Environmental sustainability evaluation of glycerol and propylene-based pathways to acrylic acid via different intermediates

Acrylic acid is an important industrial chemical used for the manufacturing of many consumer products. It is currently produced using fossil fuel-based propylene via acrolein intermediate. However, it can be sustainably produced from glycerol, the major by-product of biodiesel industry, through different pathways that involves intermediates such as acrolein, allyl alcohol, or lactic acid. This study investigates the cradle-to-gate life cycle assessment of four acrylic acid production routes, utilizing Aspen plus software and CCaLC2 tool following ISO 14044:2006. Environmental impacts, including global warming potential, water footprint, acidification, eutrophication, ozone layer depletion, photochemical smog, and human toxicity, are evaluated. Glycerol-based processes exhibit significant environmental impacts mainly due to energy-intensive production of epichlorohydrin-derived glycerol. The total global warming for glycerol-based processes having intermediates allyl-alcohol, lactic acid and acrolein were 167393.76, 179631.05 and 133981.22 kg CO2 eq. FU-1 respectively with epichlorohydrin-derived glycerol and this value was 55181.66 kg CO2 eq. FU-1 for propylene-based process. However, after changing the source of glycerol by purified crude glycerol from the biodiesel industry results in considerable reduction of the environmental impact. Moreover, it is reported that crude glycerol derived from the biodiesel industry can be purified by different purification methods and depending on the glycerol content in crude glycerol, changes in carbon emissions are observed. Hence, a sensitivity analysis using the two-factor interaction (2FI) model on various purification processes and glycerol content was carried out. It showed that a vacuum distillation purification process with 50% glycerol content reduces global warming significantly. In summary, this life cycle assessment provides insights into environmental performance trade-offs, guiding efforts towards more sustainable acrylic acid production. It highlights the importance of raw material choices and process optimization in mitigating environmental impacts and emphasizes the potential of using by-products from other industries to enhance sustainability in chemical production processes.