| Summary: | We conducted the Life Cycle Analysis (LCA) of energy production from biogas for maize and three types of wetland biomass: reed <i>Phragmites australis</i>, sedges <i>Carex elata,</i> and <i>Carex gracilis</i>, and “grassy vegetation” of wet meadows (WM). Biogas energy produced from maize reached over 90 GJ ha<sup>−1</sup>, which was more than four times higher than that gained from wetland biomass. However, an estimation of energy efficiency (EE) calculated as a ratio of energy input to the energy produced in a biogas plant showed that the wet fermentation (WF) of maize was similar to the values obtained for dry fermentation (DF) of sedge biomass (~0.30 GJ GJ<sup>−1</sup>). The greenhouse gases (GHG) emissions released during preparation of the feedstock and operation of the biogas plant were 150 g CO<sub>2</sub> eq. kWh<sub>el.</sub><sup>−1</sup> for DF of sedges and 262 g CO<sub>2</sub> eq. kWh<sub>el.</sub><sup>−1</sup> for WF of <i>Phragmites</i>. Compared to the prevailing coal-based power generation in Central Europe, anaerobic digestion (AD) of wetland biomass could contribute to a reduction in GHG emissions by 74% to 85%. However, calculations covering the GHG emissions during the entire process “from field to field” seem to disqualify AD of conservation biomass as valid low-GHG energy supply technology. Estimated emissions ranged between 795 g CO<sub>2</sub> eq. kWh<sub>el.</sub><sup>−1</sup> for DF of <i>Phragmites</i> and 2738 g CO<sub>2</sub> eq. kWh<sub>el.</sub><sup>−1</sup> for the WM and, in most cases, exceeded those related to fossil fuel technologies.
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