FireBox and CharBoss: An alternative to open burning of woody biomass

Abstract

Open burning is commonly used to dispose of piles of forest residues generated by forest management activities; however, this method is associated with smoke emissions and damage to forest soil. Air curtain burners (ACB), such as the Firebox (FB) and CharBoss® (CB), offer an alternative to open burning. This study evaluated the performance of FB for biomass disposal and CB for biomass disposal and biochar production with the objective of quantifying the benefits and limitations of each machine. Ponderosa pine biomass obtained from harvesting after a wildfire event and freshly cut wood from ponderosa pine trimmings were used to evaluate the performance of each machine. We measured the combustion rate for both machines and biochar produced from CB. The burning rate for large-diameter (>10 cm) biomass using FB machine was 1.1 GT/h (924 ◦ C) while small-diameter (<5 cm) biomass burned at the rate of 2.4 GT/h (814 ◦ C), and for biomass consisting of mixed-sized materials it was 2.5 GT/h with the highest recorded temperature of 1089 ◦ C. The biochar yield from CB operations ranged between 8.8 % and 17 % on a bone-dry ton basis. The size of biomass material, machine type and moisture content influenced the burning rate. The FB is most appropriately used in a centralized setting where large quantities of biomass are available near harvest operations, while the CB is better used for biochar production in a mobile setting. These results are useful for understanding alternative biomass management options, the long-term financial implications, and environmental benefits.