Scotland to open anaerobic digestion facilities in 2010

Three anaerobic digestion facilities are opening in Scotland next year providing food manufacturers with an alternative to landfill for their waste.

The first of the facilities - all run by Scottish Water Waste Services - is scheduled to open in the spring in Deerdykes, Cumbernauld, with a further two sites opening later in the year at Renfrewshire and Ayreshire.
The Deerdykes facility will be able to handle 30,000t/year of ‘category three’ food waste (which includes packaged waste but excludes fallen stock and high risk material from carcasses) in a continuous process. It will generate biogas and a liquid digestate.
The digestate will be used as a liquid fertiliser in the summer months and can be dewatered to produce a solid cake fertiliser in the winter, said business development manager Donald MacBrayne.
The biogas will be burned to generate electricity and heat or cleaned up for use as a vehicle fuel, he said. “Some of the heat will go back into the process [which involves a fermentation at 37 degrees centigrade and pasteurisation at 70 degrees centigrade] and some surplus heat will go to the adjacent industrial estate. “We’re in advanced talks with a very well-known Scottish soft drinks company.”
The capital costs and technical complexity associated with anaerobic digestion meant it was “not for the faint hearted”, said MacBrayne. However, it was becoming increasingly appealing to manufacturers as landfill costs continued to escalate. “You’ve got to have the right site - you need to be able to utilise the heat as well as the electricity.”
Charges varied depending on quantities and what arrangements manufacturers opted for, said MacBrayne. “We can pick up your waste or you can deliver it to us. It’s very competitive compared to landfill, but companies also want to do this for corporate social responsibility reasons.”
Landfill costs are currently £40/t plus a gate fee of up to £25, with costs increasing by £8/t every year until 2013.