Compost (pronounced /ˈkɒmpɒst/ or /ˈkɒmpoʊst/) is composed of organic materials derived from plants and animal that has been decomposed largely through aerobic decomposition. The process of composting is simple and practiced by individuals in their homes, farmers on their land, and industrially by industries and cities.

Compost is rich in nutrients. It is used in gardens, landscaping, horticulture, and agriculture. The compost itself is beneficial for the land in many ways, including as a soil conditioner, a fertilizer to add vital humus or humic acids, and as a natural pesticide for soil. In ecosystems, compost is useful for erosion control, land and stream reclamation, wetland construction, and as landfill cover (see compost uses).

History Edit

Composting as a recognized practice dates to at least the early Roman era since Pliny the Elder (AD 23-79) who refers to compost in his writings. Traditionally, composting was to pile organic materials and let them stand for about a year, or until the next planting season, at which time the materials would be ready for soil application. The main 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, some weed, weed seeds and insects may not be adequately controlled.

Composting was somewhat modernized beginning in the 1920s in Europe as a tool for organic farming.[1] The first industrial station for the transformation of urban organic materials into compost was set up in Wels/Austria in the year 1921.[2] The early personages most cited for propounding composting within farming are for the German-speaking world 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 1950-1958 to set up a large humus organization in the fight against erosion and soil degradation. In the English-speaking world it was Sir Albert Howard who worked extensively in India on sustainable practices and Lady Eve Balfour who was a huge proponent of composting. Composting was imported to America by various followers of these early European movements in the form of persons such as J.I. Rodale (founder of Rodale Organic Gardening), E.E. Pfeiffer (who developed scientific practices in biodynamic farming), Paul Keene (founder of Walnut Acres in Pennsylvania), and Scott and Helen Nearing (who inspired the back-to-land movement of the 1960s). Coincidentally, some of these personages met briefly in India - all were quite influential in the U.S. from the 1960s into the 1980s.

There are many modern proponents of rapid composting which attempt to correct some of the perceived problems associated with traditional, slow composting. Many advocate that compost can be made in 2 to 3 weeks [3]. Many such short processes involve a few changes to traditional methods, including smaller, more homogenized pieces in the compost, controlling carbon to nitrogen (CN) ratio at 30 to 1 or less, and monitoring the moisture level more carefully. However, none of these parameters differ significantly from early writings of Howard and Balfour, suggesting that in fact modern composting has not made significant advances over traditional a few months time. For this reason and others, many modern scientists who deal with carbon transformations are skeptical that there is a "super-charged" way to get nature to make compost rapidly.[citation needed] They also point to the fact that it is the structure of the natural molecules - such as carbohydrates, proteins, and cellulose - that really dictate the rate at which microbial-mediated transformations are possible.


Composting in the Escuela Barreales

Home compost barrel in the Escuela Barreales, Chile.

Composting organisms require four equally important things to work effectively:

  • Carbon — for energy; the microbial oxidation of carbon produces the heat.
    • High carbon materials tend to be brown and dry.
  • Nitrogen — to grow and reproduce more organisms to oxidize the carbon.
    • High nitrogen materials tend to be green (or colorful, like fruits and vegetables) and wet.[4]
  • Oxygen — for oxidizing the carbon, the decomposition process.
  • Water — in the right amounts to maintain activity without causing anaerobic conditions.
Compost pile

Materials in a compost pile.

Certain ratios of these elements will provide beneficial bacteria with the nutrients to work at a rate that will heat up the pile. In that process much water will be released as vapor ("steam"), and the oxygen will be quickly depleted, explaining the need to actively manage the pile. The hotter the pile gets, the more often added air and water is necessary; the air/water balance is critical to maintaining high temperatures until the materials are broken down. At the same time, too much air or water also slows the process, as does too much carbon (or too little nitrogen).

The most efficient composting occurs with a carbon:nitrogen mix of about 30 to 1. All organics have both carbon and nitrogen, but amounts vary widely, with characteristics noted above (dry/wet, brown/green).[5] Fresh grass clippings have an average ratio of about 15 to 1 and dry autumn leaves about 50 to 1 depending on species. Mixing equal parts by volume approximates the ideal C:N range. Few individual situations will provide the ideal mix of materials at any point in time - in this respect, home composting is like horseshoes, perfect is great, but close still works. Observation of amounts, and consideration of different materials[6] as a pile is built over time, can quickly achieve a workable technique for the individual situation.


The urea in urine can be toxic to plants or can create toxic substances if not captured by sorbents and allowed to compost aerobically.

