Microalgae cultivation using ammonia and carbon dioxide concentrations typical of pig barns

While global population growth drives increased production efficiency in animal agriculture, there is a growing demand for environmentally friendly practices, particularly in reducing air pollutant emissions from concentrated animal feeding operations. This study explores the potential of cultivating microalgae in photobioreactors (PBRs) as an eco-friendly and cost-effective approach to mitigate NH₃ and CO₂ emissions from pig barns. Unlike traditional physicochemical mitigation systems, microalgae offer a renewable solution by converting pollutants into valuable biomass. The research focused on Scenedesmus dimorphus growth under typical NH₃ and CO₂ concentrations found in the indoor air of pig barns. Four NH₃ (0, 12, 25, and 50 ppm) and four CO₂ concentrations (350, 1200, 2350, and 3500 ppm) were tested using photobioreactors. Results showed a maximum specific growth rate of 0.83 d^-1 with 12 ppm NH₃ and 3500 ppm CO₂. The dry biomass concentration was significantly higher (1.16 ± 0.08 g L^-1; p < 0.01) at 25 ppm NH₃ and 2350 ppm CO₂ than other test conditions. S. dimorphus demonstrated the peak NH₃ and CO₂ fixation rates (23.8 ± 2.26 mg NH₃ L^-1 d^-1 and 432.24 ± 41.09 mg CO₂ L^-1 d^-1) at 25 ppm NH₃ and 2350 ppm CO₂. These findings support the feasibility of using algae to effectively remove air pollutants in pig barns, thereby improving indoor air quality.