Carbon accounting for negative emissions technologies

Abstract

Negative emissions technologies (NETs) are an essential part of most scenarios for achieving the Paris Agreement goal of limiting warming to below 2°C and for all scenarios that limit warming to 1.5 °C. The deployment of these technologies requires carbon accounting methods for a range of different purposes, such as determining the effectiveness of specific technologies or incentivising NETs. Although the need for carbon accounting methods is discussed within the literature on NETs, there does not appear to be a clear understanding of the range of different accounting challenges. Based on a systematic literature review this study identifies five distinct accounting issues related to NETs: 1. estimating total system-wide change in emissions/removals; 2. non-permanence; 3. nonequivalence of 'no overshoot' and 'overshoot and removal'; 4. accounting for incentives for NETs; and 5. the temporal distribution of emissions/removals. Solutions to these accounting challenges are proposed, or alternatively, areas for further research and the development of solutions are highlighted. One key recommendation is that carbon accounting methods should follow a 'reality principle' to report emissions and removals when and where they actually occur, and an important overall conclusion is that it is essential to use the correct accounting method for its appropriate purpose. For example, consequential methods that take account of total system-wide changes in emissions/removals should be used if the purpose is to inform decisions on the deployment or incentivisation of NETs. Attributional methods, however, should be used if the purpose is to construct static descriptions of possible net zero worlds.

Assessing the carbon capture potential of a reforestation project

“…Brander et al argue that businesses should only report CO 2 capture figures that have been already and permanently captured 64 . An attraction of carbon storage in the above-ground biomass of forests is that it can be readily assessed using remote sensing techniques supported by surveys 65 .…”

“…An attraction of carbon storage in the above-ground biomass of forests is that it can be readily assessed using remote sensing techniques supported by surveys 65 . However, as discussed earlier, the above-ground C credits associated to the future growth of reforestation projects come with associated risks, and the figures should be frequently monitored and evaluated to ensure appropriate accuracy 64 , 66 . Another solution would be to set up a carbon stock discount rate of newly planted forests based on the risks of plot destruction.…”

Who Is Paying for Carbon Dioxide Removal? Designing Policy Instruments for Mobilizing Negative Emissions Technologies

“…5. Ensure robust and comparable measuring, reporting, verification and accounting of results to track national, regional and global progress toward net-zero emissions (Brander et al, 2021). 6.…”

Undoing Equivalence: Rethinking Carbon Accounting for Just Carbon Removal

“…A key concern with this equivalence pertains to the different timescales involved: fossil carbon sinks are essentially permanent (or inert) if left unused, while biotic carbon is part of the shortterm (or active) carbon cycle. While accounting systems try to deal with the risk of reversal from biotic sinks in various ways, for example through temporary crediting, these solutions do not take away the long-term uncertainties involved (Brander et al, 2021). The different temporal characteristics of fossil vs. biotic carbon represent a fundamental barrier to equivalence.…”