New Uses for contaminated grass from Elbe River meadows

Leuphana is developing ideas for the flood plains contaminated grass material well suited as soil conditioner.

The Elbe floods deposited sludge, contaminated with heavy metals and dioxins, on agricultural fields and meadows between the river’s dikes. A research group headed by Prof. Dr. Brigitte Urban at Leuphana University of Lüneburg is currently investigating the exact level of pollution in the sedimentation on the flood plains. Together with their partners, the researchers are working on developing a technique with which the contaminated grass material could be processed into biochar, which would break down the pollutants along the way. This material, if enriched with nutrients, could then be used in agriculture as a soil conditioner.

“We are working with the assumption that the floods have deposited a comparably large amount of sludge on the meadows located along the banks of the river,” Frank Krüger, a biologist in Professor Urban’s research group, said. The ground was already heavily contaminated before the floods at the end of May and the beginning of June 2013: in 2012 dioxin levels were measured that, at the highest readings, were 35 times the generally acceptable level for agricultural use of the meadows (40 nanograms per kilogram of soil). In order to prevent the transfer of contaminants into the human food chain, officials recommended that the meadows be grazed for only a few weeks at a stretch.

No less than around 4,500 of the approximately 6,000 hectares along the middle Elbe’s flood zone in Lower Saxony is used as pasture land. For decades, Krüger said, dioxin contamination of these fields has been a problem for farmers. They need grass and hay as animal feed. Yet the environmental pollutant dioxin cannot, practically speaking, be broken down, instead it settles in plants and high-fat everyday foods such as eggs, milk and meat, according to Krüger.

With their new research project, “Activated Biochar,” part of the EU-regional development project, Leuphana’s Innovation-Incubator, the scientists aim to develop, together with their partners, a method whereby these fields nevertheless can be used. The contaminated grass cuttings first will be used to produce biochar. The scientists are convinced that the dioxin will be completely broken down in the process. Next the biochar can be made fertile by adding nutrients from biocompost, liquid manure or dung, thereby forming a new soil conditioner which can replace artificially produced mineral fertilisers.

On this project Leuphana’s scientists are working together with the Lower Saxony biosphere reserve administration, Elbtalaue, the Wendland companies ERDE Innovation, the ERDE Institute and the Count of Bernstorff Enterprises, as well as the Rhineland-Palatinate biochar producer, Pyreg. Preliminary investigations indicate that the new procedure has good prospects for success. On top of that, the new fertilizer is also climate-friendly: during the production of biochar, the CO2 from plants bonds and does not escape into the atmosphere again.

Lüneburg’s researchers and their partners are convinced that the new procedure could open up all the flood plains on the Elbe from Dessau to Hamburg for new uses.