Auswirkungen der Einbindung einer Biogasanlage in ein ökologisches Betriebssystem

Summary

Biogas plants gain increasing circulation in organic agriculture. Among systems engi-neering effects on matter cycles, soil, plants and environment particularly depend on the integration of the biogas plant into the farming system. Ecological effects should already be taken into consideration in the planning stage. Therefore appropriate tools are required.
In this contribution ecological effects of changing an organic cash crop farming system into a biogas system are shown by using an established modelling approach. Starting from an existing cash crop farm a biogas-scenario was developed which includes e. g. structural adaptations of the cultivation system and crop rotation, the use of internal products and manuring. The biogas plant was conceived as a joint plant so that matter flows between the examined farming system and neighbouring farms occur. Scenario calculations show that the integration of a biogas plant with a capacity of 350 kWel on a 250 ha cash crop farm leads to intensified nitrogen flows by what yield potentials but also potential nitrogen losses increase. Energy input as well as energy tie-up in crop production rise. Energy efficiency (output/input-relation) is highly dependent on the chosen energy crop. Planning energy crop rotations risks of soil erosion and minimiz-ing strategies need to be taken into consideration. Plant capacities are to be com-pared with biomass yields. Yield potentials of energy crops have to be realistically estimated in consideration of ecological aspects to avoid incorrect planning.