Food production: Water, a key resource
As the growing trend towards organic and regional produce illustrates, more and more customers are now demanding sustainability not only for manufactured goods but also for the food on their plate. This is only one of a number of reasons why growers are having to adapt their way of working. Following several long dry summers and an extended period of drought, there is now a real fear that a lack of water is going to render traditional irrigation systems nonviable.
Hydroponics may provide a way forward here. This is the method – similar to the hydroculture of houseplants – by which crops are grown on an inert substrate such as rock wool and can subsist with much less water than is required in normal cultivation. In a project entitled HypoWave, researchers from Fraunhofer IGB have teamed up with partners tonmake this method more sustainable: “We looked at whethernit would be possible to use sewage from a wastewaternplant and what kind of treatment this would first require,”says Dr. Marius Mohr, head of the innovation field WaternTechnologies and Resource Recovery at Fraunhofer IGB. Case studies indicate that the most viable option is to implement such a scheme at wastewater plants that would otherwise have to expand in order to meet new and more stringent regulations. This is because the very nutrients that would have to be removed from the wastewater before it can be discharged into a watercourse are instead used for cultivating plants in a hydroponic setup. “And, what’s more, it enables us to achieve smaller and more sustainable water cycles,” says Mohr.
In arid regions such as sub-Saharan Africa, water is a scarce commodity – whether for crops, livestock or people. To make up for this shortfall, desalination – of seawater or brackish water – is increasingly the preferred solution, with reverse osmosis the method most commonly used (65 percent). Yet this technology has considerable drawbacks. “For a start, it uses a lot of energy, which in turn causes a lot of carbon emissions if that energy is generated by conventional means,” explains Dr. Lothar Schäfer, coordinator of the ICON WASTEC project at the Fraunhofer Institute for Surface Engineering and Thin Films IST. “Secondly, it requires substantial antifouling measures, which means that significant amounts of the chemicals used for this purpose end up in the sea or groundwater.” A number of Fraunhofer Institutes are working on this project. Together with the University of Stellenbosch in South Africa, they are looking to boost the efficiency of the desalination process and to develop sustainable alternatives to antifouling methods, thereby putting a stop to this source of water pollution. Further areas of interest include the development of localized desalination plants and the treatment of water contaminated with microbes for use in food production.
Water is a key factor not only in traditional agriculture. It is also vital for aquaculture, which is becoming an increasingly important form of food production. The reasons for this are twofold: firstly, our seas are largely overfished, and fishing quotas have been introduced to protect fish stocks; secondly, arable land per head of population is becoming scarce, making aquaculture increasingly important for food supply. In addition, fish have an outstanding feed conversion ratio: 1 kilogram of feed yields 1 kilo of edible fish, whereas 1 kilo of pork requires 3 kilos of feed, and 1 kilo of beef as much as 10 kilos. With current UN forecasts suggesting that the world population is likely to grow from 7.7 to 9.7 billion by 2050, this is going to become a critical factor.
Around half of all fish sold to consumers now comes from large-scale aquaculture. In many cases, this does not represent an ecological alternative to fish caught from wild stocks, since the feed residues and fish excrement associated with aquaculture increase the input of nutrients into the water. Prof. Charli Kruse, director of the Fraunhofer Research Institution for Marine Biotechnology and Cell Technology EMB in Lübeck, and his team are working on a solution: “We’re developing sustainable, land-based, closed-loop forms of aquaculture. In this case, rather than the nutrient-rich water simply being fed into the sewerage system, it is used to cultivate other organisms such as bivalves or macroalgae. We’re therefore recycling the waste from one species by using it to feed another species.” In other words, this not only filters the wastewater produced by fish farming but also creates additional produce that can boost income. This form of closed-loop aquaculture is no substitute for marine-based operations in open waters and the high earnings they generate. “But one way of cutting the environmental impact of intensive fish farming might be to populate the farmed waters with organisms that reduce the level of nutrients,” says Kruse. And this in turn would mark a further step toward achieving the kind of sustainable way of living for which young people have been taking to the streets in their Fridays for Future demonstrations.