaves. Animal carcasses, roadkill, and butcher residue can also be composted, and these are considered nitrogen sources.{{cite web |title=Natural Rendering: Composting Livestock Mortality and Butcher Waste |url=https://ecommons.cornell.edu/bitstream/handle/1813/2149/naturalrenderingFS.pdf?sequence=19&isAllowed=y |publisher=Cornell Waste Management Institute |access-date=17 November 2020 |date=2002 |archive-date=24 February 2021 |archive-url=https://web.archive.org/web/20210224214513/https://ecommons.cornell.edu/bitstream/handle/1813/2149/naturalrenderingFS.pdf?sequence=19&isAllowed=y |url-status=live }}

Brown waste is a carbon source. Typical examples are dried vegetation and woody material such as fallen leaves, straw, woodchips, limbs, logs, pine needles, sawdust, and wood ash, but not charcoal ash.{{cite web |last1=Rishell |first1=Ed |title=Backyard Composting |url=https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/HORT/HORT-49/HORT-49-PDF.pdf |website=Virginia Cooperative Extension |publisher=Virginia Polytechnic Institute and State University |access-date=17 November 2020 |archive-url=https://web.archive.org/web/20180920170413/http://pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/HORT/HORT-49/HORT-49-PDF.pdf |archive-date=20 September 2018 |date=2013}} Products derived from wood such as paper and plain cardboard are also considered carbon sources.

On many farms, the basic composting ingredients are animal manure generated on the farm as a nitrogen source, and bedding as the carbon source. Straw and sawdust are common bedding materials. Nontraditional bedding materials are also used, including newspaper and chopped cardboard. The amount of manure composted on a livestock farm is often determined by cleaning schedules, land availability, and weather conditions. Each type of manure has its own physical, chemical, and biological characteristics. Cattle and horse manures, when mixed with bedding, possess good qualities for composting. Swine manure, which is very wet and usually not mixed with bedding material, must be mixed with straw or similar raw materials. Poultry manure must be blended with high-carbon, low-nitrogen materials.Dougherty, Mark. (1999). Field Guide to On-Farm Composting. Ithaca, New York: Natural Resource, Agriculture, and Engineering Service.

{{Further|Reuse of excreta}}

Human excreta, sometimes called "humanure" in the composting context,{{cite web |url=https://modernfarmer.com/2017/03/humanure-next-frontier-composting/ |title=Humanure: The Next Frontier in Composting |first=Brian |last=Barth |work=Modern Farmer |date=7 March 2017 |access-date=23 March 2022 |archive-date=21 May 2022 |archive-url=https://web.archive.org/web/20220521095117/https://modernfarmer.com/2017/03/humanure-next-frontier-composting/ |url-status=dead }}{{cite web |url=https://www.theguardian.com/environment/2009/may/12/humanure-composting-toilets |title=Humanure: the end of sewage as we know it? |via=The Guardian |work=Grist |date=12 May 2009}} can be added as an input to the composting process since it is a nutrient-rich organic material. Nitrogen, which serves as a building block for important plant amino acids, is found in solid human waste.{{Cite web |title=Nitrogen in the Plant |url=https://extension.missouri.edu/publications/wq259 |access-date=2023-01-12 |website=extension.missouri.edu |language=en}}{{Cite web |date=2020-06-02 |title=Human waste could be used to create nitrogen-rich fertilizer |url=https://www.news-medical.net/news/20200602/Human-waste-could-be-used-to-create-nitrogen-rich-fertilizer.aspx |access-date=2023-01-12 |website=News-Medical.net |language=en}} Phosphorus, which helps plants convert sunlight into energy in the form of ATP, can be found in liquid human waste.{{Cite web |title=Phosphate in Urine |url=https://wa.kaiserpermanente.org/kbase/topic.jhtml?docId=hw202342 |access-date=2023-01-12 |website=wa.kaiserpermanente.org}}{{Cite web |title=Phosphorus Basics: Deficiency Symptoms, Sufficiency Ranges, and Common Sources |url=https://www.aces.edu/blog/topics/crop-production/phosphorus-basics-deficiency-symptoms-sufficiency-ranges-and-common-sources/ |access-date=2023-01-12 |website=Alabama Cooperative Extension System |language=en-US}}

