Using renewable hydrogen in direct methanation

Cosyma
Cosyma test container, © Energie 360°

Until 2030, Switzerland’s heat generation from renewable gas is to increase from today’s roughly 1 percent to 30 percent. To achieve greater efficiency in the use of raw gas sources, Zurich-based energy supplier Energie 360° and the PSI – Paul Scherrer Institute have been working on developing a new power-to-gas technology. Together, they created a prototype, put through a long-term test cycle in the lab, that meets the requirements for unrestricted pipeline supply and produces 60 percent more renewable gas from sewage and solid waste treatment. The findings mark an important milestone in meeting the 2030 target.

Despite major growth in domestic biogas production over the past decade, non-imports add up to only around 1 percent today. Increasing Switzerland’s biogas share to 30 percent in slightly more than a decade will be a challenging task. Energie 360° and the PSI have now brought the country one step closer to its renewable goals by devising a system that makes use of the 40 percent of carbon dioxide contained in raw biogas and released through sewage and solid waste treatment. Conventional plants will remove this carbon dioxide from the biogas before injecting the remainder, 60 percent of almost pure methane, into the national pipeline system. If, however, hydrogen were added, the mixture could be put through a power-to-gas cycle and lead to a 60 percent increase in methane output.

If all the existing Swiss sewage and solid waste treatment plants that produce biogas close to a pipeline received a power-to-gas upgrade, today’s renewable gas total in the national transmission system could be increased to 1,400 gigawatt-hours. In 2016, output was at 308 gigawatt-hours per year. Thus, the retrofit would make it possible to store more than 900 gigawatt-hours of electricity in the network.

Nearly 100 potential power-to-gas sites can be found across the country. The majority, 64 to be exact, are at sewage treatment plants. Most of these plants do not yet possess any injection station but use CHP technology to generate power and heat from sewage gas. CHP may be suitable for this purpose, but there are more effective and efficient processes that would likewise provide greater environmental benefits.

Economic feasibility

Biogas is an eco-friendly alternative to natural gas, but its cost of production is higher. The difference is not a concern to customers, who are willing to pay more to protect the environment. Biogas is also exempt from fuel taxes and carbon fees, which has made it possible to operate conventional waste-to-energy plants without the need for public funding. This is the kind of milestone that power-to-gas should be able to reach. The aim of our feasibility analysis was to determine whether power-to-gas systems could achieve economically sustainable operation at similar or lower capital and operating costs per kilowatt-hour of gas produced.

The exemption from taxes and fees was changed in 2016 to include methane sourced from renewable hydrogen, provided that the carbon dioxide produced during the process was not used specifically for methanation. As a result, syngas is now competing on an equal footing with today’s biogas. Thus, we assumed that it will eventually achieve the same price levels as the latter does on today’s market.

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On Jan. 11, 2018, at the New Year’s event of Switzerland’s federal energy ministry BFE in Bern, the Cosyma project was recognized with the Watt d’Or award in the Renewable Energy category.

Written by:

Andreas Kunz, Energie 360°, Zurich, Switzerland

Julia Witte, Serge Biollaz, Tilman Schildhauer, all for Paul Scherrer Institute, Villigen, Switzerland

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