Abstract
We conducted the Life Cycle Analysis (LCA) of energy production from biogas for maize and three types of wetland biomass: reed Phragmites australis, sedges Carex elata, and Carex gracilis, and “grassy vegetation” of wet meadows (WM). Biogas energy produced from maize reached over 90 GJ ha−1, 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−1). The greenhouse gases (GHG) emissions released during preparation of the feedstock and operation of the biogas plant were 150 g CO2 eq. kWhel.−1 for DF of sedges and 262 g CO2 eq. kWhel.−1 for WF of Phragmites. 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 CO2 eq. kWhel.−1 for DF of Phragmites and 2738 g CO2 eq. kWhel.−1 for the WM and, in most cases, exceeded those related to fossil fuel technologies.
Highlights
Biomass presents an energy source that can be stored and converted into electricity and gas fuels in both solid and liquid forms
Compared to the prevailing coal-based power generation in Central Europe, anaerobic digestion (AD) of wetland biomass could contribute to a reduction in greenhouse gases (GHG) emissions by 74% to 85%
Our results indicate that wetland biomass can provide a promising alternative pathway for sustainable biogas generation
Summary
Biomass presents an energy source that can be stored and converted into electricity and gas fuels in both solid and liquid forms. In the European Union (EU) and worldwide, the bioenergy sector is growing substantially due to a broad spectrum of biomass applications, despite the tremendous development of solar and wind technologies, biomass remains the primary source of renewable energy. In 2016, bioenergy derived from a range of feedstocks contributed 116 Mtoe to the EU’s gross final energy consumption, with heating and cooling sectors consuming about 75% of all bioenergy produced. Forestry delivered more than 60% of all EU biomass for energy purposes, while 27% of biomass (36 Mtoe) originated from crops and agricultural by-products [1]. The availability of resources varies regionally: e.g., forest biomass was the most important feedstock for renewable energy in Scandinavia [2], while, in the UK, the highest bioenergy potential was found for household wastes, energy crops, and agricultural residues [3]. The majority of agricultural biomass was utilized as a substrate for the anaerobic digestion (AD), making biodiesel and bioethanol
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