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What is energy from waste (EFW)?

What is energy from waste?

Energy from waste (EFW) is a type of incineration that involves burning waste at temperatures over 850°C. The waste is mixed and sometimes shredded to make sure that it will burn properly. It is then moved to a combustion chamber where oxygen is added. Incinerators use the heat from the chamber to create steam, which can then be used to make electricity by turning a steam turbine.

The steam can also be used to provide heat to local homes and businesses. These types of incinerators are called energy from waste (EFW) facilities which can operate as combined heat and power (CHP) plants if they produce heat as well.

By burning the waste, most of it turns into carbon dioxide and water. Any material that won't burn, like glass, metals or stones, collects at the bottom of the chamber and is known as bottom ash. Incinerators also create other types of gases (dioxins) and particles (fly ash). The emissions from incinerators are carefully controlled. The air is cleaned by a sophisticated air-pollution control (APC) system before it is realised in the atmosphere.

Read DEFRA's booklet Incineration of Municipal Solid Waste to find out more about incineration.

Is energy from waste better for the environment than landfill?

Well managed energy from waste facilities are clean and safe, with have a track record of reliability and efficiency. There are over 300 facilities operating in Europe and they are fundamental part of environmentally sustainable waste management.

The EU's Waste Incineration Directive (WID) (soon to become the Industrial Emissions Directive) sets out strict legislation controlling the development and operation of energy from waste facilities. Before any facility can operate in the UK it must have an environmental permit from the Environment Agency who will assess and monitor the facility based on the WID legislation.

Not only to they mean we no longer need to bury our waste in a hole in the ground, energy from waste facilities generate electricity and heat. The electricity can be used locally or fed into the national network. By burning waste to create this sort of power, rather than coal or oil, we are helping to save the earth's precious stores of these finite resources. Energy from waste can also increase recycling as the bottom ash can be processed into building materials and metals can be extracted.

Controlling emissions

Any form of combustion, be it petrol in your car or your garden bonfire, causes chemical reactions within the materials being burnt. These generate compounds, such as dioxins and particles, which if released into the atmosphere can be harmful to human health and the environment if they are not properly controlled.

Almost half of any energy from waste facility building will be taken up by the air pollution control (APC) system. This works in two ways. Firstly it helps to reduce the levels of the dioxins and particles that are created in the first place by controlling the gases within the facility's furnace. Then it catches, filters and cleans the gases through a sophisticated flue gas treatment process.

What remains are tiny quantities of compounds that are well within the limits set by the WID and the Environment Agency and do not impact on health or the environment when released into the atmosphere. In fact, in some circumstances, the level of compounds in the air around energy from waste facilities are less than in the surrounding area, meaning that the APC systems are improving local air quality.

The compounds that are trapped by the APC system create a residue that is classed as hazardous waste due to the high alkaline content of lime that is used as part of the cleaning process. The APC residues must be disposed of in a suitably licensed hazardous waste treatment facility, usually a hazardous landfill site.

The Environment Agency

The Environment Agency is responsible for checking that all energy from waste facilities in the UK meet the emissions limits set by the WID and monitoring the emissions whilst they are operational.

Health Protection Agency

The Health Protection Agency (HPA) is an advisory organisation that provides guidance to the government and the Environment Agency on the impact of energy from waste facilities. It states that: "Modern, well managed incinerators make only a small contribution to local concentrations of air pollutants. It is possible that such small additions could have an impact on health but such effects, if they exist, are likely to be very small and not detectable."

Professor Roy Harrison

As well as considering the HPA's position, the county council has also been working with one of the world's leading experts on the impact of waste management on human health and the environment.

Professor Roy Harrison is Professor of Environmental Health at University of Birmingham and is currently Deputy Chairman of the DEFRA Expert Panel on Air Quality Standards and a member of the Department of Health Committee on the Medical Effects of Air Pollutants. He was appointed an OBE for services to environmental science in the New Year Honours List in 2004.

His role involves advising county council officers and cabinet members on health and environmental impacts of waste disposal technologies.

Commenting on his appointment in 2010, Professor Harrison said: "Waste management raises many health-related questions in the minds of the public, and I look forward to working with Gloucestershire County Council to keep them abreast of the latest knowledge of this topic."