Microalgae Cultivation from Animal Production Exhaust Air: Mitigate Air Emissions and Recovery Nutrients

Abstract. Reducing air emissions and recovering nutrients from animal feeding operations (AFOs) are important to advance the sustainability of agriculture, food systems, natural resources, and rural communities. Conversion of NH₃, CO₂, and particle-phase nutrients from AFOs to microalgae is a new mitigation option. However, the proof of concept has yet to be demonstrated. To satisfy two prevalent needs, the need to mitigate air emissions and yield valued-added products, this study investigated the use of exhausted air from AFOs as nutrient sources for microalgae cultivation. Three microalgae strains, Chlamydomonas reinhardi, Scendesmus sp., and Chlorella vulgaris, were cultured using the exhaust air. When exhausted air from confined poultry housing was used as sole nutrient sources, the double times (t_d) were 1.17 d, 1.02 d, and 1.61 d for Scendesmus dimorphus, Chlorella vulgaris and Chlamydomonas reinhardi, respectively. When exhausted air from stored poultry and cow manure was used as nutrient sources, Scendesmus dimorphus showed similar growth performance as standard Bristol medium, and the double time was around 2.0 d. Exhausted gases (H₂S, VOCs) did not inhibit the growth of microalga. This study demonstrated that integrating microalgae cultivation with animal production air emissions mitigation is technically feasible, and exhausted gases can provide essential nutrients for microalgae culture. In the future scale-up systems, carbon and nitrogen sequestration and microalgae production may help reduce AFOs air emissions, earn carbon and nitrogen credits, and generate employment for rural communities.