Rushes are prominent wetland plants that are well adapted to conditions of waterlogging. Tall rushes like soft rush (Juncus effusus L.) tend to dominate the vegetation and offer a great biomass potential. Removing rush biomass is often necessary to enhance various ecosystem services of wetlands. There is an urgent need for sustainable use of the removed biomass apart from expensive composting ore useless landfill. We investigated three alternative energy utilisation routes for soft rush biomass and evaluated their energetic potential: biomethanisation via wet fermentation technique (a), biomethanisation via solid-state fermentation technique (b) and combustion (c). Batch experiments (a), experimental fermenters (b), and thermo-calorimetric equipment (c) were used to measure energy output per unit rush biomass input. The wet fermentation technique had significantly higher biogas yields than solid-state fermentation (399 LN kg−1 oDM compared to 258 LN kg−1 oDM). These yields constitute 59 and 43%, respectively, of the biogas potential of maize silage as a reference. Solid-state fermentation technique needs longer retention time compared to wet co-digestion to earn comparable methane yields. Soft rush biomass shows high heating values (15.06 MJ kg FMw15−1) compared to other herbaceous solid fuels. Low costs for substrate production make energetic utilisation of Juncus effusus an interesting alternative, if short distances between fields and biomass conversion plant can be realised. All investigated conversion routes appear promising, provided that the substrate specifics are considered in the design of the conversion technique. Besides the size of the rush dominated area and the distribution of these areas in the landscape, the investment costs and the subsidies for the conversion plant play a pivotal role in the selection of the preferred conversion path.

中文翻译：

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不同转化途径下软草（Juncus effusus L.）的能量势

灌木丛是重要的湿地植物，非常适合涝灾。像软草丛（Juncus effusus L.）一样的高草丛往往占主导地位，并提供了巨大的生物量潜力。通常必须去除仓促的生物量，以增强湿地的各种生态系统服务。除了昂贵的堆肥矿石或无用的垃圾填埋场外，迫切需要可持续利用去除的生物质。我们研究了软草生物质的三种替代能源利用途径，并评估了它们的能量潜力：通过湿发酵技术进行生物甲烷化（a），通过固态发酵技术进行生物甲烷化（b）和燃烧（c）。分批实验（a），实验发酵罐（b）和热热分析设备（c）用于测量单位高峰生物量输入的能量输出。湿发酵技术比固态发酵具有更高的沼气产量（399 LN kg-1 oDM与258 LN kg-1 oDM）。这些产量分别占玉米青贮饲料沼气潜力的59％和43％。与湿法共消化相比，固态发酵技术需要更长的保留时间才能获得可比的甲烷收率。与其他草本固体燃料相比，轻度急流生物质显示出较高的发热量（15.06 MJ kg FMw15-1）。如果可以实现田间和生物质转化工厂之间的短距离，则底物生产的低成本使对Juncus effusus的能源利用成为一种有趣的选择。只要在转化技术的设计中考虑了底物的特性，所有研究的转化途径都有望实现。