Comparison of different biodiesel production technologies in the context of a soybean biorefinery

Biorefineries play an important role in the current energy scenario, serving as platforms for energy, biofuels, and high-value-added products generation, combining energy efficiency and sustainability. One of the most well-established biorefineries is the soybean biorefinery, where the oil can be used for fuel or food production. If used for fuel production, different technologies are available for biodiesel production, because much effort has been done in the last decades to overcome the limitations of the conventional route. Although no alternative technology has proven superior enough to justify a definitive market shift, some appear more promising than others and may benefit from certain economic contexts. However, a comparison between different technologies has never been made considering the whole biorefinery framework. Therefore, in this work, we evaluate how different biodiesel production technologies respond in the context of a soybean biorefinery. Homogeneous alkaline and acid catalysis, heterogeneneous chemical and enzymatic catalysis, and the supercritical process were compared for biodiesel production with methanol and ethanol. Literature process simulation references were used to supply the information needed for the mass balances solved, and hyphotetical scenarios created for those process alternatives for which data was not available. These hyphotecical scenarios must be considered preliminary estimates and would require further validation, but served to allow a broad comparison between the different process alternatives. Homogeneous alkaline transesterification with methanol is indeed the most economic alternative (NPV of US$ 54 million in the base case scenario) and it is clear that ethylic biodiesel is more expensive (∼1.5% on average) not only because of ethanol’s higher price, but also because of the higher utility costs required for its use. Into the whole soybean processing chain, although less profitable, the heterogeneous transesterification showed to be also economically feasible (NPV of US$ 26 to 29 million), while the acid homogeneous (US$ −124 to −117 million), enzymatic (US$ −92 to −89 million), and supercritical (US$ −48 to −49 million) transesterification routes are unfeasible. However, as demonstrated, the economic performance of any route is highly sensitive to input prices and product demands, and the least profitable technologies could become interesting in the future depending on the market constraints.