Low carbon footprint of Nile tilapia farming with recirculation aquaculture

Recirculation aquaculture (RAS) holds promise for meeting the growing demand for high-protein food while reducing environmental impact. However, RAS contributes to greenhouse gas (GHG) emissions, especially due to its intensification. We demonstrate that most emissions from a RAS-based Nile tilapia farm originate from the water treatment systems (biofilter) and that the emission intensity is lower than other animal protein sources. CH4 emissions increased in the biofilter as the cycle progressed due to the organic matter fueling CH4 production, while CO2 emissions decreased due to primary production. We observed higher ebullitive than diffusive emission, and a lower CH4 diffusive emission during aeration. We estimated direct emissions of 2.03 kg CO2eq/kg of protein. The biofilter accounts for approximately 98 % of the direct emissions, with total emissions mostly driven by indirect emissions (infrastructure). Our findings will inform improvements in RAS aimed at reducing emissions from water treatment and lowering emissions from protein production.