OXFORD REPORT: Trees & Soil – ultimate geoengineering tools

Conclusion:  The uncertainties and challenges associated with NETs deployment are significant. While NETs are capable of making a contribution to tackling climate change, particularly for ‘stubborn’ non-point source emissions, they are very unlikely to alter the sheer scale of mitigation required between now and 2050. While it is conceivable that there is significant technical potential beyond 2050, this is extremely uncertain.

Nevertheless, it makes sense to continue investing in the development of ‘low probability, high impact’ post- 2050 options in the hope that viable, large-scale NETs might be available in the unfortunate (but increasingly likely) event that they are required. The nature of these investments will vary by technology, but one thing is certain – without viable CCS large-scale post-2050 NETs will not be available. In addition to these observations, there are several related recommendations that carbon-intensive sectors and policymakers should take into account when considering NETs: 

First, ‘no-regrets’ NETs (NR NETs), which are characterised by low upfront capital costs, co-benefits (such as enhanced soil fertility), no CCS dependence, economic and environmental co-benefits, and fewer uncertainties, include afforestation, soil carbon improvements, and biochar. Even considering the potential for limited release of stored carbon in the future, they are the most promising NETs between now and 2050. To the extent that NR NETs create additional carbon budget, this should be reserved for the residual emissions (emissions after feasible mitigation actions) from important, but ‘stubborn’ non-point source emitters like agriculture and aviation. It is possible that NR NETs will have a niche role by 2050 offsetting these difficult to mitigate emissions sources. Policymakers and the owners and operators of assets in the relevant sectors should work together to maximise NR NETs deployment, minimise residual emissions from stubborn sectors, and develop plausible deployment pathways.

Secondly, the question of the cost of NETs and how those costs are shared is of profound importance for a range of issues, including the following: understanding how assets might be impacted by such costs; securing the cash flows and financing necessary for NETs deployment; and identifying implications for fairness and sustainable development. The challenge of commissioning and paying for conventional CCS demonstration plants highlights how difficult these issues are to resolve. International cooperation to address free riding and related issues is also required and this should be overlaid on to existing international processes and negotiations. 

Thirdly, successful NETs deployment would not mean business as usual for carbon-intensive assets. Sectors (and consumers) will have to pay directly or indirectly for the cost of mitigation actions, and quite probably the cost of negative emissions deployment, to address overshoot and stubborn emissions from non-point sources. NETs deployment addresses risk on the one hand (by extending carbon budgets), and creates it on the other (through new and uncertain costs). NETs should not be seen as a deus ex machina that will ‘save the day’. Consequently, businesses and investors need to factor carbon asset risk into their business planning and strategic asset allocation processes. Scenario planning and regular assessments of how carbon budgets are being translated into policy and regulation will be important,87 as is work to understand other environment-related risks that could strand assets. 

Fourthly, CCS is a key bottleneck for post-2050 NETs and this should be addressed to keep the option open for significant future deployment of DAC, Ocean Liming, and BECCS. While this option is uncertain, it is of sufficiently high potential impact to merit investment, as long as a possible dilemma can be resolved: deploying conventional CCS today results in positive net emissions and uses finite geological storage that might constrain storage capacity in the future; but unless conventional CCS is deployed at scale, the technology for negative emissions CCS might never be developed. The trade-off between these options and to what extent conventional 87 See: Caldecott, B. L., J. Tilbury and C. Carey (2014). Stranded Assets and Scenarios. Discussion Paper, Smith School of Enterprise and Environment, University of Oxford.Stranded Carbon Assets and Negative Emissions Technologies – February 2015 33 CCS needs to be deployed for DAC, Ocean Liming, and BECCS to be viable future options is an important area for future research. 

Finally, it is clear that attaining negative emissions is in no sense an easier option than reducing current emissions. To remove CO2 on a comparable scale to the rate it is being emitted inevitably requires effort and infrastructure on a comparable scale to global energy or agricultural systems. Combined with the potentially high costs and energy requirements of several technologies, and the global effort needed to approach the technical potentials discussed previously, it is clear that very large-scale negative emissions deployment, if it were possible, is not in any sense preferable to timely decarbonisation of the energy and agricultural systems.