The “revolutionary” municipal solid waste aerobic digester is a 1million pilot project that will deal with 5,000 tonnes of unsorted waste a year that would otherwise have gone to landfill.
 John Wearmouth, chairman of CDENT, shows Tony Blair the resulting compost from the digester |
Prime Minister Tony Blair, who opened the plant in Thornley on Friday, said: “This aerobic digester is at the cutting edge of everything that is happening in the country and the rest of Europe. It’s something we can be proud of.”
He added: “The composting process is a fantastic innovation and there are big lessons to be learned for the rest of the country.”
Funding for the plant has come from the County Durham Environmental Trust, and chairman John Wearmouth welcomed the Prime Minister's involvement. He said: “The presence of the Prime Minister here today underlines the importance of what is being achieved in pushing forward the frontiers of waste processing in County Durham.”
Process
Operated by Premier Waste Management, the plant will take mixed municipal waste direct from refuse collection vehicles, processing it with a slow-speed shredder that has a high torque designed to cope with tough, tangled materials such as carpet and hard items including brick and metal. The waste is then weighed and monitored for moisture content before entering the aerobic digester for composting.
“The digester aims to replicate the optimum environment for rapid composting to take place,” explained Karl Shaw, manager of manufacturers CPS Civic Ltd. “At each level, the mixture can be agitated and air or moisture added. Once it achieves a certain level of decomposition, it passes through to the next level to compost further. The gases that result are removed by a fan and are treated through a scrubber spray and biological filter system, so eliminating odours from the digester.”
The output material from the digester is then passed through a trammel screen to remove over-sized pieces, particularly plastic, and other non-compost material is also removed. Researchers at Newcastle University are currently looking into uses for the compost that the process will produce, but it is expected that up to 50% of the original waste, by weight, will be usable.
If the pilot project is a success, the aim is to develop full-scale plants capable of handling over 100,000 tonnes of waste a year unless it is decided that a larger number of low-capacity plants will avoid the need for large-scale waste transportation.
Chris Tunstall, Director of Environment and Technical Services at Durham County Council, said: “The opening of the digester today shows that the County's Strategy for dealing with waste is working. We have adopted a strategy, which avoids incineration and concentrates on waste minimisation, recycling and composting. We hope that we will raise our performance to meet national targets and then to exceed them in later years.”
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