and nutrients. although it is rarely used alone, plants can flourish from mixed soil, 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, 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 a kitchen compost bin is used to transport compostable items to an outdoor compost bin. 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 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. 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 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). 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 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 compost basket composting dates back to at least the early roman empire, and was mentioned as early as cato the elder's 160 bce piece de agri cultura. 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 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, who worked extensively in india 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 and helen nearing – inspired the back-to-the-land movement of the 1960s