The Mitigation of Gaseous Emissions from Swine Manure: A Review of Biochar Application for Environmental Management

<b>Abstract.</b> The livestock industry plays a significant role in the economic well-being of the U.S. The industrial output comes with a host of environmental challenges. Key amongst them is handling the gaseous emissions emitted from livestock manure. As such, mitigation of gaseous emissions from livestock operations such as odor, odorous volatile organic compounds (VOCs), ammonia (NH₃), hydrogen sulfide (H₂S), greenhouse gases (GHGs) have been of great research interest for the last couple of decades. Technologies for mitigating gaseous emissions are being developed as a part of environmental management. Biochar, a low-cost byproduct of biorenewable energy and thermal waste processing, has been actively researched as a potential surficial treatment to livestock manure. The effectiveness of biochar treatment on mitigating gaseous emission from manure differs, likely because of the influence of many confounding factors. Therefore, this review aims to summarize and highlight current research related to mitigating gaseous emissions from manure treated with various types of biochar and its properties. Various modes of biochar applications, e.g., manure additives, dosage, and timing, are discussed in the context of emissions mitigation. The potential synergy between mitigating emissions and improving manure quality for future field applications is presented. Biochar can be a comprehensive solution to gaseous emissions while also upgrading manure as a high-quality fertilizer that could improve the sustainability of animal and crop production systems. However, standardization and certification of biochar properties suitable for specific environmental management applications are recommended.