Solid human waste can be collected directly in composting toilets, or indirectly in the form of sewage sludge after it has undergone treatment in a sewage treatment plant. Both processes require capable design, as potential health risks need to be managed. In the case of home composting, a wide range of microorganisms, including bacteria, viruses, and parasitic worms, can be present in feces, and improper processing can pose significant health risks.{{cite journal|title=Domestic waste composting facilities: a review of human health risks.|journal = Environment International|volume = 35|issue = 2|pages = 382–9|date = August 2012|pmid = 18701167|last1 = Domingo|first1 = J. L.|last2 = Nadal|first2 = M.|doi = 10.1016/j.envint.2008.07.004}} In the case of large sewage treatment facilities that collect wastewater from a range of residential, commercial and industrial sources, there are additional considerations. The composted sewage sludge, referred to as biosolids, can be contaminated with a variety of metals and pharmaceutical compounds.{{cite journal |last1=Kinney |first1=Chad A. |last2=Furlong |first2=Edward T. |last3=Zaugg |first3=Steven D. |last4=Burkhardt |first4=Mark R. |last5=Werner |first5=Stephen L. |last6=Cahill |first6=Jeffery D. |last7=Jorgensen |first7=Gretchen R. |title=Survey of Organic Wastewater Contaminants in Biosolids Destined for Land Application † |journal=Environmental Science & Technology |date=December 2006 |volume=40 |issue=23 |pages=7207–7215 |doi=10.1021/es0603406 |pmid=17180968 |bibcode=2006EnST...40.7207K |url=https://pubs.acs.org/doi/10.1021/es0603406 |access-date=2 January 2021 |archive-date=14 April 2021 |archive-url=https://web.archive.org/web/20210414130639/https://pubs.acs.org/doi/10.1021/es0603406 |url-status=live }}{{cite journal |last1=Morera |first1=M T |last2=Echeverría |first2=J. |last3=Garrido |first3=J. |title=Bioavailability of heavy metals in soils amended with sewage sludge |journal=Canadian Journal of Soil Science |date=1 November 2002 |volume=82 |issue=4 |pages=433–438 |doi=10.4141/S01-072 |bibcode=2002CaJSS..82..433M |url=https://cdnsciencepub.com/doi/abs/10.4141/S01-072 |access-date=2 January 2021 |hdl=2454/10748 |hdl-access=free |archive-date=13 July 2021 |archive-url=https://web.archive.org/web/20210713211355/https://cdnsciencepub.com/doi/abs/10.4141/S01-072 |url-status=live }} Insufficient processing of biosolids can also lead to problems when the material is applied to land.{{cite news |title='Humanure' dumping sickens homeowner |url=https://www.insideottawavalley.com/community-story/3800586--humanure-dumping-sickens-homeowner/ |access-date=2 January 2021 |publisher=Renfrew Mercury |date=13 October 2011 |archive-url=https://web.archive.org/web/20151110103646/https://www.insideottawavalley.com/community-story/3800586--humanure-dumping-sickens-homeowner/ |archive-date=10 November 2015}}

Urine can be put on compost piles or directly used as fertilizer.{{Cite web |url=http://esa.un.org/iys/docs/san_lib_docs/ESR2web%5B1%5D.pdf |title=Stockholm Environment Institute - EcoSanRes - Guidelines on the Use of Urine and Feces in Crop Production |access-date=14 July 2010 |archive-url=https://web.archive.org/web/20101230041356/http://esa.un.org/iys/docs/san_lib_docs/ESR2web%5b1%5d.pdf |archive-date=30 December 2010 |url-status=dead }} Adding urine to compost can increase temperatures, so can increase its ability to destroy pathogens and unwanted seeds. Unlike feces, urine does not attract disease-spreading flies (such as houseflies or blowflies), and it does not contain the most hardy of pathogens, such as parasitic worm eggs.{{cite journal |last1=Trimmer |first1=J.T. |last2=Margenot |first2=A.J. |last3=Cusick |first3=R.D. |last4=Guest |first4=J.S. |title=Aligning Product Chemistry and Soil Context for Agronomic Reuse of Human-Derived Resources |journal=Environmental Science and Technology |date=2019 |volume=53 |issue=11 |pages=6501–6510|doi=10.1021/acs.est.9b00504 |pmid=31017776 |bibcode=2019EnST...53.6501T |s2cid=131775180 }}

Animal carcasses may be composted as a disposal option. Such material is rich in nitrogen.{{cite web |title=Composting Large Animal Carcasses |url=https://tammi.tamu.edu/2017/07/20/composting-large-animal-carcasses/ |website=Texas Animal Manure Management Issues |date=20 July 2017}}

