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Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting mixture is rich in plant nutrients and beneficial organisms, such as bacteria, protozoa, nematodes and fungi. Compost improves soil fertility in
garden A garden is a planned space, usually outdoors, set aside for the cultivation, display, and enjoyment of plants and other forms of nature. The single feature identifying even the wildest wild garden is ''control''. The garden can incorporate bot ...
s,
landscaping Landscaping refers to any activity that modifies the visible features of an area of land, including the following: # Living elements, such as flora or fauna; or what is commonly called gardening, the art and craft of growing plants with a goal ...
,
horticulture Horticulture is the branch of agriculture that deals with the art, science, technology, and business of plant cultivation. It includes the cultivation of fruits, vegetables, nuts, seeds, herbs, sprouts, mushrooms, algae, flowers, seaweeds and no ...
,
urban agriculture Urban agriculture, urban farming, or urban gardening is the practice of cultivating, processing, and distributing food in or around urban areas. It encompasses a complex and diverse mix of food production activities, including fisheries and ...
, and organic farming, reducing dependency on commercial chemical fertilizers. The benefits of compost include providing nutrients to crops as
fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
, acting as a soil conditioner, increasing the humus or humic acid contents of the soil, and introducing beneficial microbes that help to suppress pathogens in the soil and reduce soil-borne diseases. At the simplest level, composting requires gathering a mix of 'greens' (green waste) and 'browns' (brown waste). Greens are materials rich in nitrogen such as leaves, grass, and food scraps. Browns are woody materials rich in carbon, such as stalks, paper, and wood chips. The materials break down into humus in a process taking months. Composting can be a multi-step, closely monitored process with measured inputs of water, air, and carbon- and nitrogen-rich materials. The
decomposition Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and ...
process is aided by shredding the plant matter, adding water, and ensuring proper aeration by regularly turning the mixture in a process using open piles or "
windrow A windrow is a row of cut (mown) hay or small grain crop. It is allowed to dry before being baled, combined, or rolled. For hay, the windrow is often formed by a hay rake, which rakes hay that has been cut by a mowing machine or by scythe into ...
s."
Fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...
,
earthworm An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. T ...
s, and other detritivores further break up the organic material. Aerobic bacteria and fungi manage the chemical process by converting the inputs into heat,
carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...
, and ammonium. Composting is an important part of waste management, since food and other compostable materials make up about 20% of waste in landfills, and these materials take longer to biodegrade in the landfill. Composting offers an environmentally superior alternative to using organic material for landfill because composting reduces anaerobic methane emissions, and provides economic and environmental co-benefits. For example, compost can also be used for land and stream reclamation, wetland construction, and landfill cover.


Fundamentals

Composting is an aerobic method of decomposing organic solid wastes. It can therefore 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 A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
for plants. Composting organisms require four equally important ingredients to work effectively: *Carbon is needed for energy; the microbial
oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or ...
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 anaerobic conditions. Certain ratios of these materials will 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 with a pitchfork) is needed to maintain sufficient oxygen and the right moisture level. The air/water balance is critical to maintaining high temperatures until the materials are broken down. Composting is most efficient with a
carbon-to-nitrogen ratio A carbon-to-nitrogen ratio (C/N ratio or C:N ratio) is a ratio of the mass of carbon to the mass of nitrogen in organic residues. It can, amongst other things, be used in analysing sediments and soil including soil organic matter and soil amendme ...
of about 25:1. 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 ~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. Nearly all dead plant and animal materials have both carbon and nitrogen in different amounts. 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

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.


