What is vermicomposting?
According to Arancon and Edwards (2006), it is the non-thermophilic process by which organic materials are converted by earthworms and microorganisms into rich soil amendments with greatly increased microbial activity and nutrient availability.The term has its origin from vermis, the Latin word for worm. The term is also used to refer to the technology of converting raw organic materials into organic fertilizer, called vermicompost, mainly through microbial action and the use of certain species of earthworm. In addition, the technology is applied in waste management by which organic “wastes” are recycled and made available for plant growth.
This process is inseparable from vermiculture or the culture of earthworms. In vermiculture, the earthworm is the primary product while the vermicompost is only a by-product.
But the primary object of the vermicomposter is the production of vermicompost, a special type of compost, with earthworms as secondary product. In vermicomposting, the organic materials must be chosen with care or mixed in the right proportions and the compost bed must be provided with optimum conditions for the growth and reproduction of earthworms so that they will be more efficient in their feeding of the organic materials and producing excreta called vermicast.
Composting, which refers to the controlled decomposition of organic materials, has been used by farmers and gardeners since prehistoric times to recycle wastes into products that enhance plant growth (Trautmann and Krasny 1997).
Charles Darwin, the English naturalist who made waves in the scientific community with the publication of his “Of the Species and the Descent of Man,” conducted a comprehensive study of burrowing earthworms. In 1881, he published his last and final book “The Formation of Vegetable Mould, Through the Action of Worms, With Observations of their Habits” which reported in detail how these organisms feed and convert organic materials, mainly leaves, to castings which favor plant growth.
In the 1950s, vermiculture was started in the United States for the production of fish baits. In the 1980s, the United States and United Kingdom started using earthworms to produce vermicompost from organic wastes. In the Philippines, the production of vermicompost and vermimeal, or earthworm meal, started in 1979 (Guerrero 2009). But it was only in 1982 that the composting earthworm called African night crawler (ANC) was introduced into the country (Guerrero et al. 1984).
The publication of the “Proceedings of a Workshop on the Role of Earthworms in the Stabilization of Organic Residues” in 1981, 100 years after Darwin's study, is responsible for the accelerated interest on the use of earthworms in breaking down organic wastes within and outside of the United States. Roy Hartenstein in the US and and Clive A. Edwards in the U.K. spearheaded the research on vermiculture in the 1980s (Edwards 2006).
As of 2004, Edwards (2004, cited by Edwards and Arancon 2006) reported that commercial vermicomposting projects have been developed in many countries such as England, France, the Netherlands, Germany, Italy, Spain, Poland, the United States, Cuba, Mexico, the Bahamas, China, Japan, Philippines, India and elsewhere in Southeast Asia, as well as Australia, New Zealand, American Samoa, Hawaii, and many countries in South America.
On November 16-18, 2005, the International Symposium-Workshop on Vermi Technologies for Developing Countries was held in the Philippines.
Vermicomposting methods vary according to various factors such as location (indoor, outdoor), intensity of care and scale of production (backyard, commercial), systems used (windrow, worm bins, bioreactors), methods of feeding and preparation of organic materials (gradual, batch, mesophilic, combined thermophilic and mesophilic composting).
For backyard batch composting following the windrow or outdoor pile method, it is common to combine thermophilic (high temperature) composting in which a maximum pile temperature of about 60-65°C is targetted. This is referred to as the pre-vermicomposting stage during which complex organic compounds are degraded by microorganisms. At the end of this thermophilic stage, the temperature of the pile gradually drops and the composting process becomes mesophilic (moderate temperature). This signals the right time to commence the second stage in which the right species of earthworm is introduced.
As a practical guide in vermicomposting, the following procedure (thermophilic + mesophilic process) is provided:
1. Prepare the following materials or provide at the right time: carbon- and nitrogen-rich organic materials, spade, ground space, hollow blocks, stakes, plastic sheets or used sacks, water and water sprinklers, shading materials, nylon net or any substitute to cover the beds, and composting earthworms (e.g. ANC). Nitrogen-rich substrates refer to animal manures, legumes, and fresh grass clippings, while others, particularly those colored brown and dry, are generally classified as carbon-rich substrates.
