Economic and Greenhouse Gas Efficiency of Honey Mesquite Relative to Other Energy Feedstocks for Bioenergy Uses in the Southern Great Plains

Abstract

The US Environmental Protection Agency (EPA) implemented the revised Renewable Fuel Standard (RFS2) in 2010, which mandates that a minimum of 16 billion gallons of cellulosic biofuel be produced by 2022. Woody plants growing on native rangelands in the Southern Great Plains (SGP) region of the USA, such as honey mesquite and juniper species, may have potential as bioenergy feedstock, but there are concerns regarding variability in biomass density distribution and high harvest and transport costs. The objective of this study was to evaluate economic and greenhouse gas (GHG) performances of honey mesquite relative to irrigated and dryland sweet sorghum and dryland switchgrass bioenergy feedstock as delivered to the farm gate. Four efficiency criteria such as biomass production cost, energy cost, GHG offset, and GHG use were calculated. Our results suggest that mesquite lagged slightly behind switchgrass when biomass and energy efficiency are considered. However, mesquite appears superior to the other feedstocks in two categories—GHG offset efficiency and GHG use efficiency once land use change (LUC) effects are accounted for. Mesquite as a bioenergy feedstock in the SGP has greater potential if additional benefits such as increased grass production for livestock production and reduction in herbicide costs for mesquite control—both of which would occur as a result of mesquite harvesting—are considered. Mesquite production values on a per-land area basis are lower than the other feedstocks observed in this comparison and therefore could not supplant those feedstocks entirely, but mesquite appears to be suitable as a complementary feedstock to contribute to total biomass feedstock demand.