In a communiqué, the six organisations point out that electricity obtained from burning trees will never be green, and say that the European policy of using forest biomass to produce electricity is socially contested and opposed by many scientists.

The communiqué talks about the loss of tree cover resulting from the production of electricity, inside and outside the European Union, and says that it is claimed that forest waste is being used to burn in thermoelectric power stations or to make 'pellets', but in fact tree trunks are being used "almost exclusively".

"In any case, the so-called "waste" is in fact surplus material from forestry activities, essential to maintain soil fertility, especially in Portugal, a country where the majority of soils are very poor in organic matter content", the organisations warn.

In the statement, environmental organisations Zero, Quercus, Iris, Fapas and Geota, and Acréscimo, Association for the Promotion of Forest Investment, also stress that woodlands in Portugal are victims of over-exploitation, that fires have increased the scarcity of raw material, and that the growing number of licensed units for biomass burning or production of 'pellets' has further increased the pressure on forests.

"The impacts on ecosystems, biodiversity, soils and water resources have been very harmful. In addition to the impacts on ecosystems, there are the risks of significant atmospheric and noise pollution inherent in the operation of tree-burning plants", say the organisations, stressing that burning trees to produce electricity does not produce fewer emissions or generate less pollution than fossil fuels.

The six associations doubt that opting for bioenergy will have an impact on the problem of forest fires and also say that investment in biomass is not rational and that it is only viable with strong public support and a "considerable financial effort" from electricity consumers.

The appeal comes in the wake of a new European Union directive on renewable energy due to be presented in July.

Recently other environmental organisations from several European Union countries had already considered biomass to produce electricity as unsustainable and inefficient