Environmental impact assessment of lignocellulosic lactic acid production: Integrated with existing sugar mills

Abstract

Lactic acid (LA) is considered for the diversification and value addition to sugar industry in South Africa, through a bioconversion of sugarcane bagasse and leaves. A bioconversion process was modeled in Aspen Plus® V8.6 and its environmental impacts were evaluated using the Life Cycle Assessment method using SimaPro® considering its integration into existing South African Sugar mills. The life cycle approach took into account the whole sugar production chain, including sugarcane cultivation stage, harvesting and transportation of sugarcane, sugar mill, and LA production. The life cycle inventories of the sugarcane cultivation and sugar mill were obtained from literature while Aspen Plus® simulation data were used for the LA production. The ecoinvent database of SimaPro® was used for all external inputs and fossil-based LA production. Environmental impacts of the biobased and fossil based LA productions were assessed and compared. The total environmental savings of the major impact categories obtained upon replacing a tonne of fossil-based LA with biobased LA are: 3925.65kg CO2 eq. of global warming potential; 1742.05kg fossil fuel eq. of abiotic depletion potential; 1296.16kg 1,4-DB eq. of human toxicity potential; 397.79kBq U235 eq. of ionizing radiation potential; 253.97kg Fe eq. of metal depletion potential; 43.48kg 1,4-DB eq. of marine aquatic ecotoxicity potential; 42.97kg 1,4-DB eq. of fresh water aquatic ecotoxicity potential and 18.23kg SO2 eq. of acidification potential. Auxiliary chemicals used in the biobased LA production are most relevant to the total environmental impacts. Thus, biobased LA production has significantly reduced the impact on the environment, giving 80–99% environmental savings compared to fossil-derived LA.