Assessing the feasibility of carbon dioxide mitigation options in terms of energy usage

Measures to mitigate the emissions of carbon dioxide (CO 2 ) can vary substantially in terms of the energy required. Some proposed CO 2 mitigation options involve energy-intensive processes that compromise their viability as routes to mitigation, especially if deployed at a global scale. Here we provide an assessment of different mitigation options in terms of their energy usage. We assess the relative effectiveness of several CO 2 mitigation routes by calculating the energy cost of carbon abatement (kilowatt-hour spent per kilogram CO 2 -equivalent, or kWh kgCO 2 e –1 ) mitigated. We consider energy efficiency measures, decarbonizing electricity, heat, chemicals and fuels, and also capturing CO 2 from air. Among the routes considered, switching to renewable energy technologies (0.05–0.53 kWh kgCO 2 e –1 mitigated) offer more energy-effective mitigation than carbon embedding or carbon removal approaches, which are more energy intensive (0.99–10.03 kWh kgCO 2 e –1 and 0.78–2.93 kWh kgCO 2 e –1 mitigated, respectively), whereas energy efficiency measures, such as improving building lighting, can offer the most energy-effective mitigation. Carbon emission reduction measures have widely differing energy consumptions that have not been systematically compared. Babacan et al. estimate comparable energy use per unit emission reduction of various emission reduction measures, from efficiency improvements to renewable electricity generation to carbon removal.