{{excerpt|Human composting}}

File:ComposterRollingDesign.jpg

{{excerpt|in-vessel composting|paragraphs=1–2}}

{{excerpt|aerated static pile composting|paragraphs=1–2}}

{{excerpt|windrow composting|paragraphs=1–2}}

File:End point (4315712587).jpg

{{Main|Hügelkultur}}

The practice of making raised garden beds or mounds filled with rotting wood is also called {{lang|de|Hügelkultur}} in German.{{cite web |url=http://www.richsoil.com/hugelkultur/ |title=hugelkultur: the ultimate raised garden beds |publisher=Richsoil.com |date=2007-07-27 |access-date=2013-07-18 |archive-date=7 January 2018 |archive-url=https://web.archive.org/web/20180107013815/https://richsoil.com/hugelkultur/ |url-status=live }}{{cite web |url=http://permaculture.org.au/2010/08/03/the-art-and-science-of-making-a-hugelkultur-bed-transforming-woody-debris-into-a-garden-resource/ |title=The Art and Science of Making a Hugelkultur Bed - Transforming Woody Debris into a Garden Resource Permaculture Research Institute - Permaculture Forums, Courses, Information & News |date=2010-08-03 |access-date=2013-07-18 |archive-url=https://web.archive.org/web/20151105061510/http://permaculture.org.au/2010/08/03/the-art-and-science-of-making-a-hugelkultur-bed-transforming-woody-debris-into-a-garden-resource/ |archive-date=5 November 2015 |url-status=dead }} It is in effect creating a nurse log that is covered with soil.

Benefits of Hügelkultur garden beds include water retention and warming of soil.{{cite web |url=http://permaculture.org.au/2012/01/04/hugelkultur-composting-whole-trees-with-ease/#more-6825 |title=Hugelkultur: Composting Whole Trees With Ease Permaculture Research Institute - Permaculture Forums, Courses, Information & News |date=2012-01-04 |access-date=2013-07-18 |archive-url=https://web.archive.org/web/20150928110713/http://permaculture.org.au/2012/01/04/hugelkultur-composting-whole-trees-with-ease/#more-6825 |archive-date=28 September 2015 |url-status=dead }} Buried wood acts like a sponge as it decomposes, able to capture water and store it for later use by crops planted on top of the bed.Hemenway, Toby (2009). Gaia's Garden: A Guide to Home-Scale Permaculture. Chelsea Green Publishing. pp. 84–85. {{ISBN|978-1-60358-029-8}}.

{{excerpt|Composting toilet|paragraphs=1-3}}

• Vermicompost (also called worm castings, worm humus, worm manure, or worm faeces) is the end product of the breakdown of organic matter by earthworms.{{cite web |url=http://southwoodsforestgardens.blogspot.com/2009/01/paper-on-invasive-european-worms.html |title=Paper on Invasive European Worms |date=21 January 2009 |access-date=2009-02-22 |archive-date=9 October 2019 |archive-url=https://web.archive.org/web/20191009124334/https://southwoodsforestgardens.blogspot.com/2009/01/paper-on-invasive-european-worms.html |url-status=live }} These castings have been shown to contain reduced levels of contaminants and a higher saturation of nutrients than the organic materials before vermicomposting.{{cite journal | author1 = Ndegwa, P.M. | author2 = Thompson, S.A. | author3 = Das, K.C. | title = Effects of stocking density and feeding rate on vermicomposting of biosolids | journal = Bioresource Technology | volume = 71 | pages = 5–12 | year = 1998 | doi = 10.1016/S0960-8524(99)00055-3 | url = http://www.earthworm.co.za/wp-content/uploads/2009/04/effect-of-stocking-density-feeding-rate-on-vermicomposting-of-biosolids.pdf | access-date = 15 February 2021 | archive-date = 8 August 2017 | archive-url = https://web.archive.org/web/20170808071348/http://www.earthworm.co.za/wp-content/uploads/2009/04/effect-of-stocking-density-feeding-rate-on-vermicomposting-of-biosolids.pdf | url-status = live }}
• Black soldier fly (Hermetia illucens) larvae are able to rapidly consume large amounts of organic material and can be used to treat human waste. The resulting compost still contains nutrients and can be used for biogas production, or further traditional composting or vermicomposting{{Cite journal|last1=Lalander|first1=Cecilia|last2=Nordberg|first2=Åke|last3=Vinnerås|first3=Björn|title=A comparison in product-value potential in four treatment strategies for food waste and faeces – assessing composting, fly larvae composting and anaerobic digestion|journal=GCB Bioenergy|volume=10|issue=2|language=en|pages=84–91|doi=10.1111/gcbb.12470|issn=1757-1707|year=2018|doi-access=free|bibcode=2018GCBBi..10...84L }}{{Cite journal|last1=Banks|first1=Ian J.|last2=Gibson|first2=Walter T.|last3=Cameron|first3=Mary M.|author-link3=Mary Cameron (entomologist)|date=2014-01-01|title=Growth rates of black soldier fly larvae fed on fresh human faeces and their implication for improving sanitation|journal=Tropical Medicine & International Health|language=en|volume=19|issue=1|pages=14–22|doi=10.1111/tmi.12228|pmid=24261901|s2cid=899081|issn=1365-3156|doi-access=free}}
• Bokashi is a fermentation process rather than a decomposition process, and so retains the feedstock's energy, nutrient and carbon contents. There must be sufficient carbohydrate for fermentation to complete and therefore the process is typically applied to food waste, including noncompostable items. Carbohydrate is transformed into lactic acid, which dissociates naturally to form lactate, a biological energy carrier. The preserved result is therefore readily consumed by soil microbes and from there by the entire soil food web, leading to a significant increase in soil organic carbon and turbation. The process completes in weeks and returns soil acidity to normal.
• Co-composting is a technique that processes organic solid waste together with other input materials such as dewatered fecal sludge or sewage sludge.
• Anaerobic digestion combined with mechanical sorting of mixed waste streams is increasingly being used in developed countries due to regulations controlling the amount of organic matter allowed in landfills. Treating biodegradable waste before it enters a landfill reduces global warming from fugitive methane; untreated waste breaks down anaerobically in a landfill, producing landfill gas that contains methane, a potent greenhouse gas. The methane produced in an anaerobic digester can be used as biogas.{{Cite web|url=https://www.politico.com/news/magazine/2019/11/21/food-waste-fuel-energy-sustainability-070265|title=How Cities Are Turning Food into Fuel|last=Dawson|first=Lj|website=POLITICO|date=21 November 2019 |language=en|access-date=2020-02-28|archive-date=28 February 2020|archive-url=https://web.archive.org/web/20200228203453/https://www.politico.com/news/magazine/2019/11/21/food-waste-fuel-energy-sustainability-070265|url-status=live}}

