Biogas production from submerged macrophytes—a case study of regional biomass potentials in Germany

• Main Authors: Markus Röhl, Sandra Roth, Wolfgang Schütz, Andreas Zehnsdorf, Carsten Herbes
• Format: Article
• Language: English
• Published: BMC 2019-06-01
• Series: Energy, Sustainability and Society
• Subjects: Aquatic macrophytes; Aquatic biomass; Biomass potential; Alternative substrates for biogas production; Water body management and maintenance; Aquatic de-weeding operations
• Online Access: http://link.springer.com/article/10.1186/s13705-019-0204-5

Abstract Background Utilization of energy crops for biogas production has been controversially discussed in Germany due to negative environmental effects and the “food vs. fuel” debate. This led to a search for alternative substrates focusing on material from landscape management measures. Aquatic biomass is harvested during water body management, yet it has not been considered for energy generation. Methods The information where and which amount of biomass is collected by aquatic de-weeding operations in rivers and lakes was gathered via a nationwide survey. In addition to that, the amount of aquatic plant biomass potentially available in water bodies was estimated exemplarily for the flowing waters of Baden-Württemberg—by using data from the European Water Framework Directive surveys. Results The survey revealed 172 locations of de-weeding operations in flowing waters and 93 in standing waters. These locations are concentrated in lowland rivers of the North German Plain as well as the Upper Rhine Plain. Standing water de-weeding operations were reported mainly from the foothills of the Alps. The overall amount of biomass harvested per year is 36,244 t of fresh biomass. Taking into account missing data, a maximum of 100,000 t of fresh biomass per year can be estimated for Germany. The case study on plant biomass de-weeded from waters in Germany revealed that only a small part of the total aquatic plant biomass is actually harvested. Conclusions The amount of biomass harvested and removed from water bodies in Germany is considerably lower than the harvest of other substrates from landscape management measures such as mowing of meadows or trimming of trees and hedges. However, larger amounts are accumulating locally, concentrated in some regions or at specific water bodies, e.g., reservoirs, for which regional value chains could be established. In order to make the exploitation of these local potentials economically viable, changes regarding the economic and technological framework are required.