Design and analysis of an innovative livestock barn for sustainable dairy farming

The dairy industry is growing rapidly with increasing population and living standards. However, dairy farms are major sources of greenhouse gas emissions because methane is released through enteric fermentation and manure decomposition. This study proposes a dairy-barn model that captures methane emissions for useful on-farm outputs while maintaining favourable conditions for cattle. The proposed barn consists of two subsystems: a heating, ventilation, and air-conditioning (HVAC) unit that provides cooling and ventilation, and an electricity-generating Brayton cycle. Methane extracted from the barn's exhaust is used as a methane-air mixture in the Brayton cycle to generate electricity. Computational fluid dynamics and thermodynamic analyses are used to evaluate HVAC performance and energy production. The system boundary is defined at the barn level, covering HVAC-based methane capture, direct methane conversion in the Brayton cycle, and gross power generation, while excluding broader system-level effects such as net cooling-generation balance, grid-related indirect emissions, and economic performance. Model results indicate that the proposed system could capture and process 18 tonnes of methane per year, corresponding to a 400.5-tonne CO₂-eq reduction in methane-attributable GHG emissions. The Brayton cycle is predicted to deliver approximately 17.8 kW of electricity under the analysed methane concentrations. Overall, the findings demonstrate the design-stage potential of integrating barn-climate control with methane utilisation as a pathway for lower-emission dairy-farm design.