**6. References**


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production and natural gas grid injection, have been presented as well as the use of parasitic energy, options for biogas production enhancement through waste pre-treatment (mechanical, chemical, physical, etc.) and treatment of residues of anaerobic digestion, which may have an important impact on the environment. Special attention is given to further treatment of digested solid residues as well. Due attention is paid to aerobic stabilization processes (open and closed composting), taking into account physical form of

The authors express acknowledgements to Slovenian biogas producers and to the Slovenian Science and Research Agency, whose support in anaerobic digestion and waste treatment

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Manag. 27, 1317-27


**2** 

*1Spain 2Austria* 

*1Universidade de Vigo 2University of Innsbruck* 

**Vermicomposting: Composting with** 

Jorge Domínguez1 and María Gómez-Brandón2

**Earthworms to Recycle Organic Wastes** 

The overproduction of organic wastes has led to the use of inappropriate disposal practices such as their indiscriminate and inappropriately-timed application to agricultural fields. These practices can cause several environmental problems, including an excessive input of potentially harmful trace metals, inorganic salts and pathogens; increased nutrient loss, mainly nitrogen and phosphorus, from soils through leaching, erosion and runoff; and the emission of hydrogen sulphide, ammonia and other toxic gases (Hutchison et al., 2005). However, if handled properly, organic wastes can be used as valuable resources for renewable energy production, as well as sources of nutrients for agriculture, as they provide high contents of macro- and micronutrients for crop growth and represent a low-cost

The health and environmental risks associated with the management of such wastes could be significantly reduced by stabilizing them before their disposal or use. Composting and vermicomposting are two of the best known-processes for the biological stabilization of a great variety of organic wastes (Domínguez & Edwards, 2010a). However, more than a century had to pass until vermicomposting, i.e. the processing of organic wastes by earthworms was truly considered as a field of scientific knowledge or even a real technology, despite Darwin (1881) having already highlighted the important role of earthworms in the decomposition of dead plants and the release of nutrients from them.

In recent years, vermicomposting has progressed considerably, primarily due to its low cost and the large amounts of organic wastes that can be processed. Indeed, it has been shown that sewage sludge, paper industry waste, urban residues, food and animal waste, as well as horticultural residues from cultivars may be successfully managed by vermicomposting to produce vermicomposts for different practical applications (reviewed in Domínguez, 2004). Vermicompost, the end product of vermicomposting, is a finely divided peat-like material of high porosity and water holding capacity that contains many nutrients in forms that are

Vermicomposting is defined as a bio-oxidative process in which detritivore earthworms interact intensively with microorganisms and other fauna within the decomposer community, accelerating the stabilization of organic matter and greatly modifying its

**1. Introduction** 

readily taken up by plants.

alternative to mineral fertilizers (Moral et al., 2009).

