The Energos technology transforms waste into a gas phase which is subsequently combusted to produce both heat and electricity.
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The technology was developed in Norway in the 1990s in conjunction with the Norwegian government to provide a low emission, community-scale process that could accept waste with minimum pretreatment and produce energy. This led to six commercial plants in Norway and one in Germany, with the technology now having more than 700,000 hours of operation in total.
The process initially converts municipal solid waste (MSW) or commercial and industrial waste into a syngas which is subsequently combusted in a separate chamber before the resultant heat is used to generate steam. The steam can be used to supply heat, but is more typically used in a turbine to produce electricity.
As an advanced conversion technology (ACT), the Energos process qualifies for Renewable Obligation Certificates (ROCs) for the electricity produced from the renewable content of the waste.
The incoming waste requires only minimal pre-treatment, which minimises operating costs, and produces very low emissions to atmosphere due to the two-stage process. In particular, the nitrogen oxide emissions are very low and require no additional abatement, unlike most thermal processes.
Typically, in the UK, the waste requiring processing will be residual waste which has already had recyclable materials removed. All three projects currently under construction in the UK – Glasgow, Milton Keynes and Derby – will process residual waste.
Energos’s technology has the advantage of having reference plants in commercial operation, and is therefore well proven and has no technical risk. This has enabled it to participate in the procurement process, in partnership with a waste service provider, for waste disposal contracts being tendered by local authorities.
The Isle of Wight facility was retrofitted with the Energos technology in 2008 as part of Defra’s New Technology Demonstrator Program, and was the first thermal ACT to be accredited by Ofgem for ROCs.
The community-scale solution is based on a modular design with each ‘line’ having a processing capacity of six tonnes an hour or around 50,000 tonnes a year of waste. The current projects in the UK have either two or three lines, and generate up to 14MW of renewable electricity for export to the grid, benefitting from ROCs.
Anthony Grimshaw is technical director at Energos