Ethanol production from tropical forage grasses

Abstract

Several tropical forage grasses - two cultivars and three hybrids of guineagrass (Panicum maximum Jacq.), two cultivars of elephant grass (Pennisetum purpureum Schum.) and one cultivar of forage sorghum (Sorghum vulgare L.), have been evaluated as to their ethanol production potentials, during two growing seasons. These estimates have been based on dry matter yields and fermentable reducing sugar contents of each germplasm tested. In the first growing season (1982/83), during which just one harvest was carried out late in the season, the elephant grass significantly outyielded (7,825 liters/ha/year - average of two cultivars) the guineagrass (3,947 liters/ha/year - average of two cultivars) and the forage sorghum (2,890 liters/ha/year). However, in the second growing season (1983/84), during which five clippings were done with a frequency of 45 days and at a clipping height of 10 cm, the guineagrass cultivars showed statistically higher ethanol yields (5,148 liters/ha/ year) than those of elephant grass germplasms (3,665 liters/ha/year). The reason for the elephant grass superiority, in ethanol production, over the other tropical forage grasses during the first growing season, appears to be its outstanding culm production, plant part that is rich in cellulose, the raw material for alcohol production in the case. The results confirmed the feasibility of using tropical forage grass species as raw materials in large scale ethanol production schemes.