|Colt, John - National Oceanic & Atmospheric Administration (NOAA)|
|Summerfelt, Steve - Freshwater Institute|
|Fivelstad, Sveinung - Bergen College|
|Rust, Michael - National Oceanic & Atmospheric Administration (NOAA)|
Submitted to: Hatchery International Magazine
Publication Type: Trade Journal
Publication Acceptance Date: 10/28/2009
Publication Date: 11/28/2009
Citation: Colt, J., Summerfelt, S., Pfeiffer, T.J., Fivelstad, S., Rust, M. 2009. Addressing Sustainability: Energy consumption of two Atlantic salmon smolt hatcheries. Hatchery International Magazine. p.34-36.
Technical Abstract: Commercial aquaculture is driven by production costs and economic returns, but conventional economic analyses do not typically include societal costs due to ecological or environmental change, thus actual production costs may be seriously underestimated. Sustainability implies that food production should be as efficient as possible and have minimal adverse environmental impacts. Different food production systems have different labor, energy, and physical components. To compare systems from a perspective of sustainability it is necessary to evaluate the components of each system using some type of “common currency”. One approach is to do an energy analysis as the common currency. Energy analysis is a form of accounting that considers both the direct and indirect energy used in a given process, plus any energy used in transportation. The annual energy consumption of a process or component can be expressed in Mega Joules (10 6) or Tera Joules (10 12) per year. Direct energy is the energy (diesel, gas, electrical) needed to power a process or contained in a component. Indirect energy is the energy used to produce a component, for example, salmon feed contain 23.4 MJ/kg. Two systems were considered: flow-through with a gravity fed water supply, and a reuse system. Production capacity for these systems is 192,000 kg/yr of 80 g smolts. A food conversion ratio of 1.1 and a growth rate of 1.o5 were used for the models. Temperature of the flow-thru system ranged between 5-15 degrees C and a constant 1 degrees C was used in the reuse system. The flow –thru production cycle was 364 days and 231 days in the reuse system. Maximum rearing density at time of smolt transfer was 40 kg/m3. Feed, oxygen, electrical and fuel usage were estimated on a weekly basis and summed over the entire production cycle. The total energy requirements of the flow-thru system was 42 TJ compared to 55 TJ for the reuse system. Electrical and fuel energy is the largest single component comprising 54% and 68% of the total energy requirements of the systems respectively. Together, feed, fuel, and electricity account for 91-96% of the total energy requirements. The energy efficiencies range from 3.5% for the flow-thru system to 2.6% for the reuse system. The selection of the “best” sustainable system may require trade-offs between the different performance measures of each system, including capital and operating costs.