Energy is required to convert CO₂ into useful products. Thermodynamic arguments can be made to show that, if the energy for the conversion of CO₂ is provided by combustion of fossil feedstock, it is not possible to consume more CO₂ than is produced. Renewable energy, specifically renewable power, is generally assumed to be the energy source for CO₂ utilization. Various options are available for using renewable power for mitigation of CO₂ emissions, including electroreduction of CO₂ to hydrocarbons, electrolysis of water to hydrogen, and power for battery electric vehicles. Thermodynamic and practical arguments can be used to rank the effectiveness of renewable power for CO₂ mitigation for these options, using power for light duty transportation as an example. Renewable power used to reduce water to hydrogen, which is then used to convert CO₂ into liquid fuels, is only one-fourth as effective at mitigating CO₂ emissions compared to use of the renewable power in a battery electric vehicle. The direct electroreduction of CO₂ to liquid fuels, even if achieved with 100% thermal efficiency, is only one-third as effective at mitigating CO₂ compared to the battery electric vehicle.

将CO ₂转化为有用的产品需要能量。可以进行热力学论证，以表明，如果通过燃烧化石原料提供用于转化CO ₂的能量，则消耗的CO ₂不可能比产生的更多。通常认为可再生能源，特别是可再生能源是利用CO ₂的能源。有多种选择可用于使用可再生能源来减少CO ₂排放，包括将CO ₂电还原为碳氢化合物，将水电解为氢以及电池电动车的电力。热力学和实践论据可用于对可再生能源对CO的有效性进行排名对于这些选项的_2种缓解措施，以轻型交通运输为例。与在电池电动汽车中使用可再生能源相比，用于将水还原为氢的可再生能源在将CO ₂转化为液体燃料时，其可有效减少CO ₂排放的四分之一。即使以100％的热效率实现，将CO ₂直接电还原为液体燃料，与电池电动汽车相比，缓解CO _2的效果也只有三分之一。