Thursday, July 17, 2008

Report: Energy-from-Waste and Anaerobic Digestion (AD) is the Most Sustainable Option

Scottish waste policy set to lean towards CHP

Two reports which will help form the "cornerstone" of the Scottish Environmental Protection Agency's policy on the thermal treatment of waste have both advocated the use of combined heat and power.

The studies, which were published by SEPA in tandem yesterday (July 3), come in the wake of the Scottish Government's opposition to larger Energy-from-Waste facilities (including anaerobic digestion) which it views as "inefficient" (see story), and, perhaps reflecting this, they both recommend "small-scale" rather than large plants.

"There is recognition that waste at any level has an inherent value and that value can be recovered through the generation of heat and power."

John Ferguson, SEPA

Research from both reports is currently being used to revise SEPA's Thermal Treatment Guidelines, which are set to be published in September 2008, and are described by the agency as "the cornerstone" of its policy on energy from waste.

"The guidelines will ensure that thermal treatment in Scotland enables the recovery of energy efficiently and does not impede waste prevention and recycling," SEPA explained.

While examining different aspects of waste management, both reports arrive at the conclusion that providing combined heat and power through Energy-from-Waste and anaerobic digestion (AD) is the most sustainable option available for various waste streams.


Published by consultancy AEA Environment and Energy, the first report, entitled 'The Evaluation of Energy from Biowaste Arisings and Forestry Residues in Scotland', assesses the energy value within the country's garden, kitchen and food waste, and related wastes.

And, it discovered that, of the 13.73 million tonnes of this kind of waste produced in Scotland each year, 9.634 million tonnes of it was "technically suitable to be processed in an anaerobic digestion or thermal treatment plant to obtain energy".

After analysing the energy content of these biowastes, the report calculated the potential for conversion to "useful" energy (heat or electricity) and, using combined heat and power as the preferred option, discovered that there is the potential for 2,285,200 megawatt hours (MWh) of electricity and 8,784,1000 MWh to be produced.


The report estimated that 741 AD and 228 thermal treatment plants, "allowing localised energy production and waste treatment", would be required to achieve this level of electricity and heat production, and also claimed that it would offset up to 5.6% of Scotland's total net greenhouse gas emissions.

While it did not examine economic issues, the report concluded that: "Given the substantial technical potential, even if a modest proportion of this were to be economic, energy from waste has a material contribution to make to Scotland's energy supply."

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