File:Compost steaming - detail 3.jpg

On open ground for growing wheat, corn, soybeans, and similar crops, compost can be broadcast across the top of the soil using spreader trucks or spreaders pulled behind a tractor. It is expected that the spread layer is very thin (approximately {{cvt|6|mm}}) and worked into the soil prior to planting. Application rates of {{cvt|25|mm}} or more are not unusual when trying to rebuild poor soils or control erosion. Due to the extremely high cost of compost per unit of nutrients in the United States, on-farm use is relatively rare since rates over 4 tons/acre may not be affordable. This results from an over-emphasis on "recycling organic matter" than on "sustainable nutrients." In countries such as Germany, where compost distribution and spreading are partially subsidized in the original waste fees, compost is used more frequently on open ground on the premise of nutrient "sustainability".{{Cite web|url = http://www.landwirtschaft-mlr.baden-wuerttemberg.de/servlet/PB/show/1118971/Landinfo_Nachhaltige%20Kompostanwendung%20in%20der%20Landwirtschaft-%20Ergebnisse%20eines%20mehrj%E4hrigen%20DBU-Projektes%20aus%20Baden-W%FCrttemberg.pdf|title = Startseite|date = 7 April 2003|access-date = 23 July 2021|archive-date = 22 March 2021|archive-url = https://web.archive.org/web/20210322232906/https://www.landwirtschaft-bw.info/pb/,Lde/Startseite|url-status = dead}}

In plasticulture, strawberries, tomatoes, peppers, melons, and other fruits and vegetables are grown under plastic to control temperature, retain moisture and control weeds. Compost may be banded (applied in strips along rows) and worked into the soil prior to bedding and planting, be applied at the same time the beds are constructed and plastic laid down, or used as a top dressing.

Many crops are not seeded directly in the field but are started in seed trays in a greenhouse. When the seedlings reach a certain stage of growth, they are transplanted in the field. Compost may be part of the mix used to grow the seedlings, but is not normally used as the only planting substrate. The particular crop and the seeds' sensitivity to nutrients, salts, etc. dictates the ratio of the blend, and maturity is important to insure that oxygen deprivation will not occur or that no lingering phyto-toxins remain.{{cite journal|last1=Aslam|first1=DN|last2=Vandergheynst|first2=JS|last3=Rumsey|first3=TR|year=2008|title=Development of models for predicting carbon mineralization and associated phytotoxicity in compost-amended soil|journal=Bioresour Technol|volume=99|issue=18|pages=8735–41|doi=10.1016/j.biortech.2008.04.074|pmid=18585031|bibcode=2008BiTec..99.8735A }}

Compost can be added to soil, coir, or peat, as a tilth improver, supplying humus and nutrients.{{Cite web|title=Benefits and Uses|url=http://web.extension.illinois.edu/homecompost/benefits.cfm|url-status=dead|archive-url=https://web.archive.org/web/20160219205407/http://web.extension.illinois.edu/homecompost/benefits.cfm|archive-date=19 February 2016|website=Composting for the Homeowner|publisher=University of Illinois}} It provides a rich growing medium as absorbent material. This material contains moisture and soluble minerals, which provide support and nutrients. Although it is rarely used alone, plants can flourish from mixed soil that includes a mix of compost with other additives such as sand, grit, bark chips, vermiculite, perlite, or clay granules to produce loam. Compost can be tilled directly into the soil or growing medium to boost the level of organic matter and the overall fertility of the soil. Compost that is ready to be used as an additive is dark brown or even black with an earthy smell.

