Carbon dioxide removal (CDR) is essential for climate change mitigation, but no single standardized methodology exists for evaluating project-level net carbon removal from the atmosphere.
Lawrence Livermore National Laboratory (LLNL) scientists and collaborators from Lawrence Berkeley and National Renewable Energy national laboratories and UC Berkeley, have looked into the state of evaluating the climate impact of CDR projects (also referred to as carbon accounting) and provide a common knowledge base, framework and set of metrics for CDR assessment. Their research team's perspectives were recently published in the journal One Earth.
CDR, in theory, involves simple-to-track flows of carbon out of the atmosphere, where it is causing climate change, to a stable storage location where it can no longer have negative climate impacts. The simplest example of this is Direct Air Capture and Storage (DACS), which can pull CO2 directly out of the air, compress it and inject it very deep underground, often into the same geologies where fossil fuels had been stored for millennia. Another example of CDR is Biomass Carbon Removal and Storage (BiCRS), which can process plant material (containing carbon that was absorbed from the atmosphere) and convert it to a more stable and/or storable form that may include geologic carbon storage. A mineralization-based CDR approach, such as the one that LLNL is researching in California, exposes specific rocks that would otherwise never interact with the atmosphere, which then naturally converts the ambient CO2 into safe, stable minerals, such as magnesium carbonate, the primary ingredient in antacids.
"But not all projects that include activities that remove CO2 from the atmosphere actually result in net removal of CO2 from the atmosphere," said LLNL scientist and co-author Kim Mayfield, "which is why this paper is important - to illustrate how stringent we need to be with carbon accounting boundaries to ensure that governments or companies that invest in CDR projects to counteract their hardest-to-abate emissions are, in fact, causing a net removal of carbon from the atmosphere."
The paper outlines the basics of these carbon accounting methodologies, applied to a range of CDR methods, to evaluate their effectiveness in achieving a net flux of CO2 out of the atmosphere and into stable storage. The paper goes into detail with examples for applying this framework to DACS, BiCRS and land-based mineralization systems.
The paper also states that CDR should be the last climate change mitigation strategy, used only after all cheaper options for mitigation and decarbonization have been exploited. However, the reality of technology development and scale-up necessitates that CDR methods be pursued and stress-tested now so that they are poised to operate at the scales needed in several decades.
"In response to this need, a CDR ecosystem of suppliers, verifiers and buyers is emerging, but - as national laboratories - it is our responsibility as unbiased arbiters to construct robust guidelines for the evaluation of CDR projects that represents the 'platinum standard' for what CDR projects should account for to achieve net beneficial climate impacts," Mayfield said
At the most fundamental level, CDR projects should deliver a net flux of CO2 from the atmosphere to stable storage after accounting for the actual energy, materials and environment used for a project. A standardized process for quantifying net CO2 removal is important for the development of a trusted CDR industry.
"CDR technologies are essential to address climate change and serve to compensate for legacy and the hardest-to-abate greenhouse gas emissions," said LLNL scientist and co-author Corey Myers. "Although near-term emissions reductions are the priority, development and deployment of CDR must proceed now to ensure effective technologies and guardrails are ready at scale in the future."
LLNL scientist Sarah Baker also contributed to this research. The project is funded by the DOE Office of Technology Transitions in collaboration with the Office of Clean Energy Demonstrations and the Office of Fossil Energy and Carbon Management.