Adding a healthy person's urine may increase temperatures of mulch/compost and therefore increase its ability to destroy pathogens and unwanted seeds. Fresh urine from a person with no obvious symptoms of infection, is generally much safer than fresh feces. Unlike feces, urine doesn't attract disease-spreading flies (such as house flies or blow flies), nor does it harbor the most hardy of pathogens, such as parasitic worm eggs. Urine usually doesn't stink for long, particularly when fresh and deposited on/under sorbents.


With the proper mixture of water, oxygen, carbon, and nitrogen, microorganisms are allowed to break down organic matter to produce compost[7]. Microorganisms are absolutely necessary for the composting process and without them, organic matter in your compost heap cannot undergo the composting process. There are five types of microorganisms found in active compost[8]:

  • Bacteria- The most common of all the microorganisms found in compost.
  • Actinomycetes- Necessary for breaking down paper products such as newspaper, bark, etc.
  • Fungi- Molds and yeast help break down materials that bacteria cannot.
  • Protozoa- Help consume bacteria and fungi, balancing out the composting cycle.
  • Rotifers- Rotifers also help break down organics in the compost and also ingest bacteria and fungi.

The lack of microorganisms is the main reason why organic materials have difficulty breaking down in landfills.


Compost is generally recommended as an additive to soil, or other matrices such as coir and peat, as a tilth improver, supplying humus and nutrients. It provides a rich growing medium, or a porous, absorbent material that holds moisture and soluble minerals, providing the support and nutrients in which plants can flourish, although it is rarely used alone, being primarily mixed with soil, sand, grit, bark chips, vermiculite, perlite, or clay granules to produce loam.

Generally, direct seeding into a compost is not recommended due to the speed with which it may dry and the possible presence of phytotoxins which may inhibit germination,[9][10][11] and the possible tie up of nitrogen by incompletely decomposed lignin.[12] It is very common to see blends of 20–30% compost used for transplanting seedlings at cotyledon stage or later.

Destroying pathogens, seeds, or unwanted plants Edit

Composting can destroy pathogens or unwanted seeds. Unwanted living plants (or weeds) can be destroyed by covering with mulch/compost.

The "microbial pesticides" in compost may include thermophiles and mesophiles, however certain composting detritivores such as black soldier fly larvae and redworms, also reduce many pathogens. Theromophilic (high-temperature) composting is well known to completely destroy (nearly) all seeds and pathogens (besides prions).

The sanitizing qualities of (thermophilic) composting are desirable where there is a high likelihood of pathogens, such as with manure. Applications include humanure composting or the deep litter technique.


Compost teaEdit

Compost tea is a liquid solution or suspension made by steeping compost in water. It is used as both a fertilizer and in attempts to prevent plant diseases.[13] The liquid is applied as a spray to non-edible plant parts, or as a soil-drench (root dip), such as seedlings, or as a surface spray to reduce incidence of harmful phytopathogenic fungi in the phyllosphere.[14]



Rotary screen harvested worm castings

Vermicompost is the product of composting utilizing various species of worms, usually red wigglers, white worms, and earthworms to create a heterogeneous mixture of decomposing vegetable or food waste, bedding materials, and vermicast. Vermicast, similarly known as worm castings, worm humus or worm manure, is the end-product of the breakdown of organic matter by species of earthworm.[15]

The earthworm species (or composting worms) most often used are Red Wigglers (Eisenia foetida or Eisenia andrei), though European nightcrawlers (Eisenia hortensis) could also be used. Users refer to European nightcrawlers by a variety of other names, including dendrobaenas, dendras, and Belgian nightcrawlers.

Containing water-soluble nutrients, vermicompost is a nutrient-rich organic fertilizer and soil conditioner.[16]

Bokashi compostEdit

Bokashi bin - inside

Inside a recently started Bokashi bin. The aerated base is just visible through the food scraps and Bokashi bran.

Bokashi is a method of intensive composting. It can use an aerobic or anaerobic inoculation to produce the compost. Once a starter culture is made, it can be used to extend the culture indefinitely, like yogurt culture. Since the popular introduction of effective microorganisms (EM), Bokashi is commonly made with only molasses, water, EM, and wheat bran.

In home composting applications, kitchen waste is placed into a container which can be sealed with an air tight lid. These scraps are then inoculated with a Bokashi EM mix. This usually takes the form of a carrier, such as rice hulls, wheat bran or saw dust, that has been inoculated with composting micro-organisms. The EM are natural lactic acid bacteria, yeast, and phototrophic bacteria that act as a microbe community within the kitchen scraps, fermenting and accelerating breakdown of the organic matter. The user would place alternating layers of food scraps and Bokashi mix until the container is full.