Generally, direct seeding into a compost is not recommended due to the speed with which it may dry, the possible presence of phytotoxins in immature compost that may inhibit germination,{{cite journal|last1=Morel|first1=P.|last2=Guillemain|first2=G.|year=2004|title=Assessment of the possible phytotoxicity of a substrate using an easy and representative biotest|journal=Acta Horticulturae|issue=644|pages=417–423|doi=10.17660/ActaHortic.2004.644.55}}Itävaara et al. Compost maturity - problems associated with testing. in Proceedings of Composting. Innsbruck Austria 18-21.10.2000{{cite journal|vauthors=Aslam DN, etal|year=2008|title=Development of models for predicting carbon mineralization and associated phytotoxicity in compost-amended soil.|journal=Bioresour Technol|volume=99|issue=18|pages=8735–8741|doi=10.1016/j.biortech.2008.04.074|pmid=18585031|bibcode=2008BiTec..99.8735A }} and the possible tie up of nitrogen by incompletely decomposed lignin.{{cite web|title=The Effect of Lignin on Biodegradability - Cornell Composting|url=http://compost.css.cornell.edu/calc/lignin.html|url-status=live|archive-url=https://web.archive.org/web/20180927195626/http://compost.css.cornell.edu/calc/lignin.html|archive-date=27 September 2018|access-date=3 March 2009|work=cornell.edu}} It is very common to see blends of 20–30% compost used for transplanting seedlings.

Compost can be used to increase plant immunity to diseases and pests.{{Cite journal|last1=Bahramisharif|first1=Amirhossein|last2=Rose|first2=Laura E.|year=2019|title=Efficacy of biological agents and compost on growth and resistance of tomatoes to late blight|journal=Planta|volume=249|issue=3|pages=799–813|doi=10.1007/s00425-018-3035-2|issn=1432-2048|pmid=30406411|doi-access=free|bibcode=2019Plant.249..799B }}

Compost tea is made up of extracts of fermented water leached from composted materials.{{cite book|last1=Gómez-Brandón, M|title=Advances in Fertilizer Technology: Synthesis (Vol1)|last2=Vela, M|last3=Martinez Toledo, MV|last4=Insam, H|last5=Domínguez, J|date=2015|publisher=Stadium Press LLC|isbn=978-1-62699-044-9|editor1-last=Sinha, S|pages=300–318|chapter=12: Effects of Compost and Vermiculture Teas as Organic Fertilizers|editor2-last=Plant, KK|editor3-last=Bajpai, S}} Composts can be either aerated or non-aerated depending on its fermentation process.{{Cite journal |last1=St. Martin |first1=C. C.G. |last2=Brathwaite |first2=R. A.I. |date=2012 |title=Compost and compost tea: Principles and prospects as substrates and soil-borne disease management strategies in soil-less vegetable production |url=https://solvita.com/wp-content/uploads/2014/04/Compost-and-compost-tea-Principles_Martin-et-al_2012.pdf |journal=Biological Agriculture & Horticulture |volume=28 |issue=1 |pages=1–33 |doi=10.1080/01448765.2012.671516 |bibcode=2012BioAH..28....1S |issn=0144-8765 |s2cid=49226669}} Compost teas are generally produced from adding compost to water in a ratio of 1:4–1:10, occasionally stirring to release microbes.

There is debate about the benefits of aerating the mixture. Non-aerated compost tea is cheaper and less labor-intensive, but there are conflicting studies regarding the risks of phytotoxicity and human pathogen regrowth. Aerated compost tea brews faster and generates more microbes, but has potential for human pathogen regrowth, particularly when one adds additional nutrients to the mixture.

