Effect of production scale on the techno-economic viability and environmental life cycle analysis of lactic acid production in a sugarcane biorefinery

Abstract

Biorefineries are vital for advancing circular economy and reducing the effects of products fossil fuels derived products on the environment. However, biorefineries often operate at smaller production scales than fossil refineries due to limited feedstock availability, which may be addressed by centralised processing with multiple feedstock sources. Lactic acid (LA) has several industrial applications and is a platform chemical used to produce products like acrylic acid and propylene glycol. The economic and environmental performances of an integrated biorefinery at different production scales, through different levels of feedstock centralization, were investigated, to determine the optimal scale for sugarcane-based LA production. Decreasing values for the minimum selling price (MSP; 1312–849 US$.t⁻¹) and increasing internal rates of return (IRRs; 31–64 %) were observed with increasing conversion scales of sugarcane A-molasses. The MSPs decrease from 90 to 450 kt_LA.y⁻¹ with small improvements in profitability beyond 450 kt_LA.y⁻¹, as confirmed by stochastic financial uncertainty analysis. In the environmental assessment, a linear increase was observed across all impact categories, mainly due to the added fuel consumption for feedstock transportation. LA production had a GWP100 range of 0.87–0.95 kg CO₂-eq.kg_LA⁻¹ and an abiotic depletion potential of 12–13 MJ.kg_LA⁻¹ which increased as the scale increased. In the ozone depletion category emissions of 9.96×10⁻⁸-1.13×10⁻⁷ kg CFC-11 eq.kg_LA⁻¹ comparable to other studies available in literature. Similarly, emission ranges of 1.11–1.17, 0.63–0.66, and 1581–1641 kg 1,4-DB eq.kg_LA⁻¹ were obtained in the human toxicity, freshwater and marine aquatic ecotoxicity categories as the scale increased. Environmentally the smallest scale at which transportation of feedstock was avoided (i.e. 90 kt_LA.y⁻¹) is preferred as opposed to 450 kt_LA.y⁻¹ for economic performance.