Energy from Waste / Waste to Energy (WTE)
Where waste cannot be prevented or recycled, there are several technologies available to treat it, including those providing energy from waste. ‘Energy from Waste’ refers to two families of technologies: biological technologies, like Anaerobic Digestion (AD), and thermal technologies, like Combustion, Pyrolysis or Gasification. These technologies prevent waste going to landfill and help avoid greenhouse gas emissions, generate renewable heat and electricity and valuable residues, and help meet our international environmental obligations under the European Union’s Waste Framework Directive and Landfill Directive.
Anaerobic Digestion provides a means of dealing with organic wastes, like food and garden waste. Microorganisms break down these organic wastes in the absence of oxygen or air, producing a mixture of carbon dioxide (CO2) and methane called biogas and a solid residue called digestate.
The biogas is an energy-rich gas which can be combusted to produce heat and electricity, or can even be treated and injected into the National Grid, providing our homes and businesses with a renewable gas supply.
Combustion, Pyrolysis and Gasification provide a means of dealing with mixed residual waste - ‘black bag’ waste and other wastes that can not be recycled. These processes typically heat wastes to release their energy value, producing heat and electricity, and a solid residue called Incinerator Bottom Ash (IBA) or slag. Metals, like iron and aluminium, that had remained in the ‘residual stream’ survive the combustion process and can be extracted from the residues and recycled.