Field studies have shown the benefits of adding compost teas to crops due to organic matter input, increased nutrient availability, and increased microbial activity. They have also been shown to have a suppressive effect on plant pathogens{{cite book|last1=Santos, M|title=Natural products in plant pest management|last2=Dianez, F|last3=Carretero, F|publisher=CABI|year=2011|isbn=9781845936716|editor-last=Dubey, NK|location=Oxfordshire, UK Cambridge, MA|pages=242–262|chapter=12: Suppressive Effects of Compost Tea on Phytopathogens}} and soil-borne diseases. The efficacy is influenced by a number of factors, such as the preparation process, the type of source the conditions of the brewing process, and the environment of the crops. Adding nutrients to compost tea can be beneficial for disease suppression, although it can trigger the regrowth of human pathogens like E. coli and Salmonella.

Compost extracts are unfermented or non-brewed extracts of leached compost contents dissolved in any solvent.

Compost is sold as bagged potting mixes in garden centers and other outlets.{{cite web|title=John Innes potting compost|url=https://www.rhs.org.uk/advice/profile?pid=952|url-status=live|archive-url=https://web.archive.org/web/20200814113532/https://www.rhs.org.uk/advice/profile?pid=952|archive-date=14 August 2020|access-date=7 August 2020|publisher=Royal Horticultural Society}} This may include composted materials such as manure and peat but is also likely to contain loam, fertilizers, sand, grit, etc. Varieties include multi-purpose composts designed for most aspects of planting, John Innes formulations, grow bags, designed to have crops such as tomatoes directly planted into them. There are also a range of specialist composts available, e.g. for vegetables, orchids, houseplants, hanging baskets, roses, ericaceous plants, seedlings, potting on, etc.{{Cite web |title=Compost for Specialist Plants - Garden Advice - Westland Garden Health |url=https://www.gardenhealth.com/advice/soil-and-compost/compost-for-specialist-plants |access-date=2024-01-15 |website=Garden Health |language=en-GB}}{{Cite web |title=How to choose the best compost for your plants |url=https://www.lovethegarden.com/uk-en/article/how-to-choose-the-best-compost-for-your-plants |access-date=2024-01-15 |website=Love The Garden |language=en-gb}}

Compost can also be used for land and stream reclamation, wetland construction, and landfill cover.{{Cite web |last=US EPA |first=OLEM |date=2015-08-12 |title=Reducing the Impact of Wasted Food by Feeding the Soil and Composting |url=https://www.epa.gov/sustainable-management-food/reducing-impact-wasted-food-feeding-soil-and-composting |access-date=2022-08-18 |website=www.epa.gov |language=en}}

The temperatures generated by compost can be used to heat greenhouses, such as by being placed around the outside edges.{{Cite journal|last=Neugebauer|first=Maciej|date=10 January 2021|title=A compost heating solution for a greenhouse in north-eastern Poland in fall|url=https://www.sciencedirect.com/science/article/abs/pii/S0959652620336581|url-status=live|archive-url=https://web.archive.org/web/20210411023538/https://www.sciencedirect.com/science/article/abs/pii/S0959652620336581|archive-date=11 April 2021|access-date=29 April 2021|journal=Journal of Cleaner Production|volume=279|page=123613|doi=10.1016/j.jclepro.2020.123613|bibcode=2021JCPro.27923613N |s2cid=224919030}}

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There are process and product guidelines in Europe that date to the early 1980s (Germany, the Netherlands, Switzerland) and only more recently in the UK and the US. In both these countries, private trade associations within the industry have established loose standards, some say as a stop-gap measure to discourage independent government agencies from establishing tougher consumer-friendly standards.{{cite web|title=US Composting Council|url=http://www.compostingcouncil.org/|url-status=dead|archive-url=https://web.archive.org/web/20190415204627/https://www.compostingcouncil.org/|archive-date=15 April 2019|access-date=2013-07-18|publisher=Compostingcouncil.org}} Compost is regulated in Canada{{cite web|date=2005|title=Canadian Council of Ministers of the Environment - Guidelines for Compost Quality|url=http://www.ccme.ca/files/Resources/waste/compost_quality/compostgdlns_1340_e.pdf|url-status=dead|archive-url=https://web.archive.org/web/20151018085550/http://www.ccme.ca/files/Resources/waste/compost_quality/compostgdlns_1340_e.pdf|archive-date=18 October 2015|access-date=2017-09-04|publisher=CCME Documents}} and Australia{{cite web|date=2011|title=Organics Recycling in Australia|url=https://www.biocycle.net/2011/01/25/organics-recycling-in-australia/|url-status=live|archive-url=https://web.archive.org/web/20180922135731/https://www.biocycle.net/2011/01/25/organics-recycling-in-australia/|archive-date=22 September 2018|access-date=2017-09-04|publisher=BioCycle}} as well.

