Aquaculture Waste Management, Water Quality, and Methane Emissions: Implications for Environmental Sustainability in Intensive Tilapia Farming

Methane (CH4) emissions from aquaculture can be enhanced by organic waste accumulation and oxygen-limited conditions, yet field-based emission estimates remain scarce, particularly for intensive tilapia production in above-ground tanks in Brazil. This study evaluated how aquaculture waste composition and oxygen availability affect CH4 emissions and quantified emissions from a commercial intensive Nile tilapia production system. A controlled experiment assessed water and sediment characteristics and CH4 emissions during decomposition of feed, feces, and fish carcasses under contrasting residue combinations and aeration conditions. Field measurements quantified diffusive and ebullitive CH4 fluxes from production tanks and a sedimentation pond during 13 sampling campaigns conducted between February 2023 and November 2024. The non-aerated treatment receiving mixed residues showed the highest CH4 emissions, whereas aeration reduced mean flux by approximately 98.8%. At commercial scale, emissions were concentrated in the sedimentation pond and dominated by ebullition, while emissions from aerated production tanks were negligible. Annual CH4 emissions were estimated at 325.9 kg CH4 ha−1 yr−1, corresponding to 8799 kg CO2-eq ha−1 yr−1 and 0.147 kg CO2-eq kg−1 fish produced during the nursery phase. These findings identify oxygen availability and waste accumulation as key targets for CH4 mitigation through aeration and improved residue management, providing insights into strategies to reduce the environmental impact and support the sustainability of intensive tilapia production.