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. 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. 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. 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.

中文翻译：

---

沉水植物的沼气生产-以德国区域生物质潜力为例

由于负面的环境影响和“粮食与燃料”的争论，德国已经讨论了将能源作物用于沼气生产的问题。这导致寻找替代衬底，重点是景观管理措施中的材料。水生物质是在水体管理过程中收获的，但尚未考虑用于能源生产。通过一项全国性调查收集了河流和湖泊中的水草除草作业收集的生物量和收集量的信息。除此之外，还使用欧洲水框架指令调查中的数据，对巴登-符腾堡州的流水示例性地估算了水体中潜在可用的水生植物生物量。调查显示，在流水中有172个除草作业地点，在死水中有93个除草作业地点。这些位置集中在北德平原和莱茵河上游的低地河流中。据报死水除草操作主要在阿尔卑斯山的山脚下进行。每年收获的生物质总量为36,244吨新鲜生物质。考虑到缺失的数据，德国每年最多可估计100,000吨新鲜生物质。对德国从水中除草的植物生物量进行的案例研究表明，实际上仅收获了水生植物总生物量的一小部分。在德国，从水体中采集和清除的生物量要大大低于通过景观管理措施（例如割草或修剪树木和绿篱）获得的其他基质。但是，更多的是在当地积累，集中在某些地区或特定的水体，例如水库，为此可以建立区域价值链。为了使这些当地潜力的开发在经济上可行，需要改变经济和技术框架。