Vermicomposting: An alternative method for organic waste management

by Dr William Stiles: Farming Connect Knowledge Exchange Hub, IBERS, Aberystwyth University

Organic or green waste generation (materials including food, plant or animal wastes, such as manure) can be a major problem for agricultural businesses, which can be difficult and costly to manage effectively. Vermicomposting (sometimes referred to as a wormery) is an alternative method for organic waste management, which can simultaneously recycle valuable resources such as nutrients.

an effective vermicomposting system can rapidly reduce the burden of organic agricultural waste whilst producing value added products such as fertiliser, soil conditioner, and earthworm biomass.

The vermicomposting process is similar to traditional composting, in that organic waste is broken down through biological decomposition in an aerobic environment to produce stabilised organic fertilizer. Unlike composting however, vermicomposting includes action by earthworms as well as microorganisms, which acts to biodegrade organic waste at a faster rate.

The actions of earthworms in the vermicomposting process are both physical and biochemical. Earthworms break up the organic material through physical action, which also increases turnover and aeration, increasing the activity rates of other microbial organisms. Through active digestion the organic material is also transformed by enzymatic processes, which acts to recycle important nutrients into forms that are readily available for plant uptake.

Vermicomposting systems can be designed at small or large scale, but it is important to consider certain factors in order to achieve maximum potential. Earthworms are the essential component of this system, and these organisms will require a specific environment to thrive. For instance, earthworms require damp environments to maintain activity rates, as these organisms breathe through their skin.

Earthworm activities are also significantly affected by temperature; should temperatures drop below 10oc, reproduction and metabolic rates will decline. The system must be aerated, as these organisms require oxygen, which is typically achieved through manual turning. However, this action should be undertaken sensitively as earthworms are highly photosensitive and prolonged exposure to light will have adverse effects.

The nature of the organic waste applied also needs to be considered. The carbon to nitrogen ratio of feed material will affect earthworms when this is either too high or too low, by influencing growth and reproduction rates. Feed material pH is also important; whilst earthworms can process most organic materials, certain substances, such as those with pH <5, may require pre-treatment or bulking with other organic materials to avoid harm to these organisms.

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