Donarbon waste management visit and lecture

This was a fascinating visit to a world leading recycling plant.  Thirty members and guests, thoroughly enjoyed their time over the course of a working morning at the Donarbon Waste Management site at Chittering in Cambridgeshire.

Karen Brenchley, the Education Coordinator talked us through the processes that turn our county’s waste into useful resources and drove us on a tour identifying the areas of activities.  Household waste is processed in the Mechanical Biological Treatment (MBT) where it is sorted through a series of 66 convey belts, and sorted on size, weight and composition.  Ferrous and aluminium metals, stones, glass and plastics are all removed, and the resulting mass is shredded, watered and ‘composed’ in sheds for periods of 7 weeks.  The out put from these sheds, which are monitored by the environmental agency and researchers from the OU, are an improved material for landfill as they decompose more readily.  Experimental work is underway to utilise this material as a biofuel.  Other areas on the site; sort; wood, building masonry, soil, green waste from professional gardeners and household garden/kitchen waste which are all collected for processing.  The household garden/kitchen waste is composed in a process called In-vessel composting (IVC), that raises the temperature of the compost uniformly to  60-70 degrees C and so inactivates the vegetative stages of potentially pathogenic, residual uncompostible items are then removed and the resulting soil-like material ismade available to the general public as compost for gardening.

Chris Barry FSB, from Anchor gave a lecture on ‘The Biology of Waste’ in which he highlighted the under-utilised resource of waste material.  From his experiences in advising third world countries on their management of waste material he identified ways to hasten the microbial breakdown of celluloses to more simple organic compounds, such as methane and butyric acid. He spoke of the dangers of leachates and the products of anaerobic metabolism and the risks of the multiplication of pathogens. He mentioned the benefits of removing metals such as toxic cadmium and the rare precious metal, rhodium. The risks associated with methane production, which can cause flash burns in a waste dump were discussed, where scavengers are routing for usable material, and of nitrous oxide production, a more potent greenhouse gas than methane.

Finally with our new blue bins in place across the county, we asked about the recycling of mixed recyclable material and were told that the best classes of this material is where there is a sorting at source, ie the home and discovered that aluminium cans, glass, plastic and cardboard command a greater price when collected as separated entities. So I think in future I will continue to collect these items separately and use my local glass/aluminium/plastics repository!

 Pictures courtesy of Alan Wainwright

Liz Campbell October 2011