Profitability of single- and mixed-culture fermentations for the butyric acid production from a lignocellulosic substrate

Abstract

Butyric acid (BA) is one of the most promising precursors for pharmaceutical and plastic manufacturers, as well as for fuel butanol production. Lignocellulosic biomass can be used as an adequate source for BA production due to its low prices and widespread abundance. The conversion of lignocellulosic biomass into BA requires different steps depending on the type of inoculum. Pure cultures, which produce high amounts of BA, demand sequential processing of lignocellulosic substrates. In contrast, mixed cultures, which produce a lower amount of BA, work as a consolidated bioprocess, therefore, some processing steps occur simultaneously. It is unknown which of these two schemes for BA production is more profitable yet. The following study presents a review about the most recent advances about BA production from lignocellulose by pure and mixed cultures. In addition, a techno-economic analysis for BA production is considered for each type of inoculum and different plant capacities. The pure strain scheme involves seven stages, while the mixed culture scheme involves only four. Both schemes include the final product purification through membranes where the purity of BA was 99.8%. The mixed culture scheme is more profitable than the pure strain one, with Total Production Costs of 3.2, 1.3, and 0.9 US$/kg for plant capacities of 100, 500, and 1000 ton/day, respectively. With respect to the pure strain scheme, the Total Production Costs are 15.1, 7.3, and 6.5 US$/kg for plant capacities of 100, 500, and 1000 ton/day, respectively. The operating costs in the pure culture plants are 30.4, 81.7, and 145.2 million US$/year for the plant capacities of 100, 500, and 1000 ton/day, respectively. These operating costs are between 1.2 and 1.5 times higher compared with the mixed culture plants. Also, the Total Capital Investment is three times higher with the pure strain scheme.