Tropical Forage Biomass As An Alternative Source for Ethanol Production.

The recent increase on oil prices at the international market, associated with the imminent need to reduce the emission of greenhouse gases, has led governments in several countries, and consequently the international scientific community, to search for new biomass sources that could increase the options to produce ethanol fuel. Among the various sources of materials, currently evaluated as alternatives, the use of forage biomass is presented as one of the most viable. The use of forage biomass could considerably reduce the competition for land used for food production, providing an alternative source which is cheaper than sugarcane used for this purpose. Factors such as the large amount of biomass produced by some species, wide climatic and soil adaptation, relatively low demand for inputs; perenniality of the crops, and of course the possibility of their use for production of products such as meat and milk, make them assume an important role in this new energy scenario. Among grasses that could be used for ethanol production, in Brazil, Brachiaria brizantha, Panicum maximum and Pennisetum purpureum presented the most promising possibilities. At the Cerrados Research Center (Embrapa, Planaltina, DF), using a crop management to allow maximum biomass productivity and dry matter content (single harvest – oct/aug), biomass DMY, cellulose, hemicelluloses and lignin content were evaluated. Brachiaria brizantha presented  18 Mg/ha with 28% of cellulose, 31% of hemicelluloses and  3% of lignin. Panicum maximum produced 32 Mg/ha with 29% of cellulose, 30% of hemicelluloses and 4% of lignin. P. purpureum produced 33 Mg/ha with 28% of cellulose, 32% of hemicelluloses and 6% of lignin. Taking into account the available technology for lignocelluloses ethanol production, which considers, only the cellulose fermentation, the maximum theoretical ethanol yield for Brachiaria brizantha is  7700 L/ha, 13600 L/ha for Panicum maximum and 12375 L/ha for P. purpureum.