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 CO2 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 CO2 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 CO2 and on different technologies for synthetic natural gas reforming. The assessment shows that the availability of a cheap source of biogenic CO2 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/kgH2, 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 CO2 cycle is favorable over sole onsite CO2 provision, if no cheap CO2 of non-fossil origin is available at the point-of-export and the costly direct air capture process would have to be used.

中文翻译：

---

合成天然气作为绿色氢载体 – 对多个供应链概念进行技术、经济和环境评估


基于合成天然气，现有的天然气市场和基础设施可用于在全球范围内提供来自太阳能和/或风能丰富地区的可再生能源。为了克服为这种合成天然气生产提供非化石 CO2 的挑战，本文分析的一个新概念设想在进口国改革合成天然气，并将捕获的 CO2 运回出口国，重新用于合成天然气的生产;即，合成天然气用作氢载体。本文检查和比较了与 2030 年相关的使用合成天然气作为载体的不同氢供应链的能源效率、成本和温室气体排放。为此，将所有相关组件考虑在内，以对整个供应链进行建模。特别关注提供所需 CO2 的不同选择和合成天然气重整的不同技术。评估表明，在出口点提供廉价的生物 CO2 来源以及电气化蒸汽甲烷重整，可实现最低的氢气供应成本，为 6.6 至 7.0 欧元/kgH2，在能源效率方面也取得了最佳结果（约 44%）。在最大限度地减少温室气体排放方面，甲烷的自热重整似乎是有利的。如果出口点没有廉价的非化石来源的 CO2，并且必须使用昂贵的直接空气捕获过程，那么封闭的 CO2 循环比单独的现场 CO2 供应更有利。