Life-cycle assessment of biogas production under the environmental conditions of northern Germany: greenhouse gas balance

Abstract

A considerable expansion of biogas production in Germany, paralleled by a strong increase in maize acreage, has caused growing concern that greenhouse gas (GHG) emissions during crop substrate production might counteract the GHG emission saving potential. Based on a 2-year field trial, a GHG balance was conducted to evaluate the mitigation potential of regionally adapted cropping systems (continuous maize, maize-wheat-Italian ryegrass, perennial ryegrass ley), depending on nitrogen (N) level and N type. Considering the whole production chain, all cropping systems investigated contributed to the mitigation of GHG emissions (6·7-13·3 t CO 2 eq/ha), with continuous maize revealing a carbon dioxide (CO 2 ) saving potential of 55-61% compared with a fossil energy mix reference system. The current sustainability thresholds in terms of CO 2 savings set by the EU Renewable Energy Directive could be met by all cropping systems (48-76%). Emissions from crop production had the largest impact on the mitigation effect (5 50%) unless the biogas residue storage was not covered. The comparison of N fertilizer types showed less pronounced differences in GHG mitigation potential, whereas considerable site effects were observed.

Density of Biogas Power Plants as An Indicator of Bioenergy Generated Transformation of Agricultural Landscapes

“…The intensive use of biogas power plants in this area is offering a profitable additional or alternative income to farmers, compared to other common local land-use practices like permanent pasture for dairy farming fodder production. In addition, biogas power plants provide opportunities to process manure, which is available in large amounts in regions of high cattle density [10,14,22,23,65].…”

“…Laggner et al [14] noted an increase in silage maize area in most communities where pastureland area decreased between 1999 and 2007. Conversion of permanent pasture to grow crops like silage maize is related to increasing risks of soil erosion and compaction [19,20], increasing nitrogen mineralization and leaching [21][22][23], increasing release of greenhouse gases from humus degradation [22] and changes in local bio-diversity [16,18,22]. In addition, the traffic in the proximity to biogas power plants usually increases seasonally due to the large amount of feedstock material transported from the surrounding fields to the power plant site in harvesting time [24].…”

Integrating power-to-gas in the biogas value chain: analysis of stakeholder perception and risk governance requirements

“…Such land use transformation has been associated with significant detrimental environmental effects, including more considerable vulnerability to soil erosion from the wind as well as soil compaction due to the use of heavy machines [40,41]. This land-use change also causes larger organic matter mineralization and leaching of nitrogen [42][43][44], increased emissions of carbon dioxide and nitrogen from the degradation of organic matter [43], and adverse alterations in regional biodiversity [45,46]. Moreover, conflicts of interest exist between maize cultivation for biogas and other agronomic markets.…”

“…We interpreted the findings in the light of the cultural theory of risk (CT) [40][41][42][43][44][45] which understands risk perception as a socially predetermined selection by which "individuals choose what to fear (and how much to fear it), in order to support their "way of life"" [73]. With a focus on collective, social, and group-specific conventions that influence individual risk perception, CT sheds light on the filters that influence the opinions of laypersons and experts on the risks, acceptance, and legitimacy of biogas and the implementation of PtG.…”

Evaluating Bioenergy Cropping Systems towards Productivity and Resource Use Efficiencies: An Analysis Based on Field Experiments and Simulation Modelling

“…Thereby, the experimental data were analyzed by a simulation model taking sequently measured crop variables as input. In other studies based on the same field experiments, aspects of different N sources including biogas residues on productivity [15,16], N losses due to leaching [17], NH 3 volatilization [18], N 2 O emissions [19], and their effects on a life cycle assessment (LCA) analysis [20] have already been given.…”