Synthetic natural gas as a green hydrogen carrier – Technical, economic and environmental assessment of several supply chain concepts
Fabian Carels, Lucas Sens, Martin Kaltschmitt
Abstract
• The assessed concepts enable hydrogen supply based on synthetic natural gas. • Electrified steam methane reforming reduces energy input over autothermal reforming. • Closed CO 2 cycles allow energy and cost savings over supply via direct air capture. • For a distance of 10,000 km, CO 2 cycling can be realized at around 60 € 2020 /t CO2. • Costs of hydrogen supply are estimated at 6.6 to 8.6 € 2020 /kg H2 for 2030. Based on synthetic natural gas, existing natural gas markets and infrastructures can be used to make renewable sources of energy from sun- and/or wind-rich regions available on a global scale. To overcome the challenge of providing non-fossil CO 2 for the production of this synthetic natural gas, a novel concept analyzed in this paper envisages to reform the synthetic natural gas in the importing country and transporting the captured CO 2 back to the exporting country to be reused for the production of synthetic natural gas; i.e., the synthetic natural gas serves as a hydrogen carrier. This paper examines and compares the energy efficiency, cost and greenhouse gas emissions of different hydrogen supply chains using synthetic natural gas as a carrier related to the year 2030. To do so, all relevant components are taken into account to model the entire supply chains. A special focus is put on different options for providing the required CO 2 and on different technologies for synthetic natural gas reforming. The assessment shows that the availability of a cheap source of biogenic CO 2 at the point-of-export as well as electrified steam methane reforming result in the lowest hydrogen supply cost of 6.6 to 7.0 € 2020 /kg H2 , also achieving best results in terms of energy efficiency (around 44%). With regard to minimizing greenhouse gas emissions, autothermal reforming of methane appears to be advantageous. A closed CO 2 cycle is favorable over sole onsite CO 2 provision, if no cheap CO 2 of non-fossil origin is available at the point-of-export and the costly direct air capture process would have to be used.