TRACEcdr - Methodoloy

Protocols are defined as documents that set quality requirements or guidelines for certification, carbon accounting, MRV or a component of these.

As a starting point to collecting protocols we used the overview of protocols from Arcusa and Sprenkle-Hyppolite (2022). We updated this list and collected additional protocols through newsletters and the websites of known protocol developers. We have not intentionally excluded any protocols based on language, but due to the search method, protocols in languages other than English are less likely to have been identified

To qualify for inclusion, protocols had to provide guidance for CDR activities that lead to net CO₂ removals from the atmosphere, or to CO₂ removals and avoided emissions, or to carbon capture and storage (CCS). Protocols on the latter were included because CCS facilitates CDR: methods such as direct air carbon capture and storage (DACCS) and biomass energy carbon capture and storage (BECCS) are currently reliant on CCS infrastructure, which is regulated by central and local governments (e.g. Class VI wells are regulated by the U.S. Environmental Protection Agency and the EU CCS and Emissions Trading System directives).

To determine whether a protocol adopts a consequential or attributional lifecycle perspective (cLCA or aLCA), we analysed six different components: the definition of the project boundary, the treatment of co-products, how the baseline is defined, and how additionality, permanence and leakage are managed/considered. A protocol's specific rules for baselines, additionality, permanence and leakage are ultimately defined by its scope and objective.

The following table briefly describes these analytical indicators and outlines how the aLCA/cLCA perspective differ in their treatment of each.

Analytical component

The protocol applying attributional LCA

The protocol applying consequential LCA

System boundary definition: Does the protocol include CO₂ captured from the atmosphere? Is the final store of carbon accounted for?

Static boundary including only direct CO₂ flows. Accounts for the final carbon store as a static inventory item.

Expanded boundary incorporating indirect, market-driven effects. Accounts for CO₂ captured from the atmosphere and changes in carbon storage.

Treatment of co-products: Are emissions allocated among co-products?

Allocates emissions among co-products using allocation factors (mass, energy, economic).

Uses system expansion to model the net consequences of producing co-products on the entire connected system.

Baseline definition: Is the baseline defined as zero or as a counterfactual scenario?

The baseline is a static point of comparison (e.g. a historical emissions level, a zero point, or a project-specific counterfactual) defined by the protocol's goal for attributing responsibility.

A dynamic reference. The baseline is a projected scenario of what would likely occur in the broader market without the project, used to estimate the decision's net impact.

Additionality (if considered by the protocol): How is the additionality (financial, regulatory) of a project measured?

Attribution-based test. Often uses a standardised performance benchmark or within-boundary comparison to attribute a reduction against the fixed baseline. Focuses on ‘what is’ as opposed to ‘what was.

Evaluates whether the project's activities and resulting carbon outcome were directly caused by the prospect of credit revenue or regulatory pressure (e.g. via investment analysis). Focuses on ‘what happened’ as opposed to ‘what would have happened.’

Permanence (if considered by the protocol): Are impermanence risks addressed? How are they managed?

For the duration of the credit or accounting period, stored carbon is treated as permanent. Reversal risks may be handled by separate insurance or buffer pool mechanisms outside the core accounting.

The risk of future reversal is explicitly modelled and discounted within the carbon accounting itself (e.g. using risk-adjusted discounts or insurance mechanisms).

Leakage (if considered by the protocol): Is project or market leakage considered? How is it mitigated?

Typically excludes