Improved fuel characteristics of cotton stalk, prosopis and sugarcane bagasse through torrefaction

Torrefaction is a rational method for improving the properties of biomass as a fuel. It consists of a slow heating of biomass in an inert atmosphere to a maximum temperature of 300 °C. Torrefaction yields a solid uniform product with lower moisture and higher energy content compared to those of the raw biomass. This work contributed to the development of torrefaction process at 300 °C for 1 h for cotton stalk, prosopis and sugarcane bagasse biomass which improved gross caloric value (27–41%), decreased moisture and volatile content (3.3–5.8% and 14–18% respectively), improved fixed carbon (9–24%) and reduced weight (27–46%). Statistically significant increase in calorific value and decrease in moisture content (p = 0.015 and p = 0.024, respectively) were observed by torrefaction of the biomass. There was a marginal decrease in bulk density being highest in cotton stalk (0.08 g/cm3). Energy gain of 0.47 cal/g by torrefaction was noted in prosopis with no difference in ash content. Therefore, prosopis should be considered as potential biomass for torrefaction and can be used as biofuel. Further, torrefied biomass being hydrophobic in nature, is easy to handle during storage and transportation without significant changes in biofuel characteristics.

Research highlights
► Biomass can be an important energy source to create more sustainable society.
► Nature has created large diversity of biomass with varying specifications.
► Torrefaction of biomass removes moisture and densified energy content.
► Torrefaction process overcomes economics in large scale sustainable energy solutions.
► Torrefied biomass is easy to handle for storage and transportation with on loss in biofuel characteristics.