Utilising Torrefaction to Determine the Fuel Characteristics of Forestry and Agricultural Biomass for Solid Biofuel

The use of coal has declined owing to growing concerns regarding environmental pollution worldwide. Biomass is becoming a feasible alternative to coal, particularly for the continuous generation of agricultural biomass. However, the low heating value of biomass limits its widespread use. Torrefaction may help overcome the restriction of biomass. Methods: This study performed torrefaction on soybean husks, maize cobs, rice straw, pruned grape branches, wood pellets, and bamboo. Torrefaction was done at 230–310 ℃ for 30 or 60 min.

The mass yield ranged from 35.62% to 93.59%, depending on the biomass type and process variables. The mass yield and severity factor were positively correlated with correlations ranging from 0.7074 to 0.9345. Moreover, the fuel properties changed, wherein mass loss, fixed carbon, and volatile matter changed slightly in the wood pellets. In contrast, increasing the treatment temperature and duration heightened the fixed carbon content and decreased the volatile matter content of the remaining biomass. Elemental analysis showed an increase in carbon content and a decrease in hydrogen and oxygen contents. Some torrefied biomasses have a low combustion index, which may make fuel usage difficult. Generally, enhancements in conventional biomass were evident.

This study demonstrated that the process of torrefaction led to improvements in biomass fuel properties.