Chikako Asada
The utilization of plant biomass as a resource of producing fuel and materials instead of fossil resources, i.e. oil, coal, and natural gas, can reduce CO2 emission and realize a low carbon society. The autohydrolysis treatment with high pressure and high temperature, a thermochemical pretreatment method for plant biomass, is a chemical-free method because it only uses hot steam. This study proposed a new effective and environmentally friendly biorefinery system of unutilized plant biomass, i.e. waste Bo-de chopsticks, using the autohydrolysis treatment followed by milling treatment, and then water and acetone extractions. The water extract, the acetone extract, and the residue after the extractions obtained from the autohydrolyzed waste Bo-de chopsticks were converted into methane gas, lignin epoxy resin, and cellulose nanofiber. The water extract and the residue after the extractions were used as substrates for the methane gas production. Furthermore, after bleaching the residue after the extractions, it was used as a raw material for producing a cellulose nanofiber (CNF) as shown in Figure 1. The maximum specific tensile strength of CNF, i.e. 110 MPa/(g/cm3), was obtained at a steam temperature of 200oC (a steam pressure of 1.5 MPa) and steaming time of 5 min. The acetone extract, a low molecular weight lignin, was used not only a raw material of epoxy resin but also a curing agent. The almost lignin-derived cured epoxy resin showed a good thermal and mechanical property required in the electronic material field. This biorefinery system in this work seems to be very useful for the total effective utilization of not only waste Bo-de chopsticks waste but also other un-utilized plant biomass.