Indoor paddy farming presents a promising solution to food security challenges, offering controlled environments for optimised crop growth. However, maximising yield efficiency requires a thorough understanding of microclimatic factors including carbon dioxide (CO₂). This study employs Computational Fluid Dynamics (CFD) to evaluate the effects of additional CO₂ supply on airflow dynamics, CO₂ distribution, and plant growth conditions in an indoor paddy farming setup. Two settings are examined, one with ambient CO₂ levels and the second with targeted CO₂ enrichment. The CFD model incorporates realistic paddy plant structures and simulates transpiration, energy exchange, and CO₂ absorption processes. By defining precise boundary conditions for temperature, humidity, and gas exchange on the leaf surfaces, the model enables detailed analysis of CO₂ transport inside the cultivation space (paddy beds) with the help of a small-scale controlled air capture device, inspired by direct air capture (DAC) technology. It is indeed promising that the CO₂ enrichment through controlled air capture enhances uniformity in gas distribution as well as optimising concentrations around the rice canopy, which can boost photosynthesis and biomass accumulation. Contrariwise, the second setting (without CO₂ enrichment) displays areas of restricte plant growth which reduces the overall yield. With the exploration of the effects of controlling ventilation on CO₂ retention and distribution, the findings suggest that an integrated CO₂ delivery system with optimised airflow patterns potentially mitigates stratified flow issues, and therefore it further maintains stable concentrations across the paddy beds as well as enhancing evapotranspiration processes, which creates a balanced microclimate for the plants. This research demonstrates the potential for exploring innovative indoor farming design strategies, particularly for maximising yield efficiency of staple agri-foods like rice using CFD analysis. Through CO₂ enrichment and airflow optimisation, the indoor farming technique potentially maximises its profitability through high yield production and simultaneously reduces resource consumption and uncertainties due to external climatic fluctuations.