Summary

For the generation of biomethane two conversion pathways are market mature respectively under development at the moment:

• the thermo-chemical biomass conversion (i.e. Bio-SNG),

• the bio-chemical biomass conversion (i.e. Biogas).

The conversion technologies for Bio-SNG and biogas differs significantly concerning e.g. the biomass feedstock, the conversion principle, the state of the technology, the installed capacity per conversion unit, the available technical experiences and the still given R&D demand. But both conversion routes allow the provision of biomethane fulfilling the requirements for a feed-in into the existing natural gas grid. Therefore biogas as well as bio-SNG has to be upgraded by different technical processes guaranteeing a similar calorific value and chemical composition compared to natural gas. Only if this prerequisite is fulfilled biomethane can be used in any mixture with natural gas by using the same infrastructure without creating possible problems at the end user.With regard to biogas production based on an anaerobic digestion the wet fermentation of biomass residues as well as energy crops (e.g. maize silage) are matured technologies. But so far the produced biogas (methane-rich gas) is used mainly in gas engines for power generation or for CHP. To allow for a feed-in into the natural gas network the quality of the currently used natural gas has to be achieved. The production of Bio-SNG is characterised by three main steps thermo-chemical gasification of lignocellulosic biomass (e.g. wood) to a synthesis gas (mainly CO and H₂), (ii) cleaning and conditioning of the synthesis gas fulfilling the requirements of following process steps and (iii) subsequent methanation of the synthesis gas into methane. The state of the technology of this conversion route is slightly behind the bio-chemical option. So far only the biomass gasification based on water vapour for the production of heat and electricity is market mature; one plant is operated since several years successfully in Güssing (in Austria) and other plants are in operation for few years (e. g. Oberwart in Austria) or are in their commissioning phase (e. g. Villach in Austria, Ulm in Germany). The subsequent methanation has been realised with a demonstration plant of 1 MW gas capacity in December 2008 in Güssing (in Austria). The situation with regard to the production of biomethane via bio- and thermo-chemical conversion route and the subsequent utilisation in the energy system differs strongly between the regarded countries. Furthermore, the activities in the field of implementing biomethane provision technologies are different between the single countries for instance in terms of the foreseen technologies, conversion plant scales as well as biomass supply structures.

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