Biomass[24]

In temperate regions the average annual production of dry lignous material is 10 tons per hectare, with the maxima reaching 20t/ha. This corresponds to a gross resource between 3.6 and 7.2 toe /ha, i.e. between 40 and 80 MWh. As compared to the average annual insolation of $1.5\times10^{4}$ MWh/ha this corresponds to an efficiency between 0.2 à 0.5%. Taking into account the thermodynamical efficiency for electricity production, the maximum efficiency for electricity production is 0.2%. A facility producing 7 TWh per year would require a cultivated area of about 2500 km², in the best cases. This surface could be twice less under tropical conditions.

The present world biomass energy production amounts to approximately 70 Gtoe/year. Humans use about 6% of this production either for producing food(2 Gtoe ) or for energy production (1Gtoe ). In the most bio-mass intensive scenarios given at the 1992 U.N. Rio Conference, bio-mass energy production would be as high as 5 Gtoe , and the total human use would amount to 13 Gtoe , i.e. around 20% of the available resources.

Due to its large volume bio-mass has to be transformed in high energy content material close to its production location. Aside from local uses it is foreseen to transform biomass into gas(methane), alcool(ethanol, ETBE) or vegetal oil ester. At the present time electricity production using the bio-gas is only marginally competitive when the cost of the bio-mass is negligible. Otherwise the cost of bio-gas electricity is 3 times more than that which can be obtained with fossil fuels. The cost of biofuels is about 3 times that of the fossil fuels.