Production of solid fuel biochar from waste biomass by low temperature pyrolysis

Low temperature pyrolysis was employed to produce solid fuel biochars from woody (pine wood) and non-woody biomass (coconut fiber) in the present study. Chemical evolution of biomass under pyrolysis conditions was determined and fuel qualities of the biochars were evaluated including energy densities, ash-related problems and combustion behaviors. The results showed that dehydration reaction of the biomass had same preference with decarboxylation reaction under pyrolysis conditions. The hemicellulose and cellulose in non-woody biomass showed faster decomposition than those in woody biomass. The biochars derived from coconut fiber showed lower energy densities and energy yields than those from pine wood under identical conditions. All major ash forming metals originally contained in raw biomass were accumulated in the resultant biochars and more serious slagging and fouling problems were present during combustion of pyrolytic biochars compared to raw biomass. The reactivity of biomass decreased and the main mass loss shifted to elevated temperature zone with the increasing pyrolysis temperature, indicating increased thermal efficiency and environmental benefits were achievable during biochar combustion compared to raw biomass combustion. Taking into account combustion characteristics and energy yield, optimal pyrolysis temperatures for solid fuel production were around 300 °C for coconut fiber and 330 °C for pine wood.