Aquaponics: » Fresh Fish Meets Young Vegetables

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Fresh Fish Meets Young Vegetables
FIRST ATTEMPTS to combine fish and vegetable farming were carried out in the 1980s. In the meantime, the so-called aquaponics has been tried and tested in many parts of the world. The use of modern technology allows for the double use of water, nutrients, energy and land in a more resource-friendly way that is also lower in emissions. The potential applications of this breeding method are diverse. Neither fertile soils nor large amounts of water are needed.

groundwater levels, growing poverty, rapid population growth, continued rural depopulation - worldwide there are urgent economic, social and environmental problems, for which solutions need to be found. Often there are regional or alternative projects with sustainable ideas to improve the living conditions of the local people. In future, for example, aquaponics could make a greater contribution to food supply, for example in regions with difficult climatic conditions. This form of farming, which combines “aquaculture” and floating crop plant cultivation by means of “hydroponics”, is already used in many countries, including Germany. The Leibniz Institute for Freshwater Ecology and Inland Fisheries (IGB) in Berlin has been researching this procedure for about ten years. In the context of the “ASTAF- PRO” project, which is funded by the Federal Ministry for Education and Research, the researchers of the institute have developed a 170 square metre facility for resource and emission-free tomato and fish production. On the site at Lake Müggelsee, Nile tilapia - which belong to the family of the tilapias - are bred in ponds. The water in which the animals swim is also used for the cultivation of tomatoes. This eliminates the need for the disposal of waste water. First, coarser particles are removed from the liquid in the tanks, and then the liquid is routed through a bio filter. In this process, aerobic bacteria convert the ammonium eliminated by the fish through the gills into nitrite and afterwards into nitrate, which is used as a fertiliser in agriculture. On demand, the filtered water is then channelled through a one-way valve to the plants, which thrive directly in the nutrient mixture. The roots of the tomatoes absorb the nitrates among other things, thus purifying the liquid. “The special feature of our system is that we have two independent circulation systems. The flow of liquid between the two subsections is regulated by a patented system. We can establish optimal growing conditions both for the plants and for the fish. The pH value, the oxygen supply and the addition of nutrients is regulated individually,” explains Dr. Georg Staaks, the fishery engineer of the IGB, who has been researching closed recirculating systems for 20 years.

In comparison to aquaculture, it is especially the water recovery which makes aquaponics a sustainable system. Tomatoes, for example, give off up to six litres of water per day into the greenhouse air via their leaves. At IGB, this water is collected via cooling traps, cleaned, and then reinserted into the fish cycle. Due to the strongly reduced water consumption, up to 90 percent less water is needed to attain the same yields in comparison to conventional agriculture, according to calculations made by the institute. In aquaculture with conventional recirculation systems, for example, ten percent of the water needs to be replaced daily. The IGB adds three percent fresh water every day. “With 200 litres of water we are currently producing up to two kilograms of tomatoes and one kilogram of fish. In normal cultivation, 184 litres of water are needed on average for the production of one kilogram of tomatoes,” says Staaks.

Within the framework of the INAPRO research project, the IGB and 17 other partners from eight countries are also researching aquaponics procedures at an international level. INAPRO is one of eleven selected concepts seeking innovative solutions for water management and receiving millions of Euros in funding for this purpose by the European Commission. Under the auspices of the IGB, three 500 square metre demonstration facilities are currently being built, one in the north German district of Abtshagen, one in the Spanish region of Murcia and one in the eastern Chinese province of Shandong. This is where the economic viability of the aquaponics procedures developed by the institute is to be tested and improved. “INAPRO allows us to develop our own approaches together with the know-how and knowledge of many partners. Before being ready for the market, some optimisations must still be made. We want to further improve the nutrient cycling and water quality, for example,” says project coordinator Staaks. Some technological innovations are being installed to the existing systems at the four demonstration facilities. In this way, the water from the fish tanks is mechanically purified a second time in the new facilities. Even more nutrients are to be extracted from the muddy residue with the coarse particles which remains after the purification procedure. Furthermore, Staaks and his team want to test the “GrowWatch System” of the Dutch company Fytagoras. It is used for examining the plants on a regular basis, for example with regard to the moisture, the CO2 consumption and the colour of the leaves. The monitoring system then offers recommendations on how to further improve the growing conditions in the greenhouse.

IGB is also looking for a sustainable solution for the year-round operation of its aquaponics facility in Berlin: “While we are also achieving good yields and a consistent nutrient level for the fish in winter, the vegetable cultivation needs to be more flexible. We are currently considering growing different tomato varieties in each season, or switching to herbs in the cold months. The objective is the keep energy use as low as possible throughout the year,” says Staaks. The weather-related costs for heating, air-conditioning or cooling can be considerable in aquaponics facilities. The IGB uses, among other things, the energy from biogas plants or solar panels for this purpose. The institute works closely together with the research team of the project “The Low Energy Greenhouse” (ZINEG). This research cooperation develops technologies for reducing resource consumption in greenhouses and was awarded the German Sustainability Award 2014 last December for the category “Research”.

The INAPRO project will continue until 2017. In the first year of testing, approximately 10 tons of Nile tilapia and 30 tonnes of tomatoes are to be produced in each facility. In subsequent years, testing with other warm-water fish and vegetable varieties is to ensue at the individual locations. “Our test facilities have a size which is also recommended for commercial use. The target group of our procedure are more medium-sized companies which want to produce 20 to 50 tonnes of fish and 30 to 100 tonnes of tomatoes per year. These are economically realistic results,” says Staaks. IGB believes that, once they are market-ready, their aquaponics systems can initially be used on a large scale in Central Europe. The vegetables would be intended for the regional markets and have the price level of organic products. Unlike in the United States, for example, aquaponic vegetables may not be labelled as organic in the EU. The research team of IGB is hoping that its system will also be used outside of Europe in the long term. “Our systems can be built anywhere. In areas, for example, which are too dry for conventional agriculture, the closed recirculation systems need very little additional water,” says Staaks and concludes: “In regions in which the electricity supply is poor, I would refrain from using complex air-conditioning. Here the two circulation systems can only be operated with a pump. The biggest hurdle would perhaps be to convince the locals.”

text Manuela Fuchs

Pictures: 1, 2, 3, 4, 5, 6, 7, 8 = Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB