Upgrading agro-pellets by torrefaction and co-pelletization process using food waste as a pellet binder

This work presents a study on the properties of upgraded agro-pellets produced by torrefaction and co-pelletization process, where starch-rich food waste was used as a pellet binder. The impact of blending coal cutting waste (CCW), torrefaction pre-treatment and the use of starch binder on the mechanical properties of agro-pellets were examined. The resulting physical properties of agro-pellets were significantly improved. Thermal decomposition of corn straw (CS) can be divided into three stages. Co-pelleting with a small amount of CCW promote the combustion of CS showing an improved thermodynamic characteristic of torrefied corn straw (TCS). Torrefaction reduces the difference of heat distribution, improving the adaptability of pellet fuel in operation. Both co-pelletization and torrefaction processes lead to reduced concentrations of NOx and SO2, increased calorific value of fuel and elevated CO2 emission per unit mass, which are conducive to pollutants reduction and thermodynamic qualities of agro-pellets. Moreover, life cycle assessment (LCA) analysis indicated that more energy input was required for co-pelletization and torrefaction pre-treatment, consequently leading to an enhanced energy return ratio.