Chemical decomposers

*
Bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
– the most abundant and important of all the
microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in old ...
s 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 A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, with an optimum growth range from . The optimum growth temperature for these organisms is 37°C. The term is mainly applied to microorganisms. Org ...
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 bio-available for plants. ** Thermophilic bacteria do not reproduce and are not active between , yet are found throughout soil. They activate once the mesophilic bacteria have begun to breakdown 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. Thermophilic bacteria thrive at higher temperatures, reaching in typical mixes. Large-scale composting operations, such as windrow composting, may exceed this temperature, potentially killing beneficial soil microorganisms but also
pasteurizing Pasteurization or pasteurisation is a process of food preservation in which packaged and non-packaged foods (such as milk and fruit juices) are treated with mild heat, usually to less than , to eliminate pathogens and extend shelf life. Th ...
the waste. ** Actinomycetota are needed to break down paper products such as newspaper,
bark Bark may refer to: * Bark (botany), an outer layer of a woody plant such as a tree or stick * Bark (sound), a vocalization of some animals (which is commonly the dog) Places * Bark, Germany * Bark, Warmian-Masurian Voivodeship, Poland Arts, e ...
, 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 A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...
such as mold and
yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constit ...
help break down materials that bacteria cannot, especially cellulose and lignin in woody material. * Protozoa – contribute to biodegradation of organic matter as well as consuming non-active bacteria, fungi, and micro-organic particulates.


Physical decomposers

*Ants – create nests, making the soil more porous and transporting nutrients to different areas of the compost. *Beetles – grubs feed on decaying vegetables. *
Earthworm An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. T ...
s – 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 input 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, mold, and decomposing plants.


Phases of composting

Under ideal conditions, composting proceeds through three major phases: #Mesophilic phase: an initial, mesophilic phase, in which the decomposition is carried out under moderate temperatures by mesophilic microorganisms. #Thermophilic phase: as the temperature rises, a second, thermophilic phase starts, in which various thermophilic bacteria carry out the decomposition under higher temperatures (.) #Maturation phase: as the supply of high-energy compounds dwindles, the temperature starts to decrease, and the mesophilic bacteria once again predominate in the maturation phase.


Hot and cold composting – impact on timing

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 will 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 eighteen days. It requires assembly of at least of material at the outset and needs turning every two days after an initial four-day phase. 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. 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 tend not to reach and maintain high temperatures. Turning is not necessary with cold composting, although there is a risk that parts of the pile may go anaerobic as they become compacted or water-logged.


Pathogen removal

Composting can destroy some
pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a g ...
s and
seed A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosper ...
s, by reaching temperatures above . Dealing with stabilized compost – i.e. composted material in which microorganisms have finished digesting the organic matter and the temperature has reached between – poses very little risk, as these temperatures kill pathogens and even make
oocysts Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism is ...
unviable. The temperature at which a pathogen dies depends on the pathogen, how long the temperature is maintained (seconds to weeks), and pH. Compost products like compost tea and compost extracts have been found to have an inhibitory effect on '' Fusarium oxysporum'', ''Rhizoctonia'' sp., and ''
Pythium debaryanum ''Pythium debaryanum'' is a species of water mould in the family Pythiaceae. It is known as a plant pathogen on many kinds of wild and cultivated plants, including peanut, beet, eucalyptus, tobacco, and pine trees. The plants develop damping off ...
,'' plant pathogens that can cause crop diseases. 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. 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.


Diseases that can be contracted from handling compost

When turning compost that has not gone through phases where temperatures above are reached, a mouth mask and gloves must be worn to protect from diseases that can be contracted from handling compost, including: *
Aspergillosis Aspergillosis is a fungal infection of usually the lungs, caused by the genus ''Aspergillus'', a common mould that is breathed in frequently from the air around, but does not usually affect most people. It generally occurs in people with lung dis ...
*
Farmer's lung Farmer's lung (not to be confused with silo-filler's disease) is a hypersensitivity pneumonitis induced by the inhalation of biologic dusts coming from hay dust or mold spores or any other agricultural products. It results in a type III hypersen ...
* Histoplasmosis – a fungus that grows in guano and bird droppings * Legionnaires' disease * Paronychia – via infection around the fingernails and toenails *
Tetanus Tetanus, also known as lockjaw, is a bacterial infection caused by ''Clostridium tetani'', and is characterized by muscle spasms. In the most common type, the spasms begin in the jaw and then progress to the rest of the body. Each spasm usually ...
– a central nervous system disease
Oocyte An oocyte (, ), oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female ...
s are rendered unviable by temperatures over . Environmental Benefits 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 less trips which in turn lowers the overall emissions from the waste management fleet.


