The rediscovery of reed as a renewable resource
Even though an inventory of reed areas and their biomass is missing, it can be assumed that the total area of reed in the Baltic Sea’s shallow bays and coastal lagoons has increased substantially over the last decades covering by now at least 300,000 ha with potentially a total annual biomass of approx. 1 million tonnes available for use.
Reed has always been used as a source for various applications, but its qualities as a possible local renewable energy resource or an environmental remediation measure have so far not reached beyond the research community, and even experimental results are rare.
With an average calorific value of reed with moisture content of 20 % being 3.9 MWh/t and assuming that 15–20 % of the total aboveground biomass in the Baltic Sea could be used, its energy potential is no more than 4 TWh (compare: annual energy need of about 100,000 households).
But reed beds can also be considered as an effective method to remove excess nutrients from shallow coastal seas due to their high absorption potential for macronutrients, especially nitrogen. About 5,000– 10,000 tonnes of nitrogen and 500–1,000 tonnes of phosphorus could be eliminated from the coastal sea annually assuming that 100,000 ha (30 %) of the total reed bed area could be harvested (compare: 1 % of nitrogen and 3 % of annual phosphorous reductions of target levels set by the HELCOM Baltic Sea Action Plan).
The economic feasibility of innovative applications for reed shows large regional variations. In order to make it profitable costs need to be cut over the whole process chain and ecosystem service has to be included in the economic valuation. Especially harvesting technology has to be further developed not only in light of better economics, but also in view of environmental concerns (i.e. no damage of the ground).
Applications are also highly affected by differences of the chemical composition and physical properties of the reed depending on the season. Biogas production and nutrient removal can for instance only be done with summer reed. It is therefore highly important to find solutions which determine how much reed can be harvested at which time without negative effects on the natural ecosystem services which reed beds provide as an important habitat for nesting birds, fish and benthos.