Carbon capture and storage (CSS) from fossil fuel power stations is considered crucial to mitigating the effects of climate change. However, a new study published on 8 April in Nature Energy suggests resources currently directed toward the development of CSS would be better spent on renewable energy technologies, such as wind turbines and solar panels, and the energy storage capabilities to support them (1).
Carbon capture expectations are not meeting reality
According to the authors, carbon capture technologies are currently considered a fundamental component of future energy portfolios. However, the authors point to a “considerable gap between modelled expectations for CCS and practice” around the world. For example, China is expected to bring into action a huge amount of CCS power by 2050 but does not have any large-scale CCS in operation at present.
This raises the question of whether CSS technologies can be scaled quickly enough to help meet targets set out in the 2015 Paris Climate Change Agreement ― current climate change models predict that carbon capture and storage will need to contribute 5 to 55 per cent to limit global warming to within 2 degrees Celcius above pre-industrial levels.
Energy return on energy invested
The international team of researchers from Lancaster University, Khalifa University, Clemson University, UiT The Arctic University and the University of Florence used something called the energy return on energy invested (EROEI) ― the ratio of usable energy to the energy invested in the construction, operation, and fuel procurement for power plants.
Based on the EROEI, they compared the energy performance of fossil fuel power plants with CCS versus scalable renewable energy. In addition, they considered various renewable energy sources combined with different energy storage methods including batteries, hydrogen, or pumped hydro-power.
The researchers found that the EROEI of electricity from different fossil-fuel-based power plants with CCS (assuming that 90% of CO2 is captured) is “unfavourable” compared to the current EROEI of scalable renewable energy resources (mainly solar and wind) without storage.
The main reason for this is the additional loss of energy associated with building and operating CCS processes. As well as the energy needed to produce CCS equipment, such as pipes and compressors. This results in lower net energy output from coal and gas power stations with carbon capture. Whereas, renewable technologies such as solar panels and wind turbines, even in only moderately efficient locations, provide better energy returns.
What is the best approach?
The authors conclude that “it is more valuable, energetically, to invest available energy resources directly into building new renewable energy (and storage) capacity rather than building new fossil-fuel power plants with CCS.”
Adding that “Given its net energy disadvantages, carbon capture and storage should be considered a niche and supplementary contributor to the energy system, rather than be seen as a critical technology option as current climate agreements view it.”
Therefore, future policies should prioritise projects with the highest EROEIs. In other words, future investments should be geared towards self-sustaining renewable energy resources, instead of focusing on fossil fuels, which are gradually being depleted.
(1) Sgouridis, S. et al. Comparative net energy analysis of renewable electricity and carbon capture and storage. Nature Energy (2019). DOI: 10.1038/s41560-019-0365-7