What’s it all about?
This is the general term for generating power from burning or heating waste. This includes things like waste food, wood, paper, card, Animal-by-products, plastics and mixed general household waste etc. Energy from waste takes many forms and can be confusing; terms like biomass to energy, pyrolysis, gasification and fluidised bed are specific technologies associated with waste to energy.
Typically there are two groups of processes:
- Incineration - Waste is separated and shredded, metals will be removed for recycling before or after the combustion process. The remainder is combusted (incinerated), this produces heat which is used to make steam and produce electricity via a turbine. Any gases from the combustion process are then cleaned to comply with the Waste Incineration Directive (WID) before release. Electricity can be sold to the National grid and the heat can be used in district heating schemes. Two types of ash are produced by the process, fly ash and bottom ash. Bottom ash can be used as a replacement for aggregates if a market can be secured, however fly ash currently needs to be land filled in a specialist hazardous waste landfill site.
- Advanced Thermal Technologies - Pyrolysis, gasification and plasma technologies are thermal processes that use high temperatures to break down (thermally degrade) waste. The difference is the level of oxygen present. By restricting the amount of oxygen you get a heating process instead of combustion which produces a gas (synthetic gas or syngas). This is typically 85% hydrogen and can be burnt to heat water and produce steam to make electricity. Syngas can also be used as a feedstock in the petrochemical and refining industries or undergo treatment to produce hydrogen for use in fuel cells. These technologies are still classified as incineration under the European Union’s Waste Incineration Directive.
The Good Stuff
- Produces power and other useful by-products from waste.
- Diverting biodegradable waste (food, paper, wood etc.) away from landfill reduces greenhouse gas emissions.
- It’s cleaner, capturing emissions which are strictly controlled and monitored.
- Replacing fossil fuels with biodegradable waste is a low carbon method of generating renewable electricity.
- Specialist facilities can process difficult waste streams such as animal by products safely and efficiently, destroying toxins and pathogens.
- Reduces waste volume significantly.
Not so Good
- Perception – It is important to promote understanding of the process and any emissions. For a long time, EFW often referred to as just “Waste Incineration” has been subject to strong opposition. Modern EFW plants comply with very strict emissions controls and this technology has become more widely accepted as a process for waste reduction but residents and local businesses of proposed plants often raise concerns.
- Whilst the production of biomass (i.e. growing crops to burn and produce energy) may have a poor reputation with concerns around the replacement of food crops this is separate issue to using waste or by products for energy generation.
- Can be a more expensive option but this is expected to change.
- It can be seen as discouraging recycling although this has not been the case in practice where other European countries have promoted EFW.
- Emissions to air need to be managed correctly.
- Residual ash requiring specialist disposal.
- There are still older style operations which are not truly waste to energy but these are being replaced.
Top Tips
- Check the environmental credentials of the destination e.g. correct permits, by products etc
- Check the process to ensure material is segregated and recycled prior to incineration
- Check using this disposal route will not conflict with your CSR or company policies
Source: http://www.igd.com/index.asp?id=1&fid=5&sid=43&tid=158&foid=127&cid=1702
