Emissões de gases de efeito estufa em piscicultura em tanques suspensos com sistema de recirculação aquícola (RAS)

Abstract

Aquaculture plays a crucial role in meeting the growing global demand for protein. However, the expansion of the activity results in increased greenhouse gas (GHG) emissions. Thus, the adoption of the recirculating aquaculture system (RAS) is seen as a strategy for the sustainable expansion of aquaculture. It is estimated that the use of RAS will increase in the coming years, aiming for reduced water usage, reduced land usage, and better production control, in addition to effects on GHG emissions that are not yet well quantified. Therefore, there is a growing need to understand the GHG fluxes emitted by RAS. In this work, it was demonstrated that the major emissions in a Nile tilapia fish farm in RAS, with suspended tanks, originate from the water treatment system (biofilter) and that the total CO2eq emission is lower than other animal protein sources. It was observed that the CH4 flux increased in the biofilter as the production cycle progressed, while the CO2 flux decreased due to the density of Lemna minor and Pistia stratiotes L. Additionally, it was observed that ebullitive emission was significantly higher than diffusive emission and that there were significant differences between measurements with aerators on and off in the suspended tanks. A total of 2.97 tons of CO2eq was directly emitted by the RAS fish farm, and 2.03 kg CO2eq/kg of protein or 0.32 kg CO2eq/kg of live weight. The findings reveal that the biofilter is responsible for about 98% of the emissions and that the total emissions are mainly the result of indirect emissions (fingerling production, feed, and energy consumption). The need for further improvements in RAS is highlighted, also for other aquaculture species, aiming to reduce emissions in water treatment systems, resulting in the mitigation of aquaculture emissions.