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Article by Councillor Stephen Quigley for the newsletter of the Mundham and Runcton Residents Association (MARRA). Reviewed by Langmead Farms, KPS and the Environment Agency.
March 6, 2008
In February 2003 Langmead Farms obtained planning permission from West Sussex County Council to operate a windrow based green waste composting facility at Walnut Tree Farm, Runcton, Permission was given for five years from the date on which waste was first delivered or six years from the date of planning consent. The Environment Agency (EA) issued a waste management licence in November 2003 with a production limit of 25,000 tonnes per annum. The site opened in September 2004.
The site is managed on behalf of Langmead Farms by a specialist composting site management agency, KPS. The green waste comes from local landscape gardeners and waste management companies who bring waste from civic amenity sites in West Sussex and Surrey. About 12 to 15 per cent comes from Nature’s Way Foods packing house down the road consisting of lettuce trimmings and reject lettuce heads.
If any one load of waste received on site contains more than five per cent contaminating material (for example, food waste, plastic or general household waste) the load is rejected and removed from the site. Contaminating material below this threshold is removed by hand before processing. The quantity of material accepted at the site that ends up in landfill is less than one per cent by weight.
The process takes 12 weeks. On delivery at the eastern end of the concrete slab, green, mostly garden waste, of which there are around five to 15 deliveries every weekday, fewer on Saturday mornings between 08:00 and 13:00, is shredded. Over one to two weeks one complete windrow of 500 to 700 tonnes is built up. During this sanitisation phase, pathogens, eg. ecoli, and weed seeds, are broken down by the heat generated within the windrow and by bacteria.
A given windrow will be turned about eight times over the next 10 weeks as it moves from the eastern to the western end of the site. The purpose of turning is to let air into the windrow and assist the decomposition process. The temperature is monitored weekly to check it is within the range of 65 and 75 degrees Celsius, so as to ensure maximum bacteria activity. Moisture levels are also monitored and water added if necessary. The water comes from the lagoon that collects run off from the delivered waste loads.
At the end of the period the windrow is screened with a mesh of 25 mm. What falls through constitutes the finished product. What is caught, about five percent, is added to new deliveries and goes through the process a second time. All the product is used by Langmead Farms on its farms in West Sussex.
The problem of odour began in March 2006. The first complaint was received by the EA in May 2006. In the summer of that year as a result of my intervention, the Environment Agency, West Sussex County Council, Langmead and KPS agreed action plans that included investment in new equipment for shredding and turning. There was some improvement but odour, an unpleasant sweet pine type, continued to reach residents in Merston and Marsh Lane in 2007. Weather conditions, temperature and wind direction are factors but not major ones.
Last summer and fall I had meetings with the Environment Agency and KPS to improve odour monitoring and experiment with so-called inoculants that produce a separate odour to suppress the composting odour. The position at time of writing is that incidents are much less frequent than in the past but we wait until the spring when the volumes processed increase and the temperature rises, to measure whether the improvement is sustained.
Under the terms of its waste licence the waste operator is required to ensure the site shall be free from odours at levels as are likely to cause pollution to the amenity of the locality outside the site boundary, as perceived by the EA.
Green waste collected from Chichester District residents is processed by the Woodhorn Group at Tangmere. This operation too had initial problems with odour but made changes to the process to reduce the amount of turning.
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