Techno-economic analysis of hydrocarbon biofuels from poplar biomass

Abstract

Infrastructure compatible hydrocarbon biofuel that is proposed to qualify as renewable transportation fuel under the U.S. Energy Independence and Security Act of 2007 (EISA) and Renewable Fuel Standard (RFS2) is evaluated. The process uses hybrid poplar for feedstock, which undergoes dilute acid pretreatment and enzymatic hydrolysis. Sugars are fermented to acetic acid, which undergoes conversion to ethyl acetate, ethanol, ethylene, and finally a saturated hydrocarbon end product with yields of 330 liters of jet fuel per bone dry tonne feed. A lignin rich stream that is not fermented may either be burned for steam and electricity production, or gasified. During the biofuel production process, hydrogen gas is required in two unit operations and may be obtained by various methods including lignin gasification. Both technical and economic aspects of the biorefinery are analyzed, with a range of hydrogen sources considered. These include steam reforming of natural gas, gasification of lignin, and electrolysis of water using seasonal excess hydroelectric capacity in the U.S. Pacific Northwest. Cash operating costs are estimated to range from 0.67 to 0.89 USD per liter of jet fuel depending on facility capacity. Capacities of 95 to 570 million liters (25 to 150 million gallons) of polymer jet fuel per year are investigated, with capital investments in the range of 304 to 1,150 million USD. The production of alternative, intermediate products to jet fuel is briefly explored.