Techno-economic assessment of a biorefinery based on low-impact energy crops: A step towards commercial production of biodiesel, biogas, and heat

Abstract

Given that castor and Eruca sativa plants are non-edible, low-impact energy crops, different scenarios for commercial-scale biorefineries based on these plants were developed. The processes were simulated by Aspen Plus™ software, and the estimation of equipment cost and economic analyses were performed by Aspen Process Economic Analyzer (PEA) software. In each scenario, biodiesel was produced by transesterification of oil extracted from castor (scenarios 1 and 3) and Eruca sativa (scenarios 2 and 4) grains, and the lignocellulosic residuals were used for biogas or heat (scenarios 3 and 4) production. Based on the simulation results, 7400–7470 m3 per year biodiesel can be produced in these processes. The production price of biodiesel was obtained as 0.28, 0.04, 0.31, and 0.02 $/L for scenarios 1 to 4, respectively. Furthermore, the total capital investment was $87, 33, 89, and 34 for scenarios 1 to 4, respectively. The energy efficiencies of these processes were 63%, 71%, 63%, and 81%, respectively. Direct heat production from residues resulted in profitable processes, while biogas production was profitable only at a capacity higher than 240,000 tonnes per year. High investment requirements and interest rate were the most important factors affecting the profitability of biogas production scenarios. The results of this study could lead the research in the area toward commercialization of profitable biorefineries.