AIR POLLUTION REMOVAL MECHANISMS IN ANIMAL HOUSING: CURRENT AND FUTURE PERSPECTIVES

This paper presents a comprehensive review of air pollution management in animal housing (livestock and poultry). It first takes stock of the key features of existing air emissions control technologies, followed by a discussion on recent advancements in tackling emerging air pollutants in these settings. Varied approaches involving physical, biological, chemical, photochemical methods are characterised by their selective efficiency in preferentially treating the prevalent air pollutants. Pros and cons of each technology are evaluated in terms of following set of key functional metrics - treatment capacity, energy efficiency, formation of inadvertent air pollutants (if any), resource demand and operational limitations. This covers well-established treatment techniques, including filtration and precipitation for particulate matter (PM); acid scrubbing for ammonia (NH 3 ); photolysis for microbial loads; caustic scrubbing for hydrogen sulphide (H 2 S); and adsorption for addressing volatile organic carbons (VOCs). Other pollutants, especially methane (CH 4 ), and certain VOCs e.g., short chain amine and phenolics are ubiquitous in animal housing and require efficient removal mechanisms. Operational challenges in deploying a single intervention to address a multitude of chemicals found in the barn air have been identified, primarily owing to the variation in their inherent treatment techniques. Hybrid physico-chemical approaches have been considered effective alternative in achieving control of diverse air emissions in livestock housing, albeit with increased resource demand and cost. Prospects for standalone treatment techniques utilising photocatalysis to degrade a broad spectrum of pollutants have been discussed as a plausible alternative to overcome this challenge. However, further improvement in photocatalysis efficiency and its relevance to the control of aerial micropollutants in animal housing has been recommended.