Life cycle and sustainability assessments of biorefineries producing glucaric acid, sorbitol or levulinic acid annexed to a sugar mill

Abstract

Abstract To advance the ‘green’ economy agenda aimed at mitigating environmental impacts, a holistic approach assessing sugarcane biorefineries is vital in establishing their sustainability (economic, environment and social matters). This study evaluates the environmental impact of six (bio)energy self-sufficient biorefineries (S1-S6), annexed to a sugar mill and using sugarcane residues to produce sorbitol, glucaric acid and levulinic acid, along with electricity. Different pretreatment technologies, i.e. SO2-steam explosion and dilute acid, were investigated for sorbitol and glucaric acid production (S1-S4). Scenario S5 investigated levulinic acid and furfural production via the Biofine process, whereas S6 added the manufacture of gamma valerolactone to S5. Life cycle assessments evaluated using SimaPro PhD 8.5.2.0 and together with inventory data from previous Aspen Plus® v 8.6 models on economic and social impacts were used to evaluate the scenarios’ sustainability. Results revealed that dilute acid pretreatment applied in S2 and S4 exhibited 23%-92% lower environmental impacts across most impact categories, compared to S1 and S3 via SO2-steam explosion, mainly due to reduced SO2 emissions. Regarding the scenarios’ sustainability based on a combination of eight socio-economic and environmental indicators, S4 producing glucaric acid via dilute acid pretreatment was the most favourable as it had the least environmental burdens despite being marginally profitable and creating 49 jobs. It was followed by S5, the levulinic acid and furfural biorefinery whilst S6, despite attractive socio-economic outcomes was the least desirable due to high environmental loads from gamma valerolactone production, associated with the manufacture, transportation and use of n-butyl acetate solvent and hydrogen from natural gas.