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| Green waste materials, which meet the Middleton site waste acceptance criteria are weighed into the site prior to being checked for any items of contamination. Contaminant items would be removed for landfill disposal. Materials are then shredded using a large mechanical shredder before being formed into windrows where the active composting process takes place. The composting process occurs due to natural biodegradation mechanisms involving microbes present in the incoming waste feedstocks. The objective of the composting process is to optimise growing conditions for these microbes so that they maximise the aerobic breakdown of the materials into stable products. The initial phase of the composting process is know as the Sanitisation Phase and during this phase high temperatures can be generated by the actions of a specific group of microbes, for example temperatures of 65oC can be achieved. These high temperatures are essential for making compost products safe as any pathogenic organisms (for either humans or plants) are killed off. Also any weed seeds present would be inactivated by this heat. Optimum conditions for the beneficial microbes are controlled by turning the compost to release heat or introduce more air, by adding water where necessary or by amending the mixture of materials. During this phase the compost is monitored daily to check temperature and moisture levels and to determine suitable control actions. This initial Sanitisation Phase can last for around 4 weeks. After sanitisation has been achieved, materials would be transferred into a less actively managed phase called Stabilisation. During the Stabilisation Phase, different groups of microbes grow and develop to further breakdown the compost materials. Temperatures will fall slowly towards background levels and although materials are still monitored regularly, actions such as turning are required on a less frequent base. After a period of between 2-6 months the compost would be classified as mature and the products would be stable with microbial proceeding at a reduced pace, similar to natural background levels. Products can then be released for sale. |
William Tracey Limited, Middleton Composting Facility, Loch Libo Road, Lugton by Beith, Ayrshire, KA15 1HZ.
Telephone: 01505 850116, Fax: 01505 850753