Dispatch from the IPCC lead author meeting in Mexico City – CCUS and carbon removals

Paul Zakkour, an appointed lead author for the Intergovernmental Panel on Climate Change on new methodologies for measuring and reporting carbon capture, use, storage (CCUS) and carbon dioxide removals (CDR), provides a progress update and insider’s insight into how the process of developing guidance works.

In August lead authors of the much-anticipated 2027 IPCC CCUS-CDR Methodologies Report,[1] staff from the IPCC Task Force for National Inventories (TFI) and various IPCC observers gathered in Mexico City to discuss latest developments in these fields. CCUS and CDR are processes that can form a crucial part of many countries’ ability to achieve their nationally determined contributions (NDCs) to the Paris Agreement.

The gap

The suite of IPCC guidance dates back to 1996, providing vital methodological recipes for how countries can transparently, accurately, consistently and comparably measure, record and report anthropogenic emissions of greenhouse gases and removals by sinks. As requested in the Paris Agreement, countries should follow IPCC guidance when tracking and reporting progress towards achievement of their NDCs; that is, the reporting against the pledges that signatory parties make towards attaining the Agreement’s central temperature goal.

Yet there are gaps in the IPCC’s current recipe book for the treatment of several novel CDR and other CCUS methods (as highlighted, for example, by the Grantham Research Institute, CO₂RE, the IEAGHG and Carbon Counts). In 2024, the IPCC decided to address these gaps and, following an expert meeting and a subsequent scoping meeting in 2024 setting out a basis for the report, a mandate was agreed last year on how to proceed.

Developing the guidance

Work began in earnest in April 2026, when the group of lead authors got together for the first time at the UN Food and Agriculture Organization in Rome. That event laid out the main pieces for pulling together this complex job: an author team consisting of over 150 experts, clustered in four working groups and nine different thematic chapter teams, all tasked with exploring ways to update existing guidance and prepare new guidance, covering around 30 different parts of the IPCC guidelines.

Most of the work involves updating existing chapters, although around seven or eight new chapters can be expected to cover currently absent topics such as direct air capture of CO₂, capture of CO₂ from water, CO₂ utilisation and CO₂ mineralisation in rocks, buildings and other uses. Much of the existing guidance around CCS and bioenergy with carbon capture and storage (BECCS), contained in Volume 2 of the IPCC Guidance, will migrate to a new Volume 6, while other industrial uses could be woven into existing guidance around industrial processes and products (Volume 3). Land-based novel CDR technologies such biochar and enhanced rock weathering are anticipated to be integrated into existing chapters and guidance (e.g. for soil carbon in Volume 4).

All these updates also call for changes to the reporting architecture. Newly created national greenhouse gas sinks, pools, reservoirs, fluxes and flows need to be reflected in an updated recording system that is used by national greenhouse gas inventory compilers to log and track emissions. While seemingly mundane, the approach to reporting these new items is one of the more complex areas to be tackled within the new, additional, guidance.

Progress in Mexico City

The focus of discussion in Mexico City was on moving from the already-prepared zero-order drafts towards the next phase of report evolution. The zero-order draft texts, which were prepared ahead of the Mexico City meeting, contain the initial ideas for chapter headings and sub-headings, and notes on the section content and ideas for the calculation methods for the topic of interest. This time around the jigsaw started to take on more shape. Many cross-cutting items were identified, discussed and plans made to implement methods in a coherent and consistent way, a key stage in moving from zero-order to first-order drafts – the latter provide a solid basis for progress towards the final report and should ideally contain the first iteration of a complete chapter text.

From my perspective, topics posing challenging questions include start and end points of monitoring (e.g. because captured CO₂ and utilised or stored carbon can move across national boundaries through trade movements or through natural flows in the hydrosphere), the tracking and reporting of such movements (especially where products made from CO₂ or biomass are usually a small sub-set of a larger conventional product market), and ensuring consistency of treatment between analogous but parallel activities and products (e.g. in terms of other types of product flows, and the related methodologies and reporting approaches). Other groups and chapter teams are no doubt grappling with similar – and additional – issues.

Some of the more strategic challenges will take time and care to resolve, and at this stage teams are preparing first-order texts mindful that changes may emerge in the next round of discussions and drafting. As is typical of this sort of complex technical work, an iterative approach can be expected: hypothetical, idealised, concepts for reporting information will doubtless bump up against questions of implementation practicality. Are these data being collected or made freely available? At what level of aggregation? From which sources? What proxies might be available to use in the absence of clear data? Are there good practice assumptions to fill in gaps? This is seemingly a situation where form will have to follow function, rather than the other way around.

Next steps into 2027

After finalisation of the first-order drafts, expert reviewers will be invited to comment later in 2026. Thereafter, discussions move to Katmandu in January 2027 for the third lead author meeting. At this stage, many of the strategic questions should have further crystallised, and solutioning and alignment will be an important part of the group’s time in Nepal. Even then, much work will remain. I have the sense that the first-order drafts should only be considered as broadly directional. Some foundational issues remain in flux and consistency checks will be needed across different but similar topics, all of which will call for further alignment in the second-order drafts. These are scheduled for preparation in the first half of 2027, before the path to finalisation towards the end of the year.

[1] Or more precisely, the 2027 IPCC Methodology Report on Carbon Dioxide Removal Technologies, Carbon Capture, Utilization, and Storage for National Greenhouse Gas Inventories (Additional guidance)