Negative emissions technologies - Grantham Briefing Paper 8

Negative emissions

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It seems increasingly likely that concentrations of CO₂ and other greenhouse gases (GHGs) in the atmosphere will overshoot the 450 ppm CO₂e target, widely seen as the upper limit of concentrations consistent with limiting the increase in global mean temperature from pre-industrial levels to around 2°C.

Therefore, in the future, in order to correct for the overshoot it may become necessary to remove CO₂ from the atmosphere. This would be achieved by capturing CO₂ from the air; historical CO₂ emissions can then be sequestered and the aggregate amount of CO₂ in the atmosphere reduced – so-called negative emissions.

From a UK perspective, a robust strategic plan is needed to achieve the UK target of an 80% reduction in GHG emissions on 1990 levels by 2050. Negative emission technologies ought to be considered as part of the technology mix needed to achieve these reductions at least cost.

This Briefing Paper deals with the practicalities of certain classes of negative emissions technologies and addresses the likely energy, economic, environmental and policy implications of the use of specific technologies. The main objectives of the paper are to introduce the concept and its relevance to climate change mitigation, to describe and evaluate alternative technologies, and to estimate likely costs and other performance measures.

A range of options have been identified, which are at various stages of development. The Paper presents the output from an initial scoping study, which aims to provide consistent performance and cost estimates on feasible options for capturing CO₂ from the air, as well as identify the scale at which these technologies could eventually remove CO₂. The study is based around case studies of five different technologies, which have been chosen because they exemplify alternative strategies for achieving negative emissions: Artificial Trees; The Soda/Lime Process; Augmented Ocean Disposal; Biochar; and Biomass Energy with Carbon Capture and Storage (BECCS). The review does not consider reduced emissions from deforestation and forest degradation plus enhanced forest carbon stocks (REDD+), but these strategies are nonetheless important and should be considered within a suite of mitigation measures. Furthermore, Solar Radiation Management (SRM) technologies, which aim to reduce the incident energy on the earth, are not included and raise significant additional issues and concerns.

Contents

• Executive summary
• Introduction
• Why Negative Emissions?
• Technology Overview
• Scalability and Rollout Potential
• Policy and International Context
• Research Agenda and Technical
• Challenges
• Conclusions

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