Energy From Waste (Thermal)
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Several thermal treatment technologies are used to extract energy from waste, including incineration and Advanced Thermal Treatment (ATT) processes such as gasification and pyrolysis. The main difference between these processes is the amount of air (oxygen) present. Pyrolysis takes place in absence of air, gasification in partial air (not enough to allow full combustion of waste) and incineration in excess air (sufficient to allow “complete” combustion of waste). Direct incineration can produce useful heat, potentially combined with power production (CHP). The gas or liquid fuels produced by ATT processes can be used in boilers or CHP engines.
Types
- Medium to large scale, eg community use, waste treatment sites. Min. 10,000 tonnes waste a year, larger for incineration.
Other components
- CHP engine or boilers to convert products to heat and/or power
- Fuel and residue storage and transportation
- Communal energy centre to house large scale plant
- District heat network
Typical saving
Scheme-dependent. Thermal treatment of waste is not carbon neutral, but by diverting waste from landfill, greenhouse gases such as methane that would otherwise be emitted to the atmosphere are controlled and used to displace demand for fossil fuels.
Indicative cost
Indicative capital costs for incineration for a typical 50,000 tonnes per annum facility are in the region of £25m. Indicative capital costs for ATT technologies for a typical 25,000tonnes per annum facility are in the region of £10m. Maintenance and operation typically 3% per annum of the total capital cost.
Main issues affecting feasibility
- Heat and power demand: Most efficient if heat can be used, so year round demand ideal.
- Consistency of waste: Consistent quality of the feedstock and sufficient pre-treatment (i.e. segregation) to ensure a “clean” organic stream are crucial for the optimum performance of the process.
- Resource use: Should only use residual waste, after reduction and recycling.
- Traffic: from waste deliveries
- Pollution and health: including odours, bio-aerosols, dust, noise, vermin
- Visual impact and public perception