Materials that can be composted

Potential sources of compostable materials, or feedstocks, include residential, agricultural, and commercial waste streams. Residential food or yard waste can be composted at home, 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.


Organic solid waste

There are two broad categories of organic solid waste: green waste and brown waste. 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. 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. Products derived from wood such as paper and plain cardboard are also considered carbon sources.


Animal manure and bedding

On many farms, the basic composting ingredients are animal manure generated on the farm as a
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
source, and bedding as the carbon source. Straw and sawdust are common bedding materials. Non-traditional 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.


Human excreta

Human excreta, sometimes called "humanure" in the composting context, can be added as an input to the composting process since it is a nitrogen-rich organic material. It can be either composted directly in
composting toilets A composting toilet is a type of dry toilet that treats human waste by a biological process called composting. This process leads to the decomposition of organic matter and turns human waste into compost-like material. Composting is carried ou ...
, or indirectly in the form of
sewage sludge Sewage sludge is the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater. The term " septage" also refers to sludge from simple wastewater treatment but is connected to s ...
after it has undergone treatment in a
sewage treatment plant Sewage treatment (or domestic wastewater treatment, municipal wastewater treatment) is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable for discharge to the surrounding en ...
. Both processes require capable design as there are potential health risks that 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. 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 Biosolids are solid organic matter recovered from a sewage treatment process and used as fertilizer. In the past, it was common for farmers to use animal manure to improve their soil fertility. In the 1920s, the farming community began also to use ...
, can be contaminated with a variety of metals and pharmaceutical compounds. Insufficient processing of biosolids can also lead to problems when the material is applied to land.
Urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellul ...
can be put on compost piles or directly used as fertilizer. Adding urine to compost can increase temperatures and therefore increase its ability to destroy pathogens and unwanted seeds. Unlike feces, urine does not attract disease-spreading flies (such as houseflies or
blowflies The Calliphoridae (commonly known as blow flies, blow-flies, carrion flies, bluebottles, greenbottles, or cluster flies) are a family of insects in the order Diptera, with almost 1,900 known species. The maggot larvae, often used as fishing ...
), and it does not contain the most hardy of pathogens, such as parasitic worm eggs.


Animal remains

Animal carcasses may be composted as a disposal option. Such material is rich in nitrogen.


Human body

Composting, or formally "natural organic reduction", is an emerging approach to the environmentally-friendly
disposal of human corpses Disposal of human corpses, also called final disposition, is the practice and process of dealing with the remains of a deceased human being. Disposal methods may need to account for the fact that soft tissue will decompose relatively rapidly, w ...
. Mixed with wood chips and aerated, a human corpse turns into compost in a month. The idea is growing in popularity, particularly in the United States where a number of states have either legalized the process or are in the process of doing so. On September 9th, 2022, California governor Gavin Newsom signed a bill that would allow human composting in California. Burial, cremation and alkaline hydrolysis were the only choices of death care, but with the new bill signed into action, human composting, or natural organic reduction, will be an additional option for “individuals who want a different method to honor their remains after death.” The bill is set to take effect in 2027.


Composting technologies


Industrial-scale


In-vessel composting


Aerated static pile composting


Windrow composting


Other systems at household level


Hügelkultur (raised garden beds or mounds)

The practice of making raised garden beds or mounds filled with rotting wood is also called in German. It is in effect creating a nurse log that is covered with soil. Benefits of garden beds include water retention and warming of soil. Buried wood acts like a
sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate throu ...
as it decomposes, able to capture water and store it for later use by crops planted on top of the bed.


