New research on power consumption in recirculating aquaculture systems
In a review article, a group of Australian and American researchers have looked for patterns in electricity use in land-based fish farms, with the goal of making them more resource-efficient.
Recirculating aquaculture system (RAS) facilities are known to be water and nutrient efficient, but they are also energy intensive.
A study conducted by researchers aimed to identify, review, and summarise current knowledge about key trends and reported factors affecting the consumption of electricity in RAS, as well as to examine how resource use is reported.
For this purpose, energy use in RAS for fish was investigated in 25 studies from 2010 to 2024.
These studies showed that the largest energy consumers in RAS operation are water pumping, temperature control, filtration, and aeration or oxygenation. Some studies show that pumping and moving water accounts for up to 45% of the total energy demand in the RAS facility, while other studies attribute more than half of the energy consumption in the facility to temperature control.
Aeration
In addition, aeration and oxygenation account for 9-37% of energy consumption, depending on the system. Furthermore, some studies show that up to 16% of total energy consumption has been attributed to UV disinfection in addition to energy used for skimmers, drum filters, and denitrification.
“This diversity in system design and operation leads not only to varying energy use but also to variations in water consumption and feed conversion in each system,” the researchers write.
“However, reliable and updated knowledge on how energy use relates to other key resource demands such as water consumption and feed conversion, remains scarce, limiting researchers, engineers, and practioners in their ability to optimally design and operate RAS.”
Understanding these variables and how they affect performance in RAS is, according to the researchers, crucial for optimising resource use and improving sustainability in modern fish farming.
Energy consumption per kg
Their overview provides a systematic synthesis of published data on energy use in fish farming in RAS between 2010 and 2024, with particular emphasis on electrical energy use per biomass produced, defined as the amount of electric energy needed to produce 1 kg of fish biomass at farm gate and recorded in kWh/kg fish.
It assesses how energy needs are reported across studies, and how this relates to other key resources, such as water consumption per biomass produced and feed factor.
Furthermore, the study aims to investigate how system design, nature, and operating practices can affect performance.
“By providing a standardised basis for comparison, this overview not only brings together the current state of knowledge, but also highlights methodological inconsistencies and points to priorities for future research to strengthen the sustainability of RAS. Once this is achieved, the design and engineering of RAS can be carried out on a basis that is more consistent with the research. Furthermore, it will be possible to homogenise research results and make it easier to compare findings, which will contribute to better RAS research,” they write.
Conclusion
The researchers write that contrary to expectations, the study, based on available data, could not confirm any relationship between energy use, water consumption, and feeding in RAS for fish.
“Due to variation in how data is reported - with different formats, units of measurement and methods - it is difficult to draw broad and generally valid conclusions. In order to meaningfully investigate the relationships between energy use, water consumption and feeding in the future, data collection and dissemination must be standardised so that it is possible to draw robust conclusions. Until these differences are addressed, comparisons will remain challenging,” it is said.
Despite the limitations, the researchers believe that the systematic review they have prepared contributes to an increased understanding of energy use in RAS in recent years.
High-yield species
“It shows that the sector is exploring high-yield, high-density species for commercial production, to manage costs and operate more efficiently.”
Another finding showed that commercial RAS have lower energy use than research facilities, and freshwater facilities were more energy efficient than saltwater facilities.
At the same time, the field currently lacks the data standardisation necessary to establish a robust benchmark for energy use.
“Future studies should follow a minimum level of data reporting, as recommended by the authors in this study, to make future research more consistent. Once this is in place, comparable benchmarks for energy use can be established, which will support better-informed decisions in design, operation, management and policy-making for the further development of RAS,” they conclude.
