Simulation and LCA of a bioethanol process technology in development

Paper in proceeding, 2013

The development of sustainable processes for the production of second generation biofuels is an ongoing effort. Not only does such a process need to be economically feasible, it should also produce a biofuel that has a lower environmental impact compared to first generation biofuels or fossil fuels. In this work, Life cycle assessment (LCA) is used for the evaluation of such a process along its development path. The objectives of this evaluation are to help improve and/or optimize the process in development from an environmental perspective and to help guide this development. In particular, the process under study uses high-gravity fermentation, i.e. a process with a high solids concentration in the fermentation reactor, for the production of ethanol from wood and straw. A simulation model of a plant with an industrially relevant capacity using the high-gravity technology has been set up in order to address issues of scaling up the process in development (process-level scale). Data from lab experiments are used by this model and the simulation results are subsequently used in the LCA model in order to calculate the environmental impact of the technology at an industrial scale. Furthermore, the scale at which biofuels are applied in land transport, partly due to targets set in e.g. the EU Renewable Energy Directive, needs to be accounted for (biofuel sector-level scale). The consequent feedstock use, and resulting land use and land use change impacts, as well as biogenic carbon emissions need to be included in the LCA. This paper discusses the modeling at the aforementioned process level and results are presented in order to demonstrate the importance of considering scale issues at this level. The inclusion of scale issues at the biofuel sector level in LCA will be discussed.