The Western Isles council is in the process of installing a new waste collection system, which will see residents using a bin for combined kitchen, garden, paper and cardboard waste. This material will be sent to the plant from October 2006.
The facility might also take seafood waste from the fishing industry in the Outer Hebrides, which is about 50km from mainland Scotland.
The new anaerobic digester, which is being built by international company Earth Tech in Stornoway on the Isle of Lewis, is part of a new 10 million integrated waste management site.
The council is collecting organic waste in one bin rather than making separate collection for paper and card recycling, because links to recycling infrastructure from the Island are poor.
Technology
When finished the plant which will use anaerobic digesters from technology company Linde, to produce a green gas and a good quality compost.
Anaerobic digestion uses a biogas engine to draw off gas from the process to create renewable energy. The Western Isles plant will in part use the gas to power the whole process, and any excess is expected to go to the national grid.
As well as this, the plant will produce a moist digestate that can then be mixed with more woody material to give it structure, before it goes through an open windrow system to produce the compost.
The plant will also employ mechanical sorting techniques and is likely to take a portion of the Island’s residual waste too through a combination of MBT and AD. AD is a relatively new technology in the UK, with Shropshire and the Western Isles among the only councils that have commissioned AD plants.
Earth Tech
Tony Lewis, business development manager at Earth Tech believes construction of the plants are virtually running neck and neck. The Shropshire plant is slightly smaller and is being built by a relatively new company, Greenfinch (see letsrecycle.com story).
Mr Lewis said that the Western Isles project was the company’s first in the UK for food waste, although the company has built plants for the water treatment sector.
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Earth Tech is partnering a number of waste management companies in their contract bids with local authorities: “We were working with one of the companies going for the Gloucestershire contract before the council sadly pulled the process,” explained Mr Lewis.
“We are also involved in a few other deals which would include a mixture of MBT and AD in contracts treating 100,000 tonnes of waste a year,” he added.
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