Biochar Derived from Pyrolysis of Common Agricultural Waste Feedstocks and Co-pyrolysis with Low-Density Polyethylene Mulch Film

Purpose Agricultural wastes are generated globally in large quantities, and can be converted into value-added products. Agricultural mulch films (AMFs) are also used to control soil moisture and weed growth, but present challenges because waste management is generally limited to landfilling and incineration. Pyrolysis offers more sustainable pathways by transforming mixed agricultural wastes into co-products including biochar. We explored the characteristics of biochar generated from pyrolysis of agricultural wastes and co-pyrolysis of these wastes with AMFs. Methods Representative biomass-based waste feedstocks (woody biomass, pallet wood and cardboard) were converted into biochar using a laboratory furnace operated from 500 to 800 degrees C in a nitrogen environment. Selected materials were also co-pyrolyzed with low-density polyethylene (LDPE) mulch film material at biomass-to-LDPE mass% ratios of 95:5 and 75:25. Biochar materials were characterized through an extensive measurement protocol. Results We found that all biomass waste materials produced biochar with high organic carbon content, low hydrogen-to-carbon ratio, and low concentrations of heavy metals and other contaminants, thus indicating their suitability for soil amendment applications. Co-pyrolysis with LDPE mulch film had a relatively small impact on critical biochar properties, suggesting that most of the products of plastic pyrolysis were released in the gas phase. Conclusions Based on the empirical results combined with techno-economic analysis, a farm-based co-pyrolysis system can maximize economic benefits by processing feedstock collected from regional farms in close proximity. However, achieving positive net profit requires high biochar value. [GRAPHICS] .