Estimating a net energy value for biofuel from agricultural biomass produced in Hawaiʻi

Abstract

Hawaiʻi is nearly 92% dependent on fossil fuels for energy. In order to alter this situation, there are a variety of renewable energy options available, one such option is biomass production for conversion to biofuels within the State. This research uses a format of energy analysis used for corn production on the US mainland. A Net Energy Value (NEV) calculation is derived for local biomass production and conversion of banagrass (Pennisetum purpureum Schumach). After assessing all energy associated with agricultural production of banagrass, including land preparation, labor, embodied energy of machinery and chemicals, transport of inputs and transport of biomass, various conversion efficiencies are also analyzed. For a 500-acre farm, using non-irrigated, nonprime agricultural land, the energy used for production is about 18,300,000 Btu/acre/year. The banagrass yield produces ethanol with a total energy of about 109,000,000 Btu/acre/year. The energy input of the conversion processes range from 30,000,000 Btu/acre/year to 137,000,000 Btu/acre/year, depending on the efficiency of the conversion assessment, the utilization of co-products for energy production, and accounting for embodied energy of the materials used in the plant itself. Total Net Energy Value ranges from-46,000,000 to 60,000,000 Btu/acre/year.