Environmental hazards
During the gasification of wood and/or agricultural residues, ashes (from the gasifier and from the cleaning section) and condensate (mainly water) are produced. The latter can be polluted by phenolics and tar.
The ashes do not constitute an environmental hazard and can be disposed of in the normal way. For the tar-containing condensate the situation is different, and disposal of those from a large number of gasifiers can have undesirable environmental effects. No hard data are available on the bio-degradation of the phenolic and tarry constituents of the condensates, and the problem of disposal needs careful study.
The properties of exhaust emissions from engines run on producer gas are generally considered to be acceptable, comparable to those of diesel engines.