Agro-industrial Waste Upgrading via Torrefaction Process – A Case Study on Sugarcane Bagasse and Palm Kernel Shell in Thailand

In this research, the upgrading of agro-industrial wastes was investigated by using the torrefaction pretreatment technique. Two types of biomass waste, including sugarcane bagasse (SBG) and palm kernel shell (PKS), were used as raw materials. The operating conditions, i.e., torrefaction temperature and residence time, are between 225-300oC and 30-60 minutes. The findings show that, in terms of mass yield and calorific value of the solid product, the torrefaction temperature is a more sensitive parameter than the residence time. By increasing the torrefaction temperature from 225 to 300oC, the mass yields are dropped in the range of 28.79-31.57 wt.% and 28.00-29.88 wt.%, while the effect of holding time exhibits the mass yield decreasing only 3.12-5.90 wt.% and 1.53-3.41 wt.%, for SBG and PKS torrefaction, respectively. In terms of calorific value, higher heating values increase as torrefaction severity increases, varying in the range of 0.29-2.84 MJ/kg, with torrefaction temperature as the dominant factor. Regarding the calorific value, energy yield, energy gain, and energy-mass co-benefit index, the optimal operating conditions for SBG and PKS torrefactions are the same condition as 275oC for 90 minutes. SBG and PKS bio-coals obtained from torrefaction are promising solid fuels with high calorific value (about 23 MJ/kg), with an energy yield of 73.93-77.41%, relative to coal that could be further utilized for co-firing in thermal power plants