Carbon capture and utilization (CCU) to produce methanol is a beneficial pathway to use carbon dioxide (CO₂) and mitigate climate change. Existing life cycle assessments demonstrate that CCU methanol generates a net CO₂ benefit when the hydrogen (H₂), required for hydrogenating the captured CO₂, is generated by electrolyzing water using renewable electricity (RE). However, the findings do not account for the environmental opportunity cost when RE can be supplied to the grid to offset CO₂ intensive electricity instead of electrolyzing water, the energy penalty of capturing CO₂ and the scope for technological improvement. This study quantifies the environmental opportunity cost and determines the net CO₂ emissions when CCU methanol offsets the production of conventional methanol across 14 scenarios. The 14 scenarios account for capturing CO₂ from 3 sources (combined and conventional natural gas, and coal power plants) and generating H₂ with electricity from 3 sources (photovoltaics, wind and the grid). The CO₂ avoided by using RE on the grid is greater than that from producing CCU methanol by 660 to 11960 kg CO₂/ton methanol across the 14 scenarios. Unless the grid CO₂ intensity drops below 67 g CO₂/kWh, it is environmentally preferable to supply RE to the grid than for use in CCU methanol production. At the thermodynamic limit of CCU methanol production, the grid CO₂ intensity should be lower than 82 g CO₂/kWh, which is unlikely in the US before 2050.

碳捕获和利用（CCU）生产甲醇是利用二氧化碳（CO ₂）和缓解气候变化的有益途径。现有的生命周期评估表明，当通过使用可再生电力（RE）电解水生成氢化捕获的CO ₂所需的氢（H ₂）时，CCU甲醇会产生CO ₂净收益。但是，当可以将RE提供给电网以抵消CO ₂密集的电力而不是电解水时，该发现并未考虑环境机会成本，这是捕获CO ₂的能量损失。以及技术改进的范围。这项研究量化了环境机会成本，并确定了CCU甲醇抵消了14种情况下常规甲醇的生产时的净CO ₂排放量。这14种情况说明了如何从3种来源（混合天然气和常规天然气以及燃煤发电厂）捕获CO ₂，并用3种来源（光伏，风能和电网）的电产生H ₂。在这14种情况下，通过在电网上使用RE避免的CO ₂大于产生CCU甲醇的660至11960 kg CO ₂ /吨甲醇。除非栅格CO ₂强度降至67 g CO _2以下/ kWh，向环境中供应可再生能源比在CCU甲醇生产中使用更可取。在CCU甲醇生产的热力学极限下，电网CO ₂强度应低于82 g CO ₂ / kWh，这在美国到2050年之前是不可能的。