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Energy from Waste
Energy from waste (efw) is the thermal treatment of waste to recover renewable energy in the form of electricity and/or heat. Accounting for 9% of MSW treatment in the UK, efw plays a crucial role in meeting the targets of the Landfill Directive by maximising the amount of waste beneficially reused through recycling materials and recovering energy.
The electricity generated from the biodegradable fraction of waste accounts for nearly half of all the UK’s renewable energy generating capacity. Over 4% of the UK’s electricity was generated from renewable sources in 2005, and 31% of this was produced by waste management companies:
- 25% of the UK’s renewable energy was generated from landfill gas
- 6% of the UK’s renewable energy was generated from thermal efw plants
A further proportion was derived from the incineration of wood wastes, farm waste digestion, poultry litter combustion and meat and bone combustion.
Energy from waste facilities in the UK
There are twenty energy from waste facilities currently in operation in the UK (18 in England and two in Scotland) generating around 300 MW electricity from the combustion of almost 4 million tonnes of waste per annum (tpa). The capacity of the individual facilities ranges from 26,000 tpa at Lerwick to 530,000 tpa at Edmonton in London.
Several facilities are Combined Heat and Power (CHP) plants and supply heat-as well as electricity-to homes and businesses. CHP increases the efficiency of a power generation plant although the feasibility of CHP schemes is dependent on the availability of an end-user for the heat.
Even so, the UK recovers a relatively small amount of energy from waste in comparison with other countries.
Energy from waste and recycling
Other European countries have demonstrated that high rates of recycling can coexist with the extraction of energy from waste. For example, Denmark, the Netherlands and Switzerland all recycle over 35% of their waste at the same time as recovering energy from at least a third of their municipal waste.
Many facilities in the UK now incorporate recycling plants which sort waste to recover recyclable material before the residual waste is sent for energy recovery. Incinerator bottom ash (IBA), which constitutes approximately 25% by weight of the input waste, is a residue from the combustion of waste. Ferrous and non-ferrous metals are recovered from IBA and the remainder can be used as a substitute for natural aggregate, displacing the use of non-renewable virgin materials. Approximately 750,000 tonnes IBA are produced each year and over half is recycled as secondary aggregate for roadbase material, asphalt and concrete building blocks.
Emissions
Emissions to the atmosphere from efw facilities are closely monitored for a wide variety of potential pollutants. The Waste Incineration Directive which applies to all energy from waste facilities set stringent emission controls and resulted in significant reductions is emissions from energy from waste facilities which treat municipal solid waste. For example, between 1993 and 2003 (latest available figures ) :
- Dioxin emissions fell by 99.99%.
- Lead emissions fell by 99.50%;
- Sulphur dioxide emissions fell by 99.38%;
- Nitrous oxides fell by 81.82%; and
- Particulate emissions (PM10) fell by 99.17%;
The Government’s figures report that energy from waste facilities now contribute less than 2% of the total UK dioxin emissions. Energy from waste facilities also contribute less than 0.05% of the UK’s NOx emissions, less than 0.05% of the UK’s SO2 emissions, less than 0.01% of the UK’s particulate matter (PM10) emissions and less than 0.01% of the UK’s volatile organic carbon (VOC) emissions.
Environment and health effects
In 2004, DEFRA published a report, “Review of Environmental and Health Effects of Waste Management: Municipal Solid Waste and Similar Wastes”. Peer reviewed by the Royal Society, the report concluded that risks to human health from incineration are small in comparison with other known risks and that there was no evidence for a link between the incidence of disease and the current generation of incinerators. In addition, the role of incineration with energy recovery was acknowledged as a sustainable waste management option.
Advanced thermal treatment of MSW in the UK
In 2004 Fichtner Consulting Engineers assessed the viability of advanced thermal treatment of MSW in the UK. They analysed a range of advanced thermal technologies, identified barriers to their effective implementation, and the action required to overcome them.
The report found that few of the general perceptions about pyrolysis and gasification-for instance higher recycling rates, lower emissions and higher energy efficiencies-were based on hard evidence. 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.
June 2006
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