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Energy from Waste
Energy from waste (efw) is the thermal treatment of municipal solid waste (MSW) under controlled conditions, recovering renewable energy in the form of electricity and/or heat. Accounting for 8% of MSW treatment in the UK, efw plays a crucial role in an integrated portfolio of waste management activities, maximising the amount of waste beneficially reused through both recycling materials – where markets exist – and the recovery of energy.
Background
Fifteen efw facilities currently operate in the UK (13 in England and two in Scotland). These plants generate 210 MW electricity from the combustion of 3 million tonnes per annum (tpa) MSW. The size of these facilities ranges from 26,000 tpa (Lerwick) to 600,000 tpa (Edmonton).
The Lerwick efw scheme generates heat only, however Nottingham, Sheffield and Coventry & Solihull have combined heat and power (CHP) facilities. CHP increases the efficiency of a power generation plant; in addition to generating electricity for the national grid, heat is provided for district heating schemes. However, the feasibility of CHP schemes is dependent on the availability of an end-user for the heat generated.
The UK recovers a relatively small amount of energy from waste:
Other European countries have demonstrated that high rates of recycling, can coexist with the extraction of energy from waste.
As part of integrated waste management, and in line with the waste hierarchy, efw plays a crucial role in increasing the UK’s recycling and recovery rates. For instance, the Edmonton efw plant is currently developing an Ecopark where recycling, composting and incineration will ensure an integrated approach to the management of North London’s waste.
IBA Recycling
Incinerator bottom ash (IBA) is a residue from the combustion of MSW, constituting approximately 25% by weight of the input waste. Ferrous and non-ferrous metals can be recovered from the ash and the remainder used as a substitute for natural aggregate.
IBA possesses similar properties to natural aggregates, and offers significant environmental and social benefits. These include reduced quarrying of virgin materials, a reduction in transport both of quarried materials to cities where IBA is available and of IBA to landfill, and preservation of landfill capacity.
Approximately 600,000 tonnes IBA are produced each year and over half is recycled as secondary aggregate for roadbase material, asphalt and concrete building blocks.
Emissions
Over recent years there have been significant reductions in emissions from efw plants. For example, between 1992 and 1998:
• Cadmium emissions fell by 98.7%;
• Mercury emissions fell by 94%;
• Lead emissions fell by 98%;
• Particulate emissions (PM10) fell by 93%;
• Sulphur dioxide emissions fell by 96%; and
• Dioxin emissions fell by 99%.
The Waste Incineration Directive, which applied to new efw facilities from 28 December 2002 and will apply to existing facilities from 28 December 2005, will see emissions controls tighten even further. DEFRA recently consulted on the Government’s Guidance on implementation of the Directive.
Emissions from efw facilities compare favourably with emissions from other sectors. For example:
• In 2000, efw plants contributed 0.8% of total regulated dioxin emissions compared with power stations (4.7%), iron and steel industry (13.1%), domestic heating (19.4%);
• In 1999, efw plants accounted for 0.2% of total UK NOX emissions, compared to road transport which accounted for 44.5% of the total; and
• Dioxin levels in processed IBA are typically less than 10 ng/kg, - comparable to typical urban soils in the UK – and lower than dust found in the streets of central London.
Advanced Thermal Treatment
The Environmental Services Training and Education Trust published ‘The viability of advanced thermal treatment of MSW in the UK’ on 31 March 2004. The report provides objective information for local authorities and others making waste management decisions. It analyses a range of advanced thermal technologies, identifies barriers to their effective implementation, and the action required to overcome them.
The report found that many of the perceived benefits of gasification and pyrolysis over combustion technology were unfounded. The report also warned that real or perceived technology risk and the rigorous requirements of private finance mean that standalone gasification and pyrolysis plants that are not commercially proven for thermal treatment of residual MSW would generally be difficult to deliver in the UK in the near future. In the short to medium term, there is potential for these technologies where:
• RO benefits make them commercially competitive with conventional technologies;
• a local authority is partial to new technologies but not combustion; and
• the waste stream is either homogenous or consists of small quantities of high value clinical and hazardous waste.
The report concludes that if Government wishes to see progress in this field, it will need to deliver a more supportive framework within which long-term development is encouraged and fostered.
May 2004
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