Pilot scale evaluation of fuel pellets production from garden waste biomass

Pelletization of garden waste, without additional binder, was investigated to produce high quality fuel pellets for energy utilization. The influence of pelletization parameters viz. feedstock moisture content (5, 15, 25, and 35%), milling size (25.4 and 6.25 mm) and die size (12 and 15 mm) on pellet quality and pelletization process was studied. The results showed that the studied parameters had significant effect on pellet quality. A reduction in average durability value (95.0% to 92.5%) was observed when moisture content of garden waste increased from 5% to 15%. Appropriate regression models were also developed for each quality attribute by using multiple linear regressions. Eventually, a feedstock moisture content of 5 ± 1%, milling size of 6.35 mm and die size of 15 mm were found to offer standard quality pellets with optimum throughput capacity. Scanning electron microscopy image analysis showed a closer agglomeration of biomass particles when feed materials were pelletized at low moisture content. The equilibrium moisture content due to adsorption for garden waste pellet was found to be 14.6% which was quite low as compared to other feedstocks. Furthermore, we deduced from the combustion test that garden waste pellets may be conveniently used in a residential cookstove. In a nutshell, pelletization of garden waste biomass has been demonstrated at pilot scale in this study.