Biomass for bioenergy is an important option within global change mitigation policies. The present research focused on energy net production, net reduction of greenhouse gases (GHG) (considered as CO2-equivalents), and energy output:input ratio of the energy cropping systems 'rapeseed', 'maize', and 'Miscanthus'. The system-specific main products were biodiesel (rapeseed), electricity from biogas (maize), and Miscanthus chips (loose, chopped material); the related substituted fossil resources were diesel fuel (rapeseed), electricity from the German energy mix (maize), and heating oil (Miscanthus). However, research did not aim for a direct quantitative comparison of the crops. The study followed a case study approach with averaged data from commercial farms within an enclosed agricultural area (<5 km(2)) in Western Germany. Cultivation techniques were considered as communicated by farmers and operation managers; the diesel fuel consumption of agricultural machinery was modeled using an online-based calculator of the German Association for Technology and Structures in Agriculture (KTBL). Overall, rounded net energy production amounted to 66 GJ ha(-1) (rapeseed), 91 GJ ha(-1) (maize), and 254 GJ ha(-1) yr(-1) (Miscanthus); the related energy output:input ratios were 4.7 (rapeseed), 5.5 (maize), and 47.3 (Miscanthus), respectively. Compared to the respective fossil fuel-related energy supply, CO2-equivalent reduction potential ranged between 30 and 76% for electrical energy from maize biomass, 29 -82% for biodiesel from rapeseed, and 96-117% for Miscanthus chips, depending on whether or not the accruing by-products rapeseed cake, glycerin (rapeseed cropping system), and waste heat (maize) were considered. True 'CO2-neutrality' was only reached by the Miscanthus cropping system and was related to an additional credit from carbon sequestration in soil during the cultivation period; thus, this cropping system could be attributed to be a CO2-sink. The study indicated that bioenergy can be produced sustainably under commercial farming conditions in terms of a significantly reduced consumption of natural resources.
