Suppression of carbon footprint through the CO2-assisted pyrolysis of livestock waste

Abstract

Concentrated animal feeding operation facility in modern livestock industry is pointed out as a point site causing environmental pollution due to massive generation of manure. While livestock manure is conventionally treated through biological processes, composting and anaerobic digestion, these practices pose difficulties in achieving efficient carbon utilization. To address this, this study suggests a pyrolytic valorization of livestock manure, with a focus on enhancing syngas production. Hen manure was particularly chosen due to its abundance of calcium carbonate (CaCO3) compared to other mammalian livestock, exhibiting distinctive thermolytic behaviours. The thermolysis of CaCO3 in hen manure releases carbon dioxide (CO2), simultaneously served as a partial oxidant for the carbon monoxide (CO) enhancement. To further evaluate the effectiveness of CO2, hen manure was pyrolyzed under the presence of CO2. The use of CO2 demonstrated a gas-phase interaction with hen manure-derived volatiles, re-allocating the pyrogenic products into CO-rich syngas. To accelerate the reaction kinetics of CO2, catalytic pyrolysis over a supported Ni catalyst was conducted, further enhancing CO-rich syngas. To assess the environmental advantages, the carbon footprints under various pyrolysis conditions were estimated by confirming the energy consumption and CO2 mitigation potential of pyrogenic products. Therefore, this study highlights that the CO2-mediated pyrolysis of hen manure globally generated offers a potential to mitigate 934.67 million tons of CO2 in annual.