Environmental and technical feasibility of cellulose nanocrystal manufacturing from sugarcane bagasse

Abstract

The environmental and technical feasibility of cellulose nanocrystal production from sugarcane bagasse fibers was evaluated. First, the life cycle assessment (LCA) is presented as a methodology to investigate the most feasible form of obtainment. The environmental impacts regarding climate change and water footprint were evaluated considering a gate-to-gate process and a functional unit of 1kg. The inventory data encompassed sugarcane plantation and pretreatment, bleaching and hydrolysis for bagasse generation. The twelve scenarios for extracting nanocrystals that were investigated consisted of treatment with sodium hydroxide or sodium chlorite followed by sulfuric acid hydrolysis. All products and processes were characterized by their yield and X-ray diffraction. As a result, all scenarios showed that the pretreatment stage was the most important contributor to the environmental impact. The comparison among the scenarios showed that nanocrystals produced by processes V – NaClO2/NaOH/H2SO4/30min/1x and IX – NaClO2/NaOH/HNO3/H2SO4/30min/1x presented low water consumption and minimal contributions to climate change. Therefore, considering the LCA, yield and crystallinity, the best processes were V and IX sequences. Finally, these cellulose nanocrystals were evaluated by their chemical composition, morphology and thermal stability, exhibiting hemicellulose and lignin removal, nanometric dimensions from 8 to 12nm, high crystallinity and low thermal stability.