Alternative to landfillingEdit

As concern about landfill space increases, worldwide interest in recycling by means of composting is growing, since composting is a process for converting decomposable organic materials into useful stable products.[17] Industrial scale composting in the form of in-vessel composting, aerated static pile composting, and anaerobic digestion takes place in most Western countries now, and in many areas is mandated by law. There are process and product guidelines in Europe that date to the early 1980s (Germany, Holland, 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. See: UK[18] and for the US see [19]. The USA is the only Western country that does not distinguish sludge-source compost from green-composts, and by default in the USA 50% of states expect composts to comply in some manner with the federal EPA 503 rule promulgated in 1984 for sludge products.[20] Compost is regulated in Canada and Australia as well.

Industrial systems Edit

Spontaneous combustion of compost pile

A large compost pile that can spontaneously combust if not properly managed.

Industrial composting systems are increasingly being installed as a waste management alternative to landfills, along with other advanced waste processing systems. Mechanical sorting of mixed waste streams combined with anaerobic digestion or in-vessel composting, is called mechanical biological treatment, increasingly 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.

Large-scale composting systems are used by many urban centers around the world. Co-composting is a technique which combines solid waste with de-watered biosolids, although difficulties controlling inert and plastic contamination from municipal solid waste makes this approach less attractive. The world's largest MSW co-composter is the Edmonton Composting Facility in Edmonton, Alberta, Canada, which turns 220,000 tonnes of residential solid waste and 22,500 dry tonnes of biosolids per year into 80,000 tonnes of compost. The facility is 38,690 meters2 (416,500 ft2), equivalent to 4½ Canadian football fields, and the operating structure is the largest stainless steel building in North America, the size of 14 NHL rinks.[21]

See also Edit


  1. Heckman, J. 2006. A history of organic farming: transitions from Sir Albert Howard’s War in the Soil to USDA National Organic Program. Renew. Agric. Food Syst. 21:143–150.
  2. Welser Anzeiger vom 05. Januar 1921, 67. Jahrgang, Nr. 2, S. 4
  3. The Rapid Compost Method by Robert D. Raabe, Professor of Plant Pathology, Berkeley
  4. Materials for composting - University of Illinois extension, retrieval date: 3/12/2009
  5. Klickitat County WA, USA Compost Mix Calculator
  6. Effect of lignin content on bio-availability
  9. Morel, P. and Guillemain, G. 2004. Assessment of the possible phytotoxicity of a substrate using an easy and representative biotest. Acta Horticulture 644:417–423
  10. Itävaara et al. Compost maturity - problems associated with testing. in Proceedings of Composting. Innsbruck Austria 18-21.10.2000
  11. Phytotoxicity and maturation
  12. Effect of lignin content on bio-availability
  13. Zhang, W., Han, D. Y., Dick, W. A., Davis, K. R., and Hoitink, H. A. J. 1998. Compost and compost water extract-induced systemic acquired resistance in cucumber and Arabidopsis. Phytopathology 88:450-455.
  14. Tränkner, A. 1992. Use of agricultural and municipal organic wastes to develop suppressiveness to plant pathogens. in: Biological Control of Plant Diseases. E. C. Tjamos, G. C. Papavizas, and R. J. Cook, eds. Plenum Press, New York.
  15. "Paper on Invasive European Worms". Retrieved 2009-02-22. 
  16. Coyne, Kelly and Erik Knutzen. The Urban Homestead: Your Guide to Self-Sufficient Living in the Heart of the City. Port Townsend: Process Self Reliance Series, 2008.
  17. A Brief History of Solid Waste Management
  18. British Standards Institute Specifications FAQ
  19. [1]
  20. U.S. Government Printing Office. 1998. Electronic Code of Federal Regulations. Title 40, part 503. Standards for the use or disposal of sewage sludge. Available at: ecfr&tpl /ecfrbrowse/Title40/40cfr503 main 02.tpl. Accessed 30 March 2009.
  21. Edmonton composting facility


  • Insam, H; Riddech, N; Klammer, S (Eds.): Microbiology of Composting ,Springer Verlag, Berlin New York 2002, ISBN 978-3-540-67568-6
  • Hogg, D., J. Barth, E. Favoino, M. Centemero, V. Caimi, F. Amlinger, W. Devliegher, W. Brinton., S. Antler. 2002. Comparison of compost standards within the EU, North America, and Australasia. Waste and Resources Action Programme Committee (UK) (see

External linksEdit

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