Life Cycle Assessment of Cellulose Nanocrystals Production in Sugarcane Biorefineries

The purpose of using Life Cycle Assessment (LCA) in this work was to evaluate the cellulose nanocrystals (CNCs) production in sugarcane biorefineries, identifying hotspots that can direct to process design changes to reduce environmental footprint. Modeling and simulation of an incremental unit for CNCs production from sugarcane bagasse (the main residue from the sugarcane industry) was carried out. In order to proceed the LCA, an inventory of raw-materials, products and emissions was made. The analysis employed the cradle-to-gate approach. The Global Warming Potential (GWP) metric was estimated using the SimaPro® software and using the EcoInvent v.3.3 database. LCA results showed that daily production of 7.73 ton of CNCs occurred with accumulated GWP of 23.6 tons of CO2 equivalents. Ethanol from organosolv pretreatment, sulfuric acid from hydrolysis, and sugarcane bagasse burning for steam and energy generation were the main contribution inputs for GWP. An estimated GWP of 0.23 kg of CO2 equiv. per kg of dry equiv. CNCs (or 13.43 g of CO2 equiv. / MJ of process outputs) were accounted after energetic allocation. In other impact categories aside from GWP, the environmental impacts of H2SO4 were generally the most relevant, especially in the abiotic depletion.