As part of the Green Deal, greenhouse gas emissions in the EU are to be reduced by at least 55% by 2030 compared to 1990 levels. The Renewable Gas Act is proposed in Austria as a key contribution to achieving these targets. By 2030, 9.75% or at least 7.5 TWh of fossil natural gas is to be replaced annually by nationally produced renewable gas - in comparison, consumption in 2022 was around 85 TWh. From 2024, annually increasing green gas quotas are to be implemented, which must be guaranteed by the suppliers - in the event of non-compliance, €150/MWh must be paid.

Gasification in the dual fluidized bed (DFB) is a state-of-the-art process for converting woody biomass into product gas and using it to generate electricity and heat. The product gas from DFB gasification is considered very suitable for the production of synthetic natural gas (SNG) due to the comparatively high H2/CO ratio, the high CH4 content and the absence of N2 dilution. Projects for SNG production from woody biomass in Güssing, AT (1 MWSNG), Gothenburg, SE (20 MWSNG) and Lyon, FR (500 kWSNG) have demonstrated the technical feasibility.

Despite this, the technology has not yet been successfully implemented. The biggest issues to be resolved in the I/O-Gas project are divided into sub-processes:

1. Gasification: The use of biogenic residues with low ash-melting temperatures and high volatile content and the long-term behavior on downstream process steps with regard to deposits of tar and inorganic components has not been sufficiently researched. Suitable pre-treatment processes and specific concepts for feedstocks with high moisture content as well as seasonal and decentralized biomass are lacking.

2. Gas cleaning: For the use of biogenic residues, it is unclear which concentrations of impurities are to be separated and how compounds with relevance to the composition of biogenic residues (e.g. halides) are separated with gas cleaning to date. It is also unclear how the existing chain can deal with the often-higher concentrations of certain impurities. Significant increases in efficiency also possible and necessery during the regeneration of these gas purification stages.

3. SNG production: The methanation (multi-stage adiabatic fixed-bed cascade) and upgrading technologies (especially CO2 capture) used in refinery technology are too complex and cost-intensive for the operation of comparatively small biomass plants. The potential for increasing the energy efficiencies through suitable integration into the energy sector is very high.

By coupling gas generation with pre-treatment processes such as hydrothermal carbonization or pyrolysis, the fuel potential can also be extended to low-melting and moist biogenic residues. The use of straw-like biomass alone in DFB gas production could lead to an increase in SNG production of around 11 TWh/a in Austria – other input materials are possible. Through suitable sector coupling with the energy system using e.g. electrolysis-H2, the carbon utilization rate can be roughly doubled compared to the current state of the art. The SNG product generation costs can be significantly reduced with the proposed solutions and, according to the current state of knowledge, are then less than half of the proposed penalty payments of €150/MWh.