EPA Class A and B guidelines in the United States{{Cite web |url=http://www.access.gpo.gov/nara/cfr/waisidx_02/40cfr503_02.html |title=EPA Class A standards |access-date=23 July 2021 |archive-date=4 February 2012 |archive-url=https://web.archive.org/web/20120204040726/http://www.access.gpo.gov/nara/cfr/waisidx_02/40cfr503_02.html |url-status=dead }} were developed solely to manage the processing and beneficial reuse of sludge, also now called biosolids, following the US EPA ban of ocean dumping. About 26 American states now require composts to be processed according to these federal protocols for pathogen and vector control, even though the application to non-sludge materials has not been scientifically tested. An example is that green waste composts are used at much higher rates than sludge composts were ever anticipated to be applied at.{{Cite web|url=http://www.epa.gov/epawaste/conserve/tools/cpg/products/compost.htm|title=EPA regulations for compost use}} U.K guidelines also exist regarding compost quality,{{Cite web|url=http://www.wrap.org.uk/downloads/Introduction_to_BSI_PAS_100-20052.92f2ee6e.2181.pdf|title=British Standards Institute Specifications}} as well as Canadian,{{Cite web|url=http://www.compost.org/compostqualitydoc.pdf|title=Consensus Canadian national standards|access-date=23 July 2021|archive-date=9 March 2018|archive-url=https://web.archive.org/web/20180309120941/http://www.compost.org/compostqualitydoc.pdf|url-status=dead}} Australian,[http://www.environment.gov.au/settlements/publications/waste/composting/quality.html Australian quality standards] and the various European states.{{Cite web|url=https://ec.europa.eu/environment/topics/waste-and-recycling/biodegradable-waste_en|title=Biodegradable waste|website=ec.europa.eu}}

In the United States, some compost manufacturers participate in a testing program offered by a private lobbying organization called the U.S. Composting Council. The USCC was originally established in 1991 by Procter & Gamble to promote composting of disposable diapers, following state mandates to ban diapers in landfills, which caused a national uproar. Ultimately the idea of composting diapers was abandoned, partly since it was not proven scientifically to be possible, and mostly because the concept was a marketing stunt in the first place. After this, composting emphasis shifted back to recycling organic wastes previously destined for landfills. There are no bonafide quality standards in America, but the USCC sells a seal called "Seal of Testing Assurance"{{Cite web |title=US Composting Council |url=https://www.compostingcouncil.org/ |access-date=25 October 2022 |website=US Composting Council}} (also called "STA"). For a considerable fee, the applicant may display the USCC logo on products, agreeing to volunteer to customers a current laboratory analysis that includes parameters such as nutrients, respiration rate, salt content, pH, and limited other indicators.{{Cite web|url=http://www.compostingcouncil.org/programs/sta/test_methods.php|title=US Composting Council testing parameters}}

Many countries such as Wales{{cite web|title=Gwynedd Council food recycling|url=http://www.gwynedd.gov.uk/gwy_doc.asp?doc=25454&language=1&p=1&c=1|url-status=dead|archive-url=https://web.archive.org/web/20140501141531/http://www.gwynedd.gov.uk/gwy_doc.asp?doc=25454&language=1&p=1&c=1|archive-date=1 May 2014|access-date=21 December 2017}}{{cite web|title=Anglesey households achieve 100% food waste recycling|url=http://www.edie.net/news/5/Anglesey-households-achieve-100-food-waste-recycling/19101/|url-status=live|archive-url=https://web.archive.org/web/20170905052711/https://www.edie.net/news/5/Anglesey-households-achieve-100-food-waste-recycling/19101/|archive-date=5 September 2017|access-date=13 April 2013|work=edie.net}} and some individual cities such as Seattle and San Francisco require food and yard waste to be sorted for composting (San Francisco Mandatory Recycling and Composting Ordinance).{{cite web|date=2016|title=Recycling & Composting in San Francisco - Frequently Asked Questions|url=https://sfenvironment.org/recycling-composting-faqs|url-status=live|archive-url=https://web.archive.org/web/20170905003224/https://sfenvironment.org/recycling-composting-faqs|archive-date=5 September 2017|access-date=4 September 2017|publisher=San Francisco Dept. of the Environment}}{{cite news|last=Tyler|first=Aubin|date=21 March 2010|title=The case for mandatory composting|work=The Boston Globe|url=http://www.boston.com/bostonglobe/magazine/articles/2010/03/21/the_case_for_mandatory_composting/|url-status=live|access-date=19 September 2010|archive-url=https://web.archive.org/web/20100825201135/http://www.boston.com/bostonglobe/magazine/articles/2010/03/21/the_case_for_mandatory_composting/|archive-date=25 August 2010}}

