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ENERGY FROM WASTE
Energy from waste (efw) is the recovery renewable energy in the form of electricity and/or heat from residual waste. Accounting for 9% of municipal solid waste (MSW) treatment in the UK, recovering the energy from waste plays a crucial role by maximising the amount of waste beneficially reused through recycling materials and the recovery of energy. Recovering energy from waste displaces emissions that would otherwise be emitted by fossil fuel power stations and helps increase the UK’s own security of fuel supply.
Energy from waste facilities in the UK
Twenty energy from waste facilities currently operate 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 schemes can increase the efficiency of a power generation plant although the viability of a CHP scheme is dependent on the availability of an end-user for the heat.
Generation of renewable electricity
The electricity generated from the biogenic fraction of waste accounts for a third of all the UK’s renewable energy generating capacity. According to official figures from the DTI, of the 4.2% of electricity from renewable sources utilised in the UK in 2005, 31% was derived from waste management companies:
-25% was generated from landfill gas (4,290 GigaWatt hours)
-6% from incinerating the biodegradable fraction of MSW (964 GigaWatt hours)
Renewable energy was also generated from the incineration of wood wastes, farm waste digestion, poultry litter combustion and meat and bone combustion.
Recovery and recycling of materials
Many facilities in the UK now incorporate recycling plants which recover recyclable materials and send residual waste for energy recovery. Ferrous and non-ferrous metals are further recovered from the ash following energy recovery.
Incinerator bottom ash (IBA), which constitutes approximately 25% by weight of the input waste, is used as a substitute for natural aggregate. Recycling IBA displaces the use of non-renewable virgin materials. Approximately 750,000 tonnes of IBA is produced each year and over half is recycled as secondary aggregate for roadbase material, asphalt and concrete building blocks.
Energy from waste and recycling
The UK recovers a relatively small amount of energy from waste in comparison with other EU countries which combine high recycling rates with energy recovery o. 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.
Emissions
Emissions to the atmosphere from efw facilities are closely monitored by the Environment Agency. The Waste Incineration Directive which applies to all energy from waste facilities set stringent emission controls and resulted in significant reductions in emissions from energy from waste facilities which treat MSW. For example, between 1993 and 2003 (NAEI 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 0.5% of the total UK dioxin emissions. Emissions are significantly less than the amount of dioxins released into the atmosphere on bonfire night or from accidental fires. The combined emissions of nitrous oxides (NOx), sulphur dioxide (SO2), particulate matter (PM10) and volatile organic carbon (VOC) from the all of the UK’s energy from waste facilities are significantly lower that that emitted by transport and other major industries.
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. The report, which analysed a range of advanced thermal technologies, 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.
September 2006
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