2. Mix carbonaceous with nitrogenous organic materials at the right proportions to obtain a C:N ratio of about 30:1. For example, rice straw and fresh manure are mixed at about 25:75 ratio by weight. But for practical application, a 1:1 or 50:50 ratio by volume can be tried as basis in mixing bulky carbonaceous materials (e.g. dried grasses) and manures.
3. Prepare the vermi bed by spreading plastic sheets or used sacks on the ground to prevent mixing of the soil with the compost during harvesting. Pile two layers of hollow blocks in square or rectangular pattern. Secure the blocks by sinking stakes through the holes. Remove completely growing vegetation sorrounding the bed and sweep away plant debris that may serve as food and induce the earthworms to migrate outside. Provide shade.
4. Fill the bed with the organic materials and water sparingly. The size of the pile can vary but in general, a volume of at least 1 cubic meter (1 m3) is desired to allow thermophilic heating. A pile 1 m wide, 2 m long and 0.5 m high will have this volume. To conserve moisture and heat, the pile is covered from the top to the sides with plastic sheets or any substitute materials.
5. Wait for at least 15 days for the thermophilic process of composting to end. This process is characterized by a rapid increase in temperature of the pile (it can be checked manually with an open palm on top of the pile) followed later by a gradual decrease. When temperature approaches ambient temperature (<35°C, the height of the pile also subsides), remove the covering. Sprinkle with water if necessary, then commence vermicomposting proper by introducing the right species of earthworm.
6. Stock the partially decomposed organic materials with composting earthworms, e.g. ANC, by releasing them on top of the pile. The earthworms will immediately move downward. A stocking rate of about 500 g of earthworms is sufficient for an original pile of 1 m3 but it can be lesser or more, depending on availability. Heavier stocking rate will mean faster rate of vermicast production.
7. Mulch the pile with coconut coir dust or grasses to prevent excessive loss of moisture. Then cover with nylon net or any substitute material like coconut fronds to serve as barrier against birds and other earthworm predators. Maintain sufficient moisture and aeration throughout the composting process.
8. Harvest the vermicompost as needed or when only a few organic materials remain intact. Use the earthworms for another round of vermicomposting. (click on to read harvesting methods)
ARANCON NQ, EDWARDS CA. 2006. Effects of vermicompost on plant growth. In: Guerrero R.D. III, Guerrero-del Castillo MRA (eds.). Vermi Technologies for Developing Countries. Proceedings of the International Symposium-Workshop on Vermi Technologies for Developing Countries. Nov. 16-18, 2005, Los Baños, Laguna, Philippines. Philippine Fisheries Association, Inc. p 32-65.
DARWIN C. 1881. The Formation of Vegetable Mould, Through the Action of Worms, With Observations of their Habits. London: John Murray. Retrieved May 27, 2011 from http://darwin-online.org.uk/pdf/1881_Worms_F1357.pdf.
EDWARDS CA. 2006. Foreword. In: Guerrero R.D. III, Guerrero-del Castillo MRA (eds.). Vermi Technologies for Developing Countries. Proceedings of the International Symposium-Workshop on Vermi Technologies for Developing Countries. Nov. 16-18, 2005, Los Baños, Laguna, Philippines. Philippine Fisheries Association, Inc. p. iv-v.
EDWARDS CA, ARANCON NQ. 2006. The science of vermiculture: the use of earthworms in organic waste management. In: Guerrero R.D. III, Guerrero-del Castillo MRA (eds.). Vermi Technologies for Developing Countries. Proceedings of the International Symposium-Workshop on Vermi Technologies for Developing Countries. Nov. 16-18, 2005, Los Baños, Laguna, Philippines. Philippine Fisheries Association, Inc. p. 1-30.
GUERRERO RD III. 2009. Vermicompost and Vermimeal Production. MARID Agribusiness Technology Guide. 22 p.
GUERRERO RD III, GUERRERO LA, CARGADO AU. 1984. Studies on the culture of the earthworm, Eudrilus euginae, and its use use as feed for Macrobracchium idella and fertilizer source for Brassica compensis. Trans. Nat. Acad. Science. 6:33-40.
TRAUTMANN NM, KRASNY ME. 1997. Composting in the classroom: scientific inquiry for high school students. Retrieved May 29, 2011 from http://cwmi.css.cornell.edu/compostingintheclassroom.pdf.
(Ben G. Bareja, July 2011)