The USA is the only Western country that does not distinguish sludge-source compost from green-composts, and by default 50% of US states expect composts to comply in some manner with the federal EPA 503 rule promulgated in 1984 for sludge products.{{cite web|year=1998|title=Electronic Code of Federal Regulations. Title 40, part 503. Standards for the use or disposal of sewage sludge|url=http://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&SID=ef0e4bc903a2845519f1d9129ad7eef7&rgn=div5&view=text&node=40:31.0.1.2.42&idno=40|url-status=live|archive-url=https://web.archive.org/web/20180922173729/https://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&SID=ef0e4bc903a2845519f1d9129ad7eef7&rgn=div5&view=text&node=40:31.0.1.2.42&idno=40|archive-date=22 September 2018|access-date=30 March 2009|work=U.S. Government Printing Office}}

There are health risk concerns about PFASs ("forever chemicals") levels in compost derived from sewage sledge sourced biosolids, and EPA has not set health risk standards for this. The Sierra Club recommends that home gardeners avoid the use of sewage sludge-base fertilizer and compost, in part due to potentially high levels of PFASs.{{cite web |url=https://www.sierraclub.org/sludge-garden-toxic-pfas-home-fertilizers-made-sewage-sludge#biosolids |title=Sludge in the Garden: Toxic PFAS in Home Fertilizers Made From Sewage Sludge |website=sierraclub |date=21 May 2021 |publisher=Sierra Club |access-date=29 March 2022 }} The EPA PFAS Strategic Roadmap initiative, running from 2021 to 2024, will consider the full lifecycle of PFAS including health risks of PFAS in wastewater sludge.{{cite web |title=PFAS Strategic Roadmap: EPA's Commitments to Action 2021-2024 |date=14 October 2021 |url=https://www.epa.gov/pfas/pfas-strategic-roadmap-epas-commitments-action-2021-2024 |access-date=2022-03-24 |publisher=EPA}}

File:Compost Basket.jpg

Composting dates back to at least the early Roman Empire and was mentioned as early as Cato the Elder's 160 BCE piece {{lang|la|De Agri Cultura}}.{{Cite book|chapter-url=https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Cato/De_Agricultura/A*.html|title=De Agri Cultura|last=Cato|first=Marcus|date=|chapter=37.2; 39.1|access-date=19 February 2021}}{{dead link|date=August 2023|bot=medic}}{{cbignore|bot=medic}} Traditionally, composting involved piling organic materials until the next planting season, at which time the materials would have decayed enough to be ready for use in the soil. Methodologies for organic composting were part of traditional agricultural systems around the world.

Composting began to modernize somewhat in the 1920s in Europe as a tool for organic farming.{{cite web|title=History of Composting|url=https://web.extension.illinois.edu/homecompost/history.cfm|url-status=dead|archive-url=https://web.archive.org/web/20181004232552/https://web.extension.illinois.edu/homecompost/history.cfm|archive-date=4 October 2018|access-date=11 July 2016|website=Composting for the Homeowner|publisher=University of Illinois}} The first industrial station for the transformation of urban organic materials into compost was set up in Wels, Austria, in the year 1921.Welser Anzeiger vom 05. Januar 1921, 67. Jahrgang, Nr. 2, S. 4 Early proponents of composting in farming include Rudolf Steiner, founder of a farming method called biodynamics, and Annie Francé-Harrar, who was appointed on behalf of the government in Mexico and supported the country in 1950–1958 to set up a large humus organization in the fight against erosion and soil degradation.{{Cite book|url=https://books.google.com/books?id=gETbAwAAQBAJ&q=Annie+Franc%C3%A9-Harrar+compost&pg=PA86|title=A History of the Garden in Fifty Tools|last=Laws|first=Bill|year=2014|publisher=University of Chicago Press|isbn=978-0226139937|pages=86|language=en|access-date=16 October 2020|archive-date=13 July 2021|archive-url=https://web.archive.org/web/20210713211322/https://books.google.com/books?id=gETbAwAAQBAJ&q=Annie+Franc%C3%A9-Harrar+compost&pg=PA86|url-status=live}} Sir Albert Howard, who worked extensively in India on sustainable practices, and Lady Eve Balfour were also major proponents of composting. Modern scientific composting was imported to America by the likes of J. I. Rodale – founder of Rodale, Inc. Organic Gardening, and others involved in the organic farming movement.

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• Carbon farming
• Human composting
• Organic farming
• Permaculture
• Semicomposting
• Soil science
• Sustainable agriculture
• Terra preta
• Vermicompost
• Waste sorting
• Zero waste

• List of composting systems
• List of environment topics
• List of sustainable agriculture topics
• List of organic gardening and farming topics

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