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Worms for Composting (Vermicomposting) |
| By Alice Beetz NCAT Agriculture Specialist Published 1999 ATTRA Publication #IP110 |
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AbstractWorms can convert organic and agricultural wastes into safe soil amendments or ingredients for potting soil mixes. These "castings," are stable, yet biologically active, and very available to plants. The market for this valuable material, however, is not yet strongly developed. Systems can be designed to produce either the castings or the worms themselves as the commercial product. Table of Contents
IntroductionTo design a sustainable agricultural sector, the outputs from each production enterprise must become inputs to other enterprises just as in nature. Everything in the natural system is food to something else. We have not yet succeeded in mimicking this efficiency in our agricultural system. Many organic byproducts of agricultural production and processing are currently seen as "wastes" and thus become potential environmental hazards. Likewise, leaves, lawn clippings and restaurant food wastes have become problematical because their bulk fills limited landfill sites quickly. In some instances where the "output-becoming-input" model has been tried, we may have created other dangers. Currently wastes from poultry confinement systems are fed to other types of livestock although there is some public concern about this practice. Organic wastes can become safe soil amendments or substrate for the production of plants or feed for livestock when properly processed. Mushrooms and worms are two examples of products that can be raised on the wastes from other enterprises. Besides the primary product, the "wastes" are rendered more valuable and their volume has been reduced. Traditional composting is another way to reduce bulk and to improve the safety and general quality of organic wastes. The final result in both cases is a valuable soil amendment. Worms eat many types of organic waste materials and convert them into "castings." This material is highly valued as a soil amendment because it contains plant-available yet stable nutrients. It is biologically active as well and apparently contains plant hormones which can provide other advantages. If it is not applied back to the soil of the farm where it is generated, castings can be marketed to the landscape industry for use in landscape plantings or as a component of potting soil mixes. Another product is the worms themselves, which can also be marketed or further processed to become a livestock feed supplement.
For the farmer with livestock confined for all or part of the year and an accumulation of manure to safely dispose of, vermicomposting may be an enterprise to consider. A method requiring very little capital investment (although it will require timely management), vermicomposting can be integrated into the farming system and provide a separate profit center. An entrepreneur in a location where there are many confinement livestock operations can develop a vermicomposting business using the manure as a feedstock. Such a business would manage the worms as livestock themselves and then market the resulting products: vermicompost and worms. This has been done in both North and South Carolina, as a matter of fact (see boxes).
The Process and EquipmentVermicomposting is not really a type of composting. In fact, worms are likely to die if true composting, a heat-producing process, occurs. Vermicomposting can be seen rather as a form of livestock production. Many different materials can be used as feedstock for the worms. Animal manures are quite useable, most without any further preparation. Hog slurries, however, must be separated, and only the solids are fed to the worms. Poultry manures may contain excess ammonia and inorganic salts and so they must be processed to remove these substances which would be toxic to the worms. Plant residues, such as potato and brewery wastes, have also been tested as feedstocks for commercial systems. As in any livestock enterprise, it is critical to maintain optimal conditions. Moisture, pH, and aerobic conditions in the growing medium must be maintained to ensure healthy, growing worm populations. Profitable production depends on both growth and reproduction rates of worms as well as on the choice of a suitable species for the feedstuffs available. Different species have preferred ranges of temperature and moisture conditions. A review of the research on this subject is available in Edwards and Bohlen, 1996. (See Recommended Reading below) Vermicomposting methods can range from a worm bin in the kitchen for household scraps to large mechanized systems able to accommodate tons of organic material on a continuous basis. In general, these methods can be grouped into four types:
In the first two types of systems, thin layers of wastes (feedstuffs) are added at frequent intervals to the worm growing area until it reaches a given depth, usually about three feet. Worms are therefore always feeding in the top layers. Finished material may be removed from the bottom of the containers. Small-scale bed systems exploit the worm's preference for fresh feed to move worms from one side of a bed to the other. Finished material is removed from the other side of the bed. The aversion of worms to light or excessive heat can likewise be used to move worms from one area to another. Mechanical means can also be used. Screens fine enough for the castings to pass through, but too small for worms and cocoons are typically employed. Commercial separators are available. Please refer to the list of suppliers at the end of this publication. Currently, Eisenia foetida (known as redworm, red wiggler, or brandling worm) is the most common species used in vermicomposting. Optimal conditions for worm health and growth include maintaining the bed at 60º to 70º F (15º to 20º C), moisture at 80 to 90%, pH between 5 and 9 with oxygen present throughout the bed. Lower temperatures slow the vermicomposting process. Temperatures above 90º F are common in the composting of raw materials. It is therefore important to add thin layers when using uncomposted materials and to monitor temperature continuously. Moisture meters can ensure that worms, dependent on damp conditions to breathe through their skins, can thrive throughout the bedding material. In systems that control temperature, pH, and moisture, and employ the right type of worm, use enough of them, and balance feed rations, the production of compost can prove profitable. Such operations must be handled as enterprises even if they are part of an integrated farming system. They require attentive management and a certain amount of time. Some producers may not have time or money to create the highest yielding vermicompost system. They can still choose a slower, lower-input method and produce a valuable product. For others, the marketing required may prevent choosing the highly productive and potentially profitable controlled system. Nevertheless, vermicomposting offers opportunities for those whose operations and interests are well-matched. EconomicsThe economic value of products from vermicomposting confinement livestock wastes may not justify the cost of an intensive system, but the benefit to society as a whole might count them worthwhile. Practices such as applying too much manure directly on agricultural land and holding liquid wastes in poorly designed lagoons have, in some cases, resulted in very high nutrient levels in ground and surface waters. If confinement livestock operations are unable to ensure the protection of water and soil resources using current practices, processing the large amounts of wastes they generate becomes a community concern.
Composting and vermicomposting are two methods of converting these highly concentrated "wastes" into valuable resources. Whether these benefits can be translated into profits through vermicomposting depends upon many factors. In any business or farm enterprise, the anticipated return on investment must be carefully considered before one commits to it. For large scale vermicomposting units, operating costs are the most important consideration. On the other hand, for smaller units the capital expenses associated with setting up the system are the most expensive item. For a medium sized livestock operation, a low tech system requiring skilled management may make the most economic sense, if operations can be planned so that peak labor seasons can be coordinated. Economic viability depends primarily on the price received for the compost. Marketing this product is therefore a critical activity. Worms sold for bait are an additional source of income (see sample 1994 worm production budget). They generally bring higher returns than worms processed and sold as a protein feed supplement for poultry or fish. However, the market requires only a limited number of bait worms. Some additional worms can be sold to other people interested in vermicomposting or baitworm businesses if this market is developed. Commercial vermicomposting is just beginning in this country. San Diego, California, has employed worms to convert part of its organic waste stream into useable products. The castings are reportedly in high demand. In Oregon, a research/demonstration project has become a thriving business. The Oregon Soil Corporation uses a continuous flow reactor. A large urban hospital in Ontario likewise has been using worms to process some of its waste stream for several years. Countries other than the US have been researching and using commercial systems for a decade or more. Cuba, in particular, has relied on reusing its organic wastes since its supply of petroleum has been curtailed. Vermicomposting has been investigated as a way to convert some agricultural wastes into a soil amendment for more than ten years. Currently France, Germany, Italy, Japan, Hong Kong, India, Australia, and many countries in South America have research or commercial vermicomposting projects underway.
Further InformationListed below are several key reference books as well as publications, an association, and sites on the Web which address the subject of vermicomposting. In addition, Biocycle will publish Manual on Vermicomposting, edited by Clive Edwards, one of the world's foremost writers on the subject, in 1999. This book will likely be worth obtaining when available. Recommended ReadingBogdanov, Peter. 1996. Commercial Vermiculture: How to Build a Thriving Business in Redworms. Vermico, Merlin, OR. p. 64-66.
Edwards, C.A. and E. Neuhauser (eds.). Earthworms in Waste and Environmental Management. SPB Academic Publishing BV, The Hauge, The Netherlands. Available for $110 ppd. from:
Edwards, C.A. and P.J. Bohlen. 1996. Biology and Ecology of Earthworms (3rd ed.). Chapman & Hall, London. 426 p. Lee, K.E. 1985. Earthworms: Their Ecology and Relationships With Soils and Land Use. Academic Press, NY. p. 173-182, 205-213. Satchell, J.E., (ed.). 1983. Earthworm Ecology: From Darwin toVermiculture. Chapman and Hall, NY. 495 p. Further ReadingHolcombe, Dan. n.d. Blueprint for a Successful Vermiculture System. Oregon Soil Corporation, 1324 Beaver Lane, Oregon City, OR 97045.
Bhawalkar, Uday. n.d. Vermiculture Ecotechnology. Bhawalkar Earthworm Research Institute, Pune, India. 380 p. Worm Book SellersArlan & Sons Lewis Publishers Rodale Press Shields Publications Van Arsdale's Worm Sales Periodicals with Vermiculture Information Worm Digest VermiCo WormWise News Composting Rules: A Summary of Legislative and Regulatory Issues BioCycle: Journal of Composting & Recycling Waste Age Recycling Times Resource Recycling Worm Web SitesThe Compost Resource Page: Large-Scale Composting The Compost Resource Page: Vermicomposting Internet ListSend message to LISTSERVE@maelstrom.stjohns.edu with following command in the body of the email: SUBSCRIBE WASTENOT FIRSTNAME LASTNAME. Worm AssociationGlobal Vermiculture Association Consultants and Sources of Worms and EquipmentEnviro-Ganics Environmental Earthworm Projects, Inc. Oregon Soil Corporation Original Vermitech Systems, Ltd. Resource Conversion Corporation Vermi-Organic Digesters The Worm Concern Compost Cover SuppliersAutrusa Co. Texel References
Worms for Composting (Vermicomposting)
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