Energy and economical comparison of possible cultures for a total-integrated on-field biodiesel production

Abstract

This work is aimed at investigating the energy conversion effectiveness and the economical advantages of a total integrated solution for on-field biodiesel and electrical energy production. The system proposed here is based on the synergy of four sub-systems: a seed press for oil production, a downdraft gasifier, a biodiesel conversion plant and a Solid Oxide Fuel Cell (SOFC). Two possible culture rotations, suggested by literature review, were analyzed here from economical and energy balance points of view. Both the rotations were composed of oleaginous crops only, therefore the seeds collected from the different cultures were pressed, then the protein cake produced in the process was gasified in the downdraft reactor. The gasification process was modeled here, and its output suggested that, for a precise number of hectares, the syngas obtained through the cake gasification was enough for producing methanol required for oil-biodiesel conversion and feeding a 10-kW SOFC. The purge line in the methanol reactor was used in the SOFC as well. The system was simulated using ASPEN PLUSTM and MATLABTM codes. Results of the SOFC and gasifier models underlined the capability of the fuel cell to work with this particular system, furthermore the whole system analysis suggested that the surface required for sustainability of the processes is a function of the rotation choice. In both cases little surfaces ranging from 11 to 21 hectares were found to be enough for system self-sustainability with a ROI under 7 years in all the operating conditions analyzed.