Implementation of a Biogas-system into Aquaponics : Determination of minimum size of aquaponics and costs per kWh of the produced energy

Abstract: Aquaponics might be one solution to produce food in a more sustainable way in the future. Aquaponics combines aquaculture and hydroponics in a way that the disadvantages of one system become the advantages of the other one. The nutrient rich excess water from the fish tank is used for plant growth, while the plants are used as biofilter to clean the water for the fish. Further closed loops can be created by using plant-residues, sludge and food wastes as raw materials for a biogas digester. With a combined heat and power plant (CHP) the produced methane can be used for heat and electricity production needed by the aquaponics. This report determines if such implementation can lead to reduced overall running costs and which size the aquaponics should have. As example location Sweden is chosen.It shows that the methane demand of a CHP requires a minimum size of the biogas digesters and aquaponics. In the aquaponics at least 50 t of fish have to be bread with a complementing grow bed area of 800 - 900 m2. In total the aquaponics system contains 1000 m3 water. The Energy produced by the CHP will not cover totally the energy demand of the aquaponics-system and should be complement by energy from other sources (e.g. solar cells, wind turbines) if there is no access to a stable external energy supply. Energy produced by the CHP has an average price between 1 - 2.1 kr/kWh. If no CHP is implemented, there is no minimum size required for the aquaponics- and biogas-system and the produced methane can be used for heating and cooking.