|
Emissions and Residues from Energy from Waste (EfW) Plants
Burning waste produces certain residues and emissions which are managed at the EfW plant using the latest technology. All plant emissions are tightly controlled by the Environment Agency and SEPA, and most have been reduced dramatically since 1990. Between 1990 and 1997 dioxin emissions from municipal waste incinerators fell by over 98 per cent and emissions of several heavy metals are now close to zero.
This was strengthened further by the European Union Waste Incineration Directive (often termed ‘WID’) 2000/76/EC which was transposed into UK law on 28 December 2002. All new incinerators have to comply with the tighter provisions of this Directive, and all previous existing incinerators have been at this standard since the target date of 28 December 2005. As well as stricter emissions limits, this Directive also requires better management systems and increased monitoring of emissions.
Emissions
Emissions to the atmosphere from EfW facilities are closely monitored for a wide variety of potential pollutants, including hydrochloric acid, nitrous oxides, sulphur oxides, dust, oxygen, total hydrocarbons, carbon monoxide, PCB's, dioxins and heavy metals. Operators of EfW plants are required to install continuous emission monitoring (CEM) for specified key emissions including particulates. The CEM equipment undergoes daily internal calibration checks and a mandatory independent quality assurance check in accordance with the relevant British Standard. Operators provide the Environment Agency with records of each measured daily average for particulates. The equipment records emissions of all particles (PM10) below 10 micrometres, which include those below 2.5 micrometres (PM25) as a sub-set.
Emissions from EfW facilities are often significantly lower than emissions from other sectors. For example:
|
Dioxins |
In 1999, EfW plants contributed 0.8% of total regulated dioxin emissions compared with power stations (4.7%), i ron and steel industry (13.1%), domestic heating (19.4%). |
|
Dioxins |
Dioxin levels in processed IBA are typically < 10 ng/kg - comparable to typical urban soils in the UK - and lower than dust found in the streets of central London. |
|
NOx |
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. |
|
CO2 |
Incineration of the biogenic fraction of municipal waste is a carbon neutral process, while CO2 emissions from the non-biogenic fraction are significantly lower than those from coal fired power stations, per kwh. |
Emissions to the atmosphere from EfW facilities are closely monitored by the Environment Agency and SEPA. The Waste Incineration Directive, which applies to all energy from waste facilities, sets stringent emission controls and when introduced resulted in significant reductions in emissions from EfW facilities treating municipal solid waste (MSW).
Defra has stated that there is “no credible evidence to suggest that modern incinerators—which must comply with stringent EU emission limits—cause health effects, beyond those which could be attributed to similarly sized ‘conventional’ combustion plant.” According to the UK Health Protection Agency, the incineration of MSW accounts for less than 1% of UK emissions of dioxins, and 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 EfW facilities are significantly lower than that emitted by transport and other major industries.
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”. This view is also reflected in a statement by the Health Protection Agency. Links to these documents can be found at the foot of this page.
Residues
The main residues from incineration plants are incinerator bottom ash and air pollution control residues, approximately 25% and 3% by weight, respectively, of the incoming waste stream.
Incinerator bottom ash (IBA) from modern EfW plants is an inert waste discharged from the end of the grate. The ash is cooled and is widely used throughout Europe as a secondary aggregate in road construction and the building industry. A report by the Environment Agency (July 2002) concluded that IBA is a valuable secondary aggregate and can be safely used in construction.
Air pollution control (APC) residues are generated when flue gases from the boiler pass through sophisticated multi-stage scrubbing systems for acid gas removal and a high efficiency filtration system. These residues are hazardous and must be safely disposed of in licensed engineered landfill site under very strict regulatory conditions.
Useful Links
Review of Environmental and Health Effects of Waste Management: Municipal Solid Waste and Similar Wastes (report by Enviros Consulting Ltd and University of Birmingham for Defra)
Health Protection Agency: Position Statement on Municipal Solid Waste Incineration
Environment Agency Position Statement on waste incineration in waste management strategies
DEFRA Parliamentary Answer 3 April 2008
|
