Methane has enormous potential as a carrier for renewable H₂. The required infrastructure for a methane gas economy is readily available, and it can compete with its energy-intensive liquefied hydrogen (LH₂) counterpart. In this work, we conducted a technoeconomic analysis of the production of liquefied synthetic methane (LSM) from ambient CO₂ and renewable H₂. The process entails (1) capture of CO₂ directly from ambient air, referred to as Direct Air Capture (DAC) using an amine-based system; (2) generation of H₂ from renewable sources, (3) conversion of CO₂ and H₂ to synthetic methane; and (4) liquefaction of synthetic methane. The technoeconomic model used in this study is based on mass/material energy flow analysis and includes the economics of all processes involved.

Building on our previous work, we reduced the overall capture cost for the studied scale of 0.291 t/h CO₂ production from US$557 to ~$365/tCO₂. At a scale equivalent to 1 MtCO₂/year capture, which is the basis for production of LSM in this work, we estimated the cost of DAC to be ~$114/tCO₂. Per GJ of methane produced, the overall cost of LSM was ~$31.5/GJ, comprising around $21.7/GJ ($2.4/kg H₂) for hydrogen production, $5.6/GJ for DAC, $1.4/GJ for methanation and $2.8/GJ for methane liquefaction. The energy conversion efficiency of LSM was lower than for LH₂, mainly due to the large amount of heat required for DAC. The levelised cost per unit of energy for LSM was lower at small scales, while the costs were the same (~$32/GJ) at a larger scale of 180 kt/year hydrogen production. Our detailed analysis provides insights into the suitability of LSM as a carbon-neutral fuel that can compete economically with LH₂.

甲烷作为可再生 H ₂的载体具有巨大的潜力。甲烷气体经济所需的基础设施很容易获得，并且可以与能源密集型液化氢 (LH ₂ ) 对应物竞争。在这项工作中，我们对从环境 CO ₂和可再生 H ₂生产液化合成甲烷 (LSM) 进行了技术经济分析。该过程需要 (1)直接从环境空气中捕获 CO ₂，称为使用基于胺的系统的直接空气捕获 (DAC)；(2)从可再生能源产生 H ₂，(3) CO ₂和 H _{2 的}转化合成甲烷；(4)合成甲烷的液化。本研究中使用的技术经济模型基于质量/材料能量流分析，包括所有相关过程的经济性。

在我们之前的工作的基础上，我们将所研究的 0.291 t/h CO ₂生产规模的总捕集成本从 557 美元降低到约 365 美元/tCO ₂。在相当于 1 MtCO ₂ /年捕获量的规模下，这是本工作中 LSM 生产的基础，我们估计 DAC 的成本约为 $114/tCO ₂。每 GJ 产生的甲烷，LSM 的总成本约为 31.5 美元/GJ，其中包括约 21.7 美元/GJ（2.4 美元/kg H ₂）的制氢、5.6 美元/GJ 的 DAC、1.4 美元/GJ 的甲烷化和 2.8 美元/GJ 的甲烷液化。LSM 的能量转换效率低于 LH ₂，主要是因为DAC需要大量的热量。LSM 的每单位能源平准化成本在小规模下较低，而在 180 kt/年制氢的较大规模下成本相同（~32 美元/GJ）。我们的详细分析提供了关于 LSM 作为碳中和燃料的适用性的见解，可以在经济上与 LH ₂竞争。