Composting toilets


Related technologies

*
Vermicompost Vermicompost (vermi-compost) is the product of the decomposition process using various species of worms, usually red wigglers, white worms, and other earthworms, to create a mixture of decomposing vegetable or food waste, bedding materials, and ...
(also called worm castings, worm humus, worm manure, or worm faeces) is the end-product of the breakdown of organic matter by earthworms. These castings have been shown to contain reduced levels of contaminants and a higher saturation of nutrients than the organic materials before vermicomposting. * 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 * 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 non-compostable 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 Sewage sludge is the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater. The term " septage" also refers to sludge from simple wastewater treatment but is connected to s ...
. *
Anaerobic digestion Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to manage waste or to produce fuels. Much of the ferm ...
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 In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
from fugitive
methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane ...
; untreated waste breaks down anaerobically in a landfill, producing
landfill gas Landfill gas is a mix of different gases created by the action of microorganisms within a landfill as they decompose organic waste, including for example, food waste and paper waste. Landfill gas is approximately forty to sixty percent methane ...
that contains methane, a potent greenhouse gas. The methane produced in an anaerobic digester can be converted to biogas.


Uses


Agriculture and gardening

On open ground for growing
wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...
, corn,
soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses. Traditional unfermented food uses of soybeans include soy milk, from which tofu ...
s, 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 ) and worked into the soil prior to planting. Application rates of 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". In plasticulture,
strawberries The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown hybrid species of the genus '' Fragaria'', collectively known as the strawberries, which are cultivated worldwide for their fruit. The fruit is widely ap ...
,
tomato The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish word ...
es, peppers,
melon A melon is any of various plants of the family Cucurbitaceae with sweet, edible, and fleshy fruit. The word "melon" can refer to either the plant or specifically to the fruit. Botanically, a melon is a kind of berry, specifically a "pepo". T ...
s, 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 '' A.N.T. Farm'' is a Disney Channel original series that follows Chyna Parks (China Anne McClain) and her two best friends, Olive Doyle ( Sierra McCormick) and Fletcher Quimby (Jake Short), who are in the "Advanced Natural Talents" (A.N.T.) progr ...
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. Compost can be added to soil, coir, or
peat Peat (), also known as turf (), is an accumulation of partially Decomposition, decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, Moorland, moors, or muskegs. The peatland ecosystem covers and ...
, as a tilth improver, supplying humus and nutrients. 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 Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ...
,
sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class ...
, grit, bark chips, vermiculite, perlite, or
clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay pa ...
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, and the possible tie up of nitrogen by incompletely decomposed lignin. 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.


Compost tea

Compost tea is made up of extracts of fermented water leached from composted materials. Composts can be either aerated or non-aerated depending on its fermentation process. 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. 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 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 extract

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


Commercial sale

Compost is sold as bagged potting mixes in garden centers and other outlets. 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.


Other

Compost can also be used for land and stream reclamation, wetland construction, and landfill cover. The temperatures generated by compost can be used to heat greenhouses, such as by being placed around the outside edges.


Regulations

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. Compost is regulated in Canada and Australia as well. EPA Class A and B guidelines in the United States were developed solely to manage the processing and
beneficial reuse Waste valorization, beneficial reuse, value recovery or waste reclamation is the process of waste products or residues from an economic process being valorized (given economic value), by reuse or recycling in order to create economically useful ...
of sludge, also now called
biosolids Biosolids are solid organic matter recovered from a sewage treatment process and used as fertilizer. In the past, it was common for farmers to use animal manure to improve their soil fertility. In the 1920s, the farming community began also to use ...
, 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 In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a g ...
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. U.K guidelines also exist regarding compost quality, as well as Canadian, Australian, and the various European states. 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" (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. Many countries such as
Wales Wales ( cy, Cymru ) is a country that is part of the United Kingdom. It is bordered by England to the east, the Irish Sea to the north and west, the Celtic Sea to the south west and the Bristol Channel to the south. It had a population in ...
and some individual cities such as Seattle and
San Francisco San Francisco (; Spanish for " Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the fourth most populous in California and 17t ...
require food and yard waste to be sorted for composting (
San Francisco Mandatory Recycling and Composting Ordinance The San Francisco Mandatory Recycling and Composting Ordinance (No. 100-09) is a local municipal ordinance requiring all persons located in San Francisco to separate their recyclables, compostables and landfilled trash and to participate in recyclin ...
). 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. There are health risk concerns about PFASs ("forever chemicals") levels in compost derived from sewage sledge sourced biosolids, and
EPA The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...
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. 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.


History

Composting dates back to at least the early Roman Empire, and was mentioned as early as
Cato the Elder Marcus Porcius Cato (; 234–149 BC), also known as Cato the Censor ( la, Censorius), the Elder and the Wise, was a Roman soldier, senator, and historian known for his conservatism and opposition to Hellenization. He was the first to write hi ...
's 160 BCE piece . 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. The advantage of this method is that little working time or effort is required from the composter and it fits in naturally with agricultural practices in temperate climates. Disadvantages (from the modern perspective) are that space is used for a whole year, some nutrients might be leached due to exposure to rainfall, and disease-producing organisms and insects may not be adequately controlled. Composting began to modernize somewhat from the 1920s in Europe as a tool for organic farming. The first industrial station for the transformation of urban organic materials into compost was set up in Wels, Austria in the year 1921. Early proponents of composting within 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 Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...
and supported the country in 1950–1958 to set up a large humus organization in the fight against erosion and soil degradation.
Sir Albert Howard Sir Albert Howard (8 December 187320 October 1947) was an English botanist. His academic background might have been botany. While working in India he was generally considered a Pathologist; this more than likely being the reason for his consist ...
, who worked extensively in
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
on sustainable practices, and Lady Eve Balfour were also major proponents of composting. Composting was imported to America by the likes of: * J. I. Rodale – founder of Rodale, Inc. Organic Gardening * Paul Keene – founder of Walnut Acres in Pennsylvania * and
Scott Scott may refer to: Places Canada * Scott, Quebec, municipality in the Nouvelle-Beauce regional municipality in Quebec * Scott, Saskatchewan, a town in the Rural Municipality of Tramping Lake No. 380 * Rural Municipality of Scott No. 98, Sask ...
and Helen Nearing – inspired the back-to-the-land movement of the 1960s


See also

* Carbon farming * Human composting * Organic farming *
Permaculture Permaculture is an approach to land management and settlement design that adopts arrangements observed in flourishing natural ecosystems. It includes a set of design principles derived using whole-systems thinking. It applies these principl ...
*
Soil science Soil science is the study of soil as a natural resource on the surface of the Earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils; and these properties in relation to ...
* Sustainable agriculture *
Terra preta ''Terra preta'' (, locally , literally "black soil" in Portuguese) is a type of very dark, fertile anthropogenic soil (anthrosol) found in the Amazon Basin. It is also known as "Amazonian dark earth" or "Indian black earth". In Portuguese its ful ...
* Waste sorting *
Zero waste Zero waste is a set of principles focused on waste prevention that encourages redesigning resource life cycles so that all products are reused. The goal of this movement is to avoid sending trash to landfills, incinerators, or the ocean. Cur ...


Related lists

*
List of composting systems This is a list of composting systems: Home composting (small-scale) * Bokashi (horticulture) *Composting toilet * Container composting * Ecuador composting method * Hot container composting * Hügelkultur a.k.a. German mound * Sheet mulching * Tr ...
* List of environment topics *
List of sustainable agriculture topics The following outline is provided as an overview of and topical guide to sustainable agriculture: Sustainable agriculture – applied science that integrates three main goals, environmental health, economic profitability, and social and eco ...
*
List of organic gardening and farming topics The following outline is provided as an overview of and topical guide to organic gardening and farming: Organic farming – alternative agricultural system that relies on fertilizers of organic origin such as compost, manure, green manure, ...


References

{{Authority control Organic fertilizers Waste management Gardening aids Sanitation Soil improvers Soil Sustainable food system Biodegradable waste management Permaculture