Abstract
Rising global energy needs and limited fossil fuel reserves have led to increased use of renewable energies. In Germany, this has entailed massive exploitation of agricultural biomass for biogas generation, associated with unsustainable farming practices. Organic agriculture not only reduces negative environmental impacts, organic farmers were also prime movers in anaerobic digestion (AD) in Germany. This study’s aim was to identify the structure, development, and characteristics of biogas production associated with organic farming systems in order to estimate further development, as well as energetic and associated agronomic potentials. Surveys were conducted among organic farms with AD technology. 144 biogas plants could be included in the analysis. Total installed electrical capacity was 30.8 MWel, accounting for only 0.8% of the total installed electrical capacity in the German biogas sector. Recently, larger plant types (>250 kWel) with increased use of (also purchased) energy crops have emerged. Farmers noticed increases in yields (22% on average) and quality of cash crops in arable farming through integrated biogas production. In conclusion, although the share of AD in organic farming is relatively small it can provide various complementary socio-ecological benefits such as the enhancement of food output through digestate fertilization without additional need for land, while simultaneously reducing greenhouse gas emissions from livestock manures and soils. However, to achieve this eco-functional intensification, AD systems and their management have to be well adapted to farm size and production focus and based primarily on residue biomass.
Highlights
Growing global energy needs and increasing efforts to substitute fossil fuels have led to extensive production of agricultural biomass for purposes of renewable energy generation [1]
Important, according to farmers’ statements, were considerations of nutrient management and expected advantages of digestate fertilization (90%). 85% of the respondents stated that their on-farm need for thermal energy and a purposeful utilization of excess heat from biogas combustion was an important reason to invest in biogas production
As biogas was developed on, and integrated into, organic farms in order to attain the goal of a preferably independent farming system by a few dedicated pioneers, today, despite of its rapid growth rates it still plays a rather subordinate role regarding the share of renewable energy provision
Summary
Growing global energy needs and increasing efforts to substitute fossil fuels have led to extensive production of agricultural biomass for purposes of renewable energy generation [1]. Large-scale industrialized farming, in general, and intensive energy crop production, in particular, are increasingly drawing criticism from various stakeholders for their negative external effects [4,5,6]. Organic farming systems (OFS) alleviate the environmental burden of agricultural production by minimizing negative externalities and generating ecological benefits [7,8,9]. Organic agriculture is frequently challenged for its lower productivity in terms of output per unit of land [10]. With increasing biomass demands for food, fodder, material, and energy the pressure on ecosystems and natural resources is further increasing [11], and an intensification through external input use appears inevitable to boost agricultural productivity
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