* Corresponding author: Daniel C. Rosenfeld email: rosenfeld@energieinstitut-linz.at Detritus / Volume 16 - 2021 / pages 106-120 https://doi.org/10.31025/2611-4135/2021.15121 © 2021 Cisa Publisher. Open access article under CC BY-NC-ND license POTENTIALS AND COSTS OF VARIOUS RENEWABLE GASES: A CASE STUDY FOR THE AUSTRIAN ENERGY SYSTEM BY 2050 Daniel C. Rosenfeld *, Johannes Lindorfer, Hans Böhm, Andreas Zauner and Karin Fazeni-Fraisl Energieinstitut an der Johannes Kepler Universität Linz, Altenberger Straße 69, 4040 Linz, Austria Article Info: Received: 24 March 2021 Revised: 3 August 2021 Accepted: 23 August 2021 Available online: 30 September 2021 Keywords: Anaerobic digestion Power-to-gas Gas greening Biomass gasifcation Technoeconomic analysis ABSTRACT This analysis estimates the technically available potentials of renewable gases from anaerobic conversion and biomass gasifcation of organic waste materials, as well as power-to-gas (H2 and synthetic natural gas based on renewable electricity) for Austria, as well as their approximate energy production costs. Furthermore, it outlines a theoretical expansion scenario for plant erection aimed at fully using all technical potentials by 2050. The overall result, illustrated as a theoretical merit or- der, is a ranking of technologies and resources by their potential and cost, starting with the least expensive and ending with the most expensive. The fndings point to a renewable methane potential of about 58 TWh per year by 2050. The highest po- tential originates from biomass gasifcation (~49 TWh per year), while anaerobic digestion (~6 TWh per year) and the power-to-gas of green CO2 from biogas upgrad- ing (~3 TWh per year) demonstrate a much lower technical potential. To fully use these potentials, 870 biomass gasifcation plants, 259 anaerobic digesters, and 163 power-to-gas plants to be built by 2050 in the full expansion scenario. From the cost perspective, all technologies are expected to experience decreasing specifc energy costs in the expansion scenario. This cost decrease is not signifcant for biomass gasifcation, at only about 0.1 €-cent/kWh, resulting in a cost range between 10.7 and 9.0 €-cent/kWh depending on the year and fuel. However, for anaerobic digestion, the cost decrease is signifcant, with a reduction from 7.9 to 5.6 €-cent/kWh. It is even more signifcant for power-to-gas, with a reduction from 10.8 to 5.1 €-cent/kWh between 2030 and 2050. 1. INTRODUCTION The major challenge of this century is climate change. To tackle this challenge, it is necessary to fnd measures to limit the temperature rise to a maximum of 2°C, or even 1.5°C in an optimal case (Gao et al., 2017). Therefore, it is necessary to signifcantly reduce global CO 2 emissions and reach, at a minimum, carbon neutrality within the next 20 to 30 years. On a European scale, in 2011, the European Union pub- lished a “roadmap for moving to a competitive low-carbon economy in 2050.” This roadmap aims for a greenhouse gas emission reduction of 80% to 95% by 2050 (European Commission, 2011). In 2019, the European Union published “new green deal” priority energy effciency measures. How- ever, these measures further include the substitution of 72% of current fossil-based energy by renewable energy since this amount cannot be reduced by effciency meas- ures (European Commission, 2019). This goal could be reached by either electrifcation using renewable electricity or substitution with a renewable alternative such as fossil natural gas with synthetic natural gas (SNG). This action plans to reach net carbon neutrality by 2050 are mainly be- ing carried out on a national basis. The objective of the current program of the Austrian Federal Government is to provide 100% of Austria's elec- tricity supply from renewable energy sources by 2030. Doing so requires an increase in renewable electricity gen- eration of 27 TWh in total (11 TWh photovoltaic, 10 TWh wind power, 5 TWh hydropower, and 1 TWh biomass). Re- garding gas supply, an expansion and support program is planned to promote the production of renewable gas (i.e., biomethane, green hydrogen, and SNG based on renewable electricity) by 2030. The aim is to feed 5 TWh of "green gas" into the natural gas grid by 2030. A full decarbonization of the Austrian economy, aiming for carbon neutrality, should be reached by 2040 (Republik Österreich, 2020). Therefore, the Austrian natural gas demand – 87.2 TWh in 2018 (Brit- ish Petroleum p.l.c, 2019) – must be reduced and fully sub- stituted by renewables.