ARCHIVE: Energy from waste and anaerobic digestion
- Government wants to maximise energy recovered from unavoidable residual waste (that would otherwise go to landfill) so as to make the greatest contribution to energy policy.
- Government wants to promote greater energy recovery from food waste (via anaerobic digestion) and waste wood (via combustion) to capitalise on the potentially significant energy and carbon benefits.
What is the Renewables Obligation?
The Renewables Obligation (RO) is the Government's main market support mechanism for renewable electricity. Electricity suppliers are obliged to source a growing proportion of the electricity they supply from renewable sources (currently up to 15.4% by 2015), confirmed by Renewables Obligation Certificates (ROCs).
What are the Renewables Obligation (RO) proposals?
The Renewables Obligation provides support for electricity produced from the biomass content of waste treated in gasification, pyrolysis, anaerobic digestion and good quality combined heat and power plants. The Government’s Energy White Paper set out:
- the energy policy benefits of recovering energy from residual waste, which contributes to security of energy supply, with the biomass element of waste also being a renewable energy source;
- plans to band the RO to provide more targeted levels of support to different renewables including eligible energy from waste schemes.
What proportion of waste do you expect to go for energy recovery?
We have not set a specific target. However there is a target for municipal waste recovery which includes recycling, composting and energy recovery. We have also set targets for the recycling and composting of household waste. While we would like to exceed both of these targets if possible, meeting them precisely would mean an increase in energy recovery to about 25% of municipal waste in 2020 compared to around 10% today.
Won’t an increase in energy from waste hinder recycling?
Recovering energy from waste which cannot sensibly be recycled remains a sound environmental objective. Many other European countries have shown that a vigorous energy from waste policy is compatible with high recycling rates. Defra research shows that recovering energy from residual waste (including by incineration) is a much better option than landfill.
What technologies should be used?
Energy from waste technologies include anaerobic digestion; direct combustion (incineration); use of secondary recovered fuel (an output from mechanical and biological treatment processes); pyrolysis; gasification and plasma arc heating. Government does not generally have a preference for one technology over another, with the exception of anaerobic digestion for treating food waste. Any given technology is more beneficial if both heat and electricity can be recovered. Choice of technology needs to reflect local circumstances, which will vary, but Government expects greenhouse gas emissions to be a key consideration of those developing waste to energy plants.
We wish to encourage more consideration of anaerobic digestion both by local authorities and businesses. Recent research shows that anaerobic digestion has significant carbon and energy benefits over other options for managing food waste (and may be particularly cost effective for food waste if separately collected).
What is anaerobic digestion?
Anaerobic digestion is a commonly used technology in some other European countries, but this is not yet the case in England. It is the biological treatment of biodegradable organic waste in the absence of oxygen, utilising microbial activity to break down the waste in a controlled environment. It results in the generation of:
- Biogas, which is rich in methane and can be used to generate heat and/or electricity;
- Digestate (or fibre) which is nutrient rich and can potentially be used as a soil conditioner; and
- Liquor, which can potentially be used as a liquid fertiliser.
What about the health impacts from waste combustion?
The recovery of energy from waste has been held back partly by public fears over alleged health effects. Concern over health effects is most frequently cited in connection with incinerators.
Research carried out to date shows no credible evidence of adverse health outcomes for those living near incinerators. Municipal waste incineration emissions have fallen considerably in recent years, with stringent emissions standards now applied through the Waste Incineration Directive. For example, according to the Health Protection Agency, the incineration of municipal solid waste accounts for less than 1% of UK emissions of dioxins. The UK experience of significant falls in pollutants has also been seen in other European countries such as Germany, which apply the same standards.
Page last modified:
18 June 2007
Page published: 24 May 2007