Pyrolysis is a thermal process where organic materials in waste are broken down under pressure and in the absence of oxygen. Best results have been obtained from single stream wastes such as sewage sludge, plastics, wood, tyres, or agricultural wastes. Pyrolysis has not been widely applied to municipal waste, but has been applied to some higher value wastes on a commercial scale.
Dependent upon the details of the process design, the pyrolysis process produces a liquid and / or solid residue and gaseous output. Each of these products may be combusted to recover energy from the waste. If there are suitable markets, some products have the potential to be supplied for use – this may restrict the waste that is received for treatment. Unused products may have potential for other recovery and use, or require disposal.
Pyrolysis plants use a process similar to that used for the manufacture of charcoal.
How it works
Pyrolysis is most often used in combination with gasification and a combustion stage to recover energy. Some pilot and commercial scale plants have been constructed. Application of the technology to mixed wastes such as MSW has so far proved challenging.