Levenseat Ltd, Composting

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Levenseat Ltd

Waste Management Specialists

Text Box: Composting Composting is a technology with roots in ancient history and the general principles which govern modern composting are the same as those applied by our Pictish and Celtic ancestors, namely: Composting is an organic process in which we seek to create an optimum living environment for a population of micro-organisms. The principal requirements of these micro-organisms are a range of nutrients, oxygen and warmth. At Levenseat we meet these requirements by: We select a mix of materials to compost which provide a balance of nutrients – the principal elements of which are Carbon (C) and Nitrogen (N) with an optimum mix having a C:N ratio in the range between 25:1 and 40:1. We incorporate in the mix shredded wood which helps to maintain an open structure, allowing percolation of air and venting of carbon dioxide. We pile the compost mix into trapezoidal blocks sitting on a concrete pad. We install under the compost block a system of perforated pipes which are used to suck air through the compost block. The compost is turned on a regular basis using specialist compost turning equipment. This re-opens the structure, releases pockets of carbon dioxide and re-mixes the nutrients. The temperature of the compost is monitored daily. Heat is generated in the compost by the metabolism of the micro-organisms and temperature is largely controlled by an optimum mix of nutrients and by adjusting the aeration regime. Insufficient air results in a decrease in biological activity and hence of temperature – although too much air can also have a cooling effect. Compost remains in the blocks for about 6 weeks at the end of which it is screened to remove larger sized particles (which are re-introduced into the next batch). It is then allowed to mature for a further 3 weeks after which it is ready for use as valuable soil conditioner. Each year at Levenseat we compost in this manner some 30,000 tonnes of materials including green waste (prunings, grass cuttings), sawdust, a range of bi-products from the food industry (eg potato peelings) and organic industrial by-products (eg limed fleshings from tanneries). Composting operations are carried out on a concrete pad which ensures that any rainfall which becomes contaminated by washing through the compost is collected and treated in the Waste Water Treatment Facility The compost aeration system (which sucks air through the compost) is powered by a diesel fan with a capacity of 50,000 m3 per hour. The extracted air is vented into a bio-filter which removes any odours which are extracted from the compost. Like the compost, the bio-filter is an organic system. It is constructed as a bed of wood chips approximately 3m deep. The air is introduced at the bottom of the bed and allowed filter upwards through the wood chips. A population of micro-organisms is established on the surface of the wood and this extracts and uses as nutrients the organic molecules which could result in emissions of odour.

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