The European Academies Scientific Advisory Council released an excellent report on “Negative emission technologies: What role in meeting Paris Agreement targets?”
This excellent paper has a summary directly stating:
Climate scenarios that keep global warming within Paris Agreement limits rely on large-scale application of technologies that can remove CO2 from the air on a huge scale. This is necessary to compensate for the inadequacy of currently planned mitigation measures, which would lead to cumulative emissions of greenhouse gases (GHGs) overshooting the levels that are compatible with avoiding dangerous climate change. The credibility of such scenarios needs to be properly assessed since relying on such technologies to compensate later for failures to adequately mitigate emissions has serious implications for future generations. Having reviewed the scientific evidence on several possible options for CO2 removal (CDR) using negative emission technologies (NETs), we conclude that these technologies offer only limited realistic potential to remove carbon from the atmosphere and not at the scale envisaged in some climate scenarios (as much as several gigatonnes (one billion or 109 tonnes) of carbon each year post-2050). Negative emission technologies may have a useful role to play but, on the basis of current information, not at the levels required to compensate for inadequate mitigation measures. Implementation is also likely to be location-, technology- and circumstance specific. Moreover, attempts to deploy NETs at larger scales would involve significant uncertainties in the extent of the CDR that could be achieved, as well as involving high economic costs and likely major impacts on terrestrial or marine ecosystems. The dominant role assigned in IPCC integrated assessment models to NETs (in particular bioenergy with carbon capture and storage: BECCS) has yet to take fully into account these limitations. Scenarios and projections of NET’s future contribution to CDR that allow Paris targets to be met thus appear optimistic on the basis of current knowledge and should not form the basis of developing, analysing and comparing scenarios of longer-term energy pathways for the European Union (EU).
Future scenarios without NETs, however, show the great difficulty of reaching net zero emissions of CO2 by 2050, which is why NETs have received much attention recently. However, the limited potential for CDR underlines the need to strive as hard as possible to mitigate emissions (through energy efficiency and energy saving by technical and regulatory measures, rapid deployment of renewable energies, land use management, reducing emissions of other GHGs, etc.) to make any need for NETs more manageable.
- Firstly, the EU (and other Contracting Parties) should concentrate on rapidly reducing GHG emissions as laid out in the Paris Agreement’s 5-year review process of national emission reduction plans.
- Secondly, some of the most technologically credible approaches involve increasing soil carbon and forest biomass, but we remain in an era where deforestation and soil degradation are continuing to add substantial quantities of GHGs. Clearly, as well as considering forests to remove substantially larger amounts of CO2, humanity needs to control the loss of forests, while stopping soil degradation and restoring soil carbon levels requires this to be included in the criteria for agricultural management.
- Thirdly, we emphasize the importance of solving remaining technical challenges in removing CO2 from point sources via carbon capture and storage (CCS), and developing viable business models for CCS implementation to remove CO2 from fossil-fuel power station emissions and from other energy intensive industries (cement, steel, etc.). Despite the inherently higher efficiencies of CDR when applied to concentrated point sources, CCS plans in Europe have been shelved so that whatever experience is being gained globally is outside Europe. The loss in momentum in implementing CCS technologies not only has serious implications for mitigation pathways, but also one of the most commonly cited NETs (BECCS) assumes the availability of cost effective ’off-the shelf’ CCS, while another (direct air capture) relies on the widespread availability of CO2 storage. At present, economic incentives for deploying CCS are inadequate (whether through the very low carbon price or targeted government support), while those for NET development are lacking.
Despite the limitations of NETs, halting increases in the concentration of GHGs in the atmosphere remains a race against time, and humanity will require all possible tools to limit warming to within Paris Agreement targets. NETs include measures (re/afforestation and increasing soil carbon contents) that are able to be encouraged now with appropriate policy support (such as the ‘4 per mille’ initiative), and the EU should consider more effective measures for enhancing carbon stocks (as noted in our recent report on multifunctionality of the EU’s forests (EASAC, 2017)), as well as incorporating consideration of soil carbon levels in agricultural policy. The other NETs are at different stages of research and development where lead times are long, and thus, even now, it is appropriate to work (in conjunction with the industries potentially providing or applying such technologies) to identify the best technologies and the conditions under which they can contribute to climate change mitigation. While this analysis considers the potential role of NETs at the global scale, our analysis is relevant to the EU’s policies on CCS, on research priorities, and on the EU’s position within international bodies, including the UN Framework Convention on Climate Change, where a political discussion on the potential role of NETs and on how to translate any global CO2 removal targets to national actions will be needed.