No 14 July/August 2012
18 research*eu results magazine — N° 14 —July/August 2012 ENVIRONMENT AND SOCIETY
Innovative pellets to benefit organic farmers
Researchers in Germany and Hungary have engineered novel pellets that are able to repel pests in a way that does not harm the environment but could fertilize the plants. These pellets are made of cyanobacteria and fermentation residues from biogas facilities.
The purchase and consumption of organic vegetables continues to grow, with many people acknowledging that they prefer to buy and eat products that are neither treated with pesticides nor laden with chemicals. But organic farmers must deal with the challenge of keeping their plants safe from pests, a task that is next to impossible. So when cabbage root flies, for instance, lay their eggs in spring and autumn on freshly planted greens, an entire harvest can be lost. Now there is some good news for these farmers, thanks to scientists from the Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB), working in collaboration with researchers from the University of West Hungary in Mosonmagyaróvár and on behalf of several organic agriculture associations.
The organic farming industry should benefit from this novel development since organic farmers stand to lose entire crops when pests, such as cabbage root flies, lay their eggs on freshly planted vegetables.
‘The pellets primarily consist of fermentation residues from biogas production, but they also contain 0.1 % cyanobacteria,’ says Dr Ulrike Schmid-Staiger, group manager at IGB. Soil flora degrade the cyanobacteria, which release a scent that repels cabbage root flies, after the pellets are placed around the vegetable plants. The fermentation residues, which are rich in nutrients, also fertilize the plants.
The team employed a flat-panel airlift reactor, originally developed for micro algae, to culti- vate cyanobacteria. They used only light, carbon dioxide (CO2) and mineral nutrients to cultivate the bacteria. The task was not easy, especially because the bacteria had to be mixed thoroughly and allowed to rise to the surface. Both air and CO2 had to flow into the reactor. It should be noted that the cyanobacteria are very sensitive. Their structure looks like a long string of pearls, which can be damaged if too much pressure is placed on it. The researchers regulated the air inflow to allow the mass to be thoroughly mixed without damaging the bacteria.
They later used super-heated steam to dry the cyanobacteria, which was then mixed with the fermentation residues and pressed into pellets. The team acquired the fertilizing fer- mentation residues from organic farms in which liquid manure is decomposed into biogas. Within two weeks, they generated 300 litres of biogas per kilogram of organic dry mass. Any remnants that cannot be further fermented are dried.
The pellets were tested in open-field studies in Spain and Hungary, where the researchers found that the cabbage root flies did not attack any of the growing cabbage or kohlrabi.
The study was coordinated by the Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB) in collaboration with researchers from the University of West Hungary.
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