Distributed biomass pyrolysis equipment applied in the field of yard waste treatment: equipment design, recycling of by-products, physico-chemical analysis of products, economic efficiency analysis

To convert yard wastes including bamboo waste and wood waste into solid biofuel, a distributed biomass pyrolysis equipment was designed with the characteristics of recovering bio-tar, waste heat utilization and high efficiency in this research. Hydroxypropyl methyl cellulose (HPMC) and recovered bio-tar were utilized as a composite binder for molded charcoal. The mechanical, combustion, ash fusion characteristics and economics of molded charcoal were evaluated. The optimized operating conditions for the equipment included a pyrolysis temperature of 400 °C, a heating rate of 2.5 °C/min, and a holding time of 30 min. The yield of bamboo charcoal was 36.37 %, while the yield of wood charcoal was 34.20 %. The optimum mass ratio of HPMC to bio-tar was 3:1. At this ratio, the HHV of molded wood charcoal was 25.47 MJ/kg, with a compressive strength of 172.25 N/cm. Similarly, the HHV of molded bamboo charcoal was 25.88 MJ/kg, with a compressive strength of 143.38 N/cm. The minimum selling price (MSP) of molded charcoal was 861.96 USD/t with a profit of 5.14 USD/t. Consumable expenditure, labor cost, and yard waste cost were the major factors influencing the MSP of molded charcoal. These findings will provide scientific guidance for value-added utilization of yard wastes.