Why grow asparagus in sea water?
 

Salt-tolerant plants purify process water from fish farming

Almost half of the saltwater fish we consume today are produced in fish farms. Overfishing of oceans and, at the same time, the steadily growing demand for marine food fish are creating a boom in commercial fish farming. In addition to coastal aquaculture, a handful of projects are also being conducted on land-based salt-water fish production. In these projects, schooling fish such as sea bass, gilthead and mackerel are bred in large fish farming tanks that have no access to the sea and that are independent of natural sea water.

An innovative project in which Leibniz Universität Hannover is involved investigates purifying process water from fish farms using salt-tolerant plants such as sea asparagus and sea aster, using the nutrients and then feeding the water back into the fish farms. Consequently, a closed loop is generated in which the expensive, artificially produced sea water can be used again and again.

The great thing about it is that the plants do not only act as bio filters, but also serve as food. “We want the plants to have a good sales potential as food and have therefore sought to choose them carefully,” reported project leader Professor Jutta Papenbrock and doctoral candidate Anne Buhmann from the Institute of Botany at Leibniz Universität Hannover. They chose salt-tolerant plants that are a popular food in other regions or even considered a delicacy: so-called sea asparagus, also called glasswort, sea aster and buck’s horn plantain. Glasswort is collected in the coastal areas of France and sold as a vegetable in restaurants and on markets. Sea aster and buck’s horn plantain, which is similar to rocket, can be steamed as a vegetable or eaten raw as a spicy salad.

In an experimental basin in Hannover, experts are testing how to cultivate plants using process water from fish farming – not only on gravel or sand, but also on polystyrene boards that float on the water. The results will be implemented on a larger scale at a fish/plant closed-loop farm in Saarland. There are plans to build a 300 square metre greenhouse in association with a fish farm in Völklingen. The partners involved in the project, funded by Deutsche Bundesstiftung Umwelt (DBU), include Hochschule für Technik und Wirtschaft of the Saarland (University of Applied Sciences) and the company Neomar. Freiburg Öko-Institut e.V. (Institute for Applied Ecology) will assess the project with regard to its sustainability.

What is the situation concerning the food quality of plants that have been fed by “waste water”? Here, scientists can give the all-clear. “There are no harmful substances in the water,” Professor Papenbrock stated. Antibiotics are not used in closed-loop farming, unlike in open-loop systems in Vietnam or India. “My dream would be to transfer the idea to the tropics. In such regions, antibiotics and chemicals could be decontaminated using plants as bio filters and catalysts.”

Notes for Editors:

For further information, please contact Professor Jutta Papenbrock, Institute of Botany, phone: +49 511 762 3788; e-mail jutta.papenbrockbotanik.uni-hannover.de, who will be pleased to assist.

Meldung vom 21.12.2012