Independent report

Pyrolysis liquid fuels: testing emissions

Study of data to determine whether thermal decomposition of biomass materials in the absence of oxygen would affect air quality.

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Defra commissioned a scoping study of existing information to help determine whether any future use of pyrolysis oil as a fuel would have implications for air quality.

The main finding is that, based on sparse data, emissions will be dependent on the nature and coherence over time of feedstock used in individual cases.

Pyrolysis is thermal decomposition of material (biomass in this instance) in the absence of oxygen.

Pyrolysis occurs in combustion and gasification processes where it is followed by oxidation of the pyrolysis products. Lower process temperature and longer vapour residence times favour the production of charcoal. High temperature and longer residence time increase the conversion to gas. Moderate temperature and short vapour residence time are optimum for producing pyrolysis oils.