ENVIRONMENTAL PROTECTION Bioenergy is considered as the resource with the highest environmental impact amongst the renewable energy sources and this does not refer to incineration or waste treatment only, but it even applies to wood combustion. This is due to the fact that there are always residues (such as ash and liquid effluents) to be disposed off and practically in all applications there is a stack or a chimney. This may induce the general public to relate bioenergy plants to coal fired plants, incinerators and in general emission of gaseous pollutants. It is therefore mandatory that all Bioenergy technologies must carefully and convincingly address the problem of emissions if they are ever going to be accepted by the general public, the political establishment and subsequently the industry. Practically in all Bioenergy applications at the end the energy carrier (biogas, fuel gas, bio-oil, ethanol, solid fuel or hydrogen) will be used in a combustionprocess to release the chemical energy of the carrier. It is therefore of critical importance that emissions from the combustion of all energy carriers are minimised to whatever possible extend. It is preferable whenever possible to try to reduce the concentration of the pollutants in the energy carrier before it's combustion so as to minimise or eliminate emissions of sulphur oxides, heavy metals, halogenated compounds and other pollutants. This can (be achieved in gasification or pyrolysis processes, however, it is not possible for combustion unless extensive feedstock pretreatment takes place which is always relative expensive. In the medium term future this can prove an advantage for gasification and pyrolysis processes for contaminated biomass or waste recovered fuels in relation to combustion. Although there has been significant progress in the reduction of emissions for all the above pollutants, this is a field where the R&D work should be intensified. This is becoming even more critical as waste recovered fuels and contaminated biomass such as demolition wood are becoming an important cheap resource in countries where there is scarcity of other biomass feedstocks.