Reconciling the sustainable manufacturing of commodity chemicals with feasible technoeconomic outcomes: Assessing the investment case for heat integrated aerobic gas fermentation

The manufacturing industry must diverge from a ‘take, make and waste’ linear production paradigm towards more circular economies. Truly sustainable, circular economies are intrinsically tied to renewable resource flows, where vast quantities need to be available at a central point of consumption. Abundant, renewable carbon feedstocks are often structurally complex and recalcitrant, requiring costly pre-treatment to harness their potential fully. As such, the heat integration of supercritical water gasification and aerobic gas fermentation, unlocks the promise of renewable feedstocks such as lignin. This study models the techno-economics and life cycle assessment for the sustainable production of the commodity chemicals, isopropanol and acetone, from gasified Kraft black liquor. The investment case is underpinned by rigorous process modelling informed by published continuous gas fermentation experimental data. Time series analyses support the price forecasts for the solvent products. Furthermore, a Monte Carlo simulation frames an uncertain boundary for the techno-economic model. The techno-economic analysis demonstrates that production of commodity chemicals priced at ~$1000 per ton is within reach of aerobic gas fermentation. In addition, owed to the sequestration of biogenic carbon into the solvent products, negative greenhouse gas emissions are achieved within a cradle-to-gate life cycle assessment framework. As such, the heat integrated aerobic gas fermentation platform has promise as a best-in-class technology for the production of a broad spectrum of renewable commodity chemicals.