Worm composting for a typical household usually involves a small storage tote or wooden bin with bedding and a couple of pounds of red wiggler worms, or Eisenia fetida. Large-scale worm composting requires a good stream of organic materials for the red wigglers to feed on. Thus, worm composting on a grand scale typically occurs either on farms that raise cattle, horses, sheep, poultry or rabbits to provide the manure needed or nearby in an industrial setting. Large-scale worm composting can also take advantage of commercial food-processing wastes or coffee pulp. (See References 1, page 8)
While home systems employ just a shallow lidded box, large-scale worm composting relies on one of three systems: windrows, beds or bins, or flow-through reactors. Windrows are essentially long rows of organic materials that the worms work through. These need to be watered or covered to retain moisture, writes researcher Glenn Munroe of the Organic Agriculture Centre of Canada in "Manual of On-Farm Vermicomposting and Vermiculture." (See References 1, page 19) Beds or bins can be of any material or shape that allows red wigglers access to shallow organic materials, such as a cement floor with cinder blocks stacked three high to create the bin. Flow-through reactors are raised rectangular boxes with bedding and organic foodstocks, where the worms are not disturbed in the bed as food is added to the top surface. They feed near its surface, and a breaker bar moves along a bottom grate to harvest the compost. (See References 1, page 24)
The method used determines how soon organic materials are converted to vermicompost. Low-tech windrows can take six to 12 months to process, writes Jim Jensen of Pennsylvania-based Environmental Credit Corp. and co-author of "The Commercial Potential and Economics of Vermicomposting," a chapter in the text "Vermiculture Technology." Earthworm bins take two to four months, they found, and fully automated computer-controlled systems, such as the more elaborate reactors, one to two months. (See References 2, page 314)
The largest vermicomposting facility in the eastern U.S. in 2011 is RT Solutions in Avon, New York, which makes worm compost sold under the name of Worm Power (see Resources 2) . The company reported selling more than 400,000 lbs. a year of bulk and packaged worm compost and liquid extracts in 2010, reports Janice Sitton in "Biocycle" magazine (see References 3, page 60). Humbler efforts are underway in Guatemala, where Maria Rodriguez, founder of Byoearth, introduced worm composting to 20 women living near a city dump. The project redirects waste from the dump and coffee pulp and feeds it to a population of 10 million compost worms, Sitton reports. (See References 3, page 63)
Large-scale worm composting is expected to meet the challenge of recovering large volumes of organic material via advances in technology, Jensen notes. Future vermicomposting technology will move further along the direction of automated feeding and harvesting, continuous flow for consistent production and controlled aeration, as well as automated moisture control. (See References 2, page 315)
An award-winning writer and editor, Rogue Parrish has worked at the Washington Post, the Baltimore Sun and at newspapers from England to Alaska. This world adventurer and travel book author, who graduates summa cum laude in journalism from the University of Maryland, specializes in travel and food -- as well as sports and fitness. She's also a property manager and writes on DIY projects.