Reedbeds first purifying river water, then revitalising the withered hinterland, followed by mown reed providing heat to adjacent buildings by burning in a special oven. Researchers of Plant Research International are working on this multifunctional approach on the Lankheet Estate in Overijssel. The Waterboard is enthusiastic.
Nitrogen and phosphate concentrations are too high in countless brooks in the Netherlands. The Water Framework Directive is compelling water control bodies to lower these concentrations. At the same time, many adjacent nature areas are suffering from drought. And the chance of flooding by rivers and brooks must be reduced at the same time.
Setting up reed beds offers a solution for all three problems. Reed is lowering the nitrogen and phosphate concentration by some fifty to seventy per cent and the purified water diminishes drought problems of the hinterland. And reed beds can hold extra water in case of flooding.
But setting up and maintenance of reed beds are costing money. This is why a fourth function of the reed has been added: utilisation as energy crop for heat supply.
Experimental oven
Scientists are testing the system on some 5 hectares, of which 3.5 hectare reed, on the Lankheet Estate in Overijssel. Via an experimental oven this reed is intended to supply heat to an adjacent building. This testing is done in close cooperation with the Rijn and IJssel Waterboard. Because the current reed acreage is too small to supply all heat, grass clippings from road verges are added. The total amount is about thousand tonnes of dry biomass per year.
A provisional computer model can calculate the reed bed area required for purification of a catchment area to meet the criteria of the Water Framework Directive. The 20 000 hectares of the catchment area of the Buurserbeek, which passes the Lankheet Estate, require 300 to 400 hectare of reed beds.
The Waterboard is content with these results. The income from the heat supply is still too low to make the system cost-effective. The researchers are therefore – together with the consortium partners – investigating new financial constructions for this new form of land use.
Cooperation
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