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 MW_el, accounting for only 0.8% of the total installed electrical capacity in the German biogas sector. Recently, larger plant types (>250 kW_el) 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.

Many agronomic studies have shown the advantages of species mixtures (SM), but for food grain production, they represent only a small niche. Empirical studies that investigate reasons for SM adoption in food grain production are scarce. Here we present an in-depth study based on qualitative expert interviews with nine farmers. By means of interpretative analysis and reconstruction, socially shared models of SM adoption were built to identify the five main factors for SM adoption: (1) perceived relative mixture performance compared to sole crops, (2) suitability within the farm context (3), challenges and opportunities in mixture management due to increased complexity, (4) knowledge and technology as resources to handle mixture management and (5) quality standards in the food value chain. Relative performance was perceived as higher for SM than for sole crops for crop protection, nutrient efficiency, farm diversification, total yield stability and grain quality. The yield stability of individual crop species in SM was perceived as lower and grain impurities higher, requiring increased separation efforts. The economic potential of SM was perceived as highly variable, depending on crop value and post-harvest efforts to attain food quality. Reconstructing the mixture management process revealed that the interspecific plant interactions and emergent mixture attributes increased the cropping system complexity and affected the entire farming process. Adopting SM required knowledge about species interactions, mixture attributes and equipment settings. Large knowledge gaps for food SM were identified. The complexity of SM also provided opportunities for farmers to design mixtures that allow competition control (alternate rows) or avoid separation (relay mixtures). The main conclusions are: (1) increased complexity is a basic property of SM compared to sole crops, enabling advantages and increasing the option space to develop new sustainable cropping systems, (2) specific knowledge and technology are required for SM and are not accessible for most farmers, requiring new information channels and (3) new food SM should be developed more systematically, taking into account mixture properties and their effects on the farming process, as well as needs from the food value chain.