What are composting, compost, and vermicomposting?
Composting—the process of managing organic residuals, and the product—compost have been understood by mankind for at least two millennia, and likely longer, with recorded instances of their benefit to soil fertility extending back to the Roman statesman Cato. Compost is a beneficial substance aiding soil and is produced by the activity of microorganisms upon organic matter. Since organic matter (food waste, paper waste, agriculture and landscape waste, animal manures, and wastewater residuals) in many societies is abundant and often problematical, composting discarded organic waste matter is a process useful to waste managers who are concerned with, 1. reducing volume of waste and, 2. stabilizing waste that is volatile, inasmuch as it becomes a nuisance for its odor and attraction to vectors. Thus, composting is attractive to waste managers as a process technology, while the resulting product, compost, is attractive for its horticultural and agricultural benefits.
Vermicomposting (Latin vermes = worm) is a kindred process to composting, featuring the addition of certain species of earthworms used to enhance the process of waste conversion and produce a better end-product. Vermicomposting differs from composting in several ways. Chiefly, vermicomposting is a mesophilic process, utilizing microorganisms and earthworms that are active in a temperature range of 50-90 degrees Fahrenheit. [Not ambient temperature but temperature within the pile of moist organic material.] The process is considered faster than composting and, because material passes through the earthworm gut, a significant but not-yet-fully-understood transformation takes place, whereby the resulting earthworm castings (worm manure) are abundant in microbial activity and plant growth regulators, and fortified with pest repellency attributes as well! In short, earthworms, through a type of biological alchemy, are capable of transforming garbage into gold. Because of this, no less a person than Charles Darwin, a lifelong student of earthworms, wrote at the close of his treatise on earthworm castings, “It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures.” (The Formation of Vegetable Mould Through The Action of Worms With Observations on their Habits, 1881).
Vermicomposting Progress in the US—Research Level
While vermiculture (earthworm breeding) operations have been in existence throughout the United States during the 20th century, principally for the production of fishbait, interest in vermicomposting may be tied most significantly to the work of Dr. Clive Edwards at The Ohio State University since the early 1980s. Dr. Edwards brought his expertise in earthworm research gained from a project at the Rothamsted Experimental Station in the UK concerning production methods of earthworms and castings, as well as research on various types of wastes that earthworms might process. He and his colleagues developed the Continuous Flow Reactor, a mechanized process employing an elevated bed allowing addition of feedstock at the top level to a 1-2 meter-thick bed of earthworms that process material into castings which are then harvested from below the bed, allowing the earthworms to work undisturbed. This in-vessel technology is considered more efficient than the customary windrow technology in which rows of organic matter (6 feet wide, 3 feet high, dozens to hundreds of feet in length) are seeded with earthworms and are found in an outdoor environment (subject to weather, predation, and moisture variation).
In addition to the process technology Dr. Edwards has helped to spread, Ohio State University researchers have principally concentrated upon assessing the effects of vermicompost (vs. compost and commercially available growth media) on plant growth in horticultural container media and soil. Conclusive evidence points to an optimal use of 10-20% earthworm castings in a blend of container media that produces measurable improvement in root and shoot development, increase in leaf size, formation of flowers, increase in crop yield, and overall health of plants (in warding off disease). Details of these findings, however, are buried in scholarly scientific research journals, seldom finding their way to the general public. More recent efforts in castings research, both at OSU and in California, have been aimed at discovering a wide array of insect-repellency properties of castings, suggesting their use as an organic, non-toxic bio-pest repellent.
Further, research in vermicomposting’s use in treating wastewater residuals (biosolids) has been another fruitful field of inquiry. Pilot projects using earthworms in biosolids have shown nearly complete and satisfactory eradication of four indicator species of human pathogens (E. coli, Salmonella, enteric viruses, helminth ova). While not yet approved by USEPA or USDA as a viable means to render biosolids as safe for handling (to achieve the standard of Class A biosolids, having met PFRP standards), preliminary studies have shown vermicomposting may be considered a Process to Further Reduce Pathogens (PFRP), although the adoption of standard operating procedures (SOPs) and regulatory approval awaits further demonstration and testing.
Vermicomposting Progress in the US—Field Work, Marketing, Public Acceptance
Vermicomposting relies upon the regular addition of small amounts (1-inch depth) of organic feedstock at the surface of a worm bed. Greater amounts of material applied to the surface may cause the bed to heat up, a likelihood that occurs as thermophilic (heat-loving) organisms proliferate. Should temperatures increase beyond 100 degrees F in the pile, earthworms perish. One net effect of this key process requirement is that vermicomposting on a large scale tends to require a greater horizontal surface area than thermophilic composting operations. (Composting operations, in contrast to vermicomposting operations, encourage the use of thermophilic microorganisms to turn organic residuals to compost. These operations build piles of organic matter ranging in height from 8 feet and up, better utilizing surface area than vermicomposting.) The largest vermicomposting facilities in the US tend to be found in the more temperate regions, where outdoor windrows may take up to several acres of land. An example of what may be the largest vermicomposting operation in North America is Pacific Landscape Supply (formerly American Resource Recovery) in Vernalis, CA, just south of the larger city of Stockton. Over 300 wet tons of cardboard sludge (unusable, short fiber waste from a cardboard recycling facility) are delivered daily to this 360-acre operation where 70 acres of vermicomposting beds have been arranged. Earthworms process this paper waste product, transforming the material into castings that are sold in bulk to nurseries, farms, and retail bagging distributors. Earthworms are also harvested and sold separately.
Most vermicomposting facilities in the US tend to utilize manures from herbivorous animals, especially dairy manure (separated solids). Ideally, vermicomposting ventures could minimize transportation and handling costs by being situated near waste generators such as dairies, racetracks, sources of pre-consumer food waste (packing plants), wastewater treatment plants, etc. Presently, confined animal feeding operations (CAFOs) such as poultry farms and hog farms generate enormous amounts of waste and are the cause of groundwater contamination and other problems throughout several regions of the US. Vermicomposting as a waste management option has not been widely explored, however, due to a complex series of factors that are beyond the scope of this summary.
Some isolated attempts to market earthworm castings have been made during the past decade. Dr. Scott Subler, a soil ecologist who worked for eight years with Dr. Edwards at OSU, left academia to start his Living Soil company, nationally distributing and retailing small packages of earthworm castings, bottles of castings tea, and castings tea bags. There have also been other, more regionally confined efforts to market castings through nurseries and garden supply centers. As yet, the vast majority of American gardeners and consumers are not aware of earthworm castings or their benefits. Most individuals in the soil amendment and fertilizer industry would have little knowledge of these products. Castings are vastly different from petro-chemical fertilizers which have detrimental effects on microbial life in the soil. The appeal of castings would be tend to be welcomed initially by those who support organic farming inputs and sustainable agriculture practices.
International Appeal of Vermicomposting
Vermiculture has been embraced throughout the world, especially in regions where temperate weather conditions allow for implementation of outdoor systems. In India vermiculture has been employed for waste management and for the production of marketable castings. In China, where earthworms have been a traditional medicine for at least 2,300 years, vermiculture has been practiced in order to utilize earthworms as pharmaceutical agents. Clinical application includes treatment for nervous, blood, cardiovascular, and respiratory systems. Earthworm treatments have been used on, but not limited to, asthma, epilepsy, high blood pressure, schizophrenia, mumps, eczema, burns, ulcers, and cancer. In Cuba, vermicomposting animal manures began in earnest after the break-up of the USSR and the resultant loss of chemical fertilizers from the Soviet Union. In Australia, researchers Buckerfield and Webster reported at an international symposium that on established vineyards, worm-worked wastes derived from winery-waste was spread on the surface and covered with mulch. When harvested five months later, grape yields from the vermicompost treatment had increased by 35%. Yield increases in excess of 25% were achieved with cherry trees in the first year with clear evidence of larger fruit. These higher yields have been maintained for the two following annual harvests, without further additions of vermicompost. In Mexico more than 40 companies or individual farmers operate vermicomposting plants in 13 states. Production capacities range from 0.3 to 4 tons/day of castings, much of it from coffee pulp. C. Gonzales and J. Morales report that “Onan Diaz was among several peasants who learned about earthworm composting from a social support program. After obtaining worms and producing compost, he applied the finished product on his small coffee plantation. Improvement was evident as increased blooms per plant and better coffee flavor differentiated his plantation from his neighbors. The ejidataros (land owners in the region) began to worm composting too.” The authors believe “worm compost could be part of the solution for ‘damaged’ agriculture in poor regions of Mexico. Its use could slowly regenerate contaminated and impoverished soils and at the same time provide some income to rural communities. Worm farming in developing countries should be seen as a social support and an ecological defense tool,” they suggested. (“Vermicomposting Fits Needs of a Developing Country,” BioCycle: Journal of Composting & Organics Recycling, Aug. 2002, 64-69.) In early September, 2001 Peter Bogdanov of VermiCo was invited to provide technical assistance in vermiculture to Uzbekistan through a program sponsored by the International Development Division of Land O’ Lakes working with USAID. Unfortunately, the September 11th tragedy in New York City delayed this venture. At the time, the Karshi Farmer’s Extension Service showed interest in receiving experts who would introduce local farmers to the benefits of vermicomposting. Details on this offer (“Opportunity for Vermiculture Consulting in Uzbekistan”) are found in the VermiCo subscription newsletter Casting Call, Vol. 6, Issue 3, October 2001, 6-7.
Vermicomposting technology is known throughout the world, albeit in limited areas. It may be considered a widely spread, though not necessarily popular technology. As a process for handling organic residuals, it represents an alternative approach in waste management, inasmuch as the material is neither landfilled nor burned but is considered a resource that may be recycled. In this sense, vermicomposting is compatible with sound environmental principles that value conservation of resources and sustainable practices. Vermicomposting is akin to composting in that similar feedstocks—organic residuals—are used. Both systems utilize microbial activity to break down organic matter in a moist, aerobic environment Vermicomposting differs from thermophilic composting in several ways: Vermicomposting is faster, produces fewer odors and produces a superior product. However vermicomposting requires greater surface area, more moisture, and is susceptible to heat, high salt levels, high ammonia levels, anaerobic conditions, and substances that may be toxic to earthworms (such as avermectins used to treat intestinal worms in cattle.) Of the 4,400 identified earthworm species, specific species of litter-dwelling earthworms are required for this process (classified as epigeic earthworms, they tend to be more pigmented than the other species that create burrows and live in soil). Limiting factors for vermicomposting include insufficient water supply, extremely cold weather conditions, poor quality of feedstocks, high salinity in feedstocks, poor management of worm beds, limited surface area, and lack of suitable species and ready supply of earthworms to begin and continue the task. Although composting earthworms may multiply rapidly when the key process variables are present and at optimum levels, it takes time for a small number of earthworms to multiply. Some have claimed that earthworms may double their biomass every 90 days or thereabouts. Sufficient scientific study has neither confirmed nor denied the oft-claimed exponential rates of which earthworms are said to proliferate. However, abundant anecdotal evidence confirms that earthworms are capable of multiplying rapidly, where conditions are optimal.
Vermicomposting in developing countries could prove to be useful in many instances. Some aspects of the process may be labor intensive when mechanized equipment such as front-end loaders, trommel screens, tractors, etc., are not available to handle large volumes of material. In areas where creation of low or semi-skilled jobs is considered advantageous, vermicomposting may supply an opportunity for employment. Where accumulation of food waste, paper, cardboard, agriculture waste, manures, and biosolids is problematical, composting and vermicomposting offer potential to turn waste material into a valuable soil amendment.
In areas where poor soils are prevalent, increase of organic matter becomes necessary. Compost alone is suggested for both clay and sandy soils. Compost helps break up clay soils, providing increased friability. In sandy soils, compost improves moisture retention. Mostly, compost aids in providing humus and increasing the diversity of the soil food web consisting of millions of microorganisms, critical for healthy plant growth. Vermicompost, a more valuable commodity, is best used sparingly such as in container media, greenhouse application, establishing new plants such as rootstock in vineyards, and wherever it can be directed in close proximity to plants. Increasingly, aerobically-produced compost teas and castings teas are proving to have value when used as foliar sprays and soil drenches.
A two-part program, consisting of both composting and vermicomposting, may be useful when introducing the concept of adding organic material for agricultural and horticultural production. Composting is, by far, the simpler of the two processes and involves fewer risks. Where soil is severely lacking organic matter, the addition of compost alone would pay huge dividends. Once composting has been implemented in a new situation, vermicomposting may be introduced later on as a secondary process, offering a better product but requiring better management as well.