Evaluating the environmental impacts of nanocellulose production using conventional and novel approach at laboratory scale

Green chemistry promotes the design and application of chemical products and processes that reduce or preferably eliminate the use and generation of hazardous substances. The objective of this research was to evaluate the environmental performance of two methods of producing nanocellulose at the laboratory scale: (i) a conventional sulphuric acid hydrolysis that has been upscaled for industrial use (TRL 8–9); and (ii) the novel approach using the ternary eutectic mixture ChCl: pTSA: PA molar ratio (1:1:1.35) that is currently at TRL 2. The purpose of developing the new approach was to find a better alternative to the conventional process from an environmental perspective. To validate this, life cycle assessment was used to compare conventional vs novel methods with the functional unit of 1 g nanocellulose produced. The system boundary was from cradle to laboratory gate. The results were interpreted to select the best method for laboratory use and to identify design issues to address during upscaling of the novel method. For both methods, conventional and novel, the impact categories selected were climate change (kgCO2 eq), Acidification (kg SO2 eq), Ecotox Air (CTUe) and Eutrophication (kg N eq). To produce 1 g of nanocellulose with sulphuric acid caused a climate impact of between 68 kg CO2 eq (90 % yield) to 105 kg CO2 eq (57 % yield). Produced using DES the climate impact ranged from 85 kg CO2 eq.(90 % yield) to 132 kg CO2 (57 % yield). The results indicated that the novel method created greater impacts over the whole life cycle. Unless significant changes are made during upscaling, the novel method will not make a positive contribution to sustainable, circular bioeconomy. The method does have potential to be improved to reduce impact, including using decarbonised energy, a renewable, bio-based feedstock for the cellulose and choline chloride to improve the overall efficiency of using deep eutectic solvent (DES) at pilot scale. The low TRL life cycle assessment offered insights not possible if only the laboratory stage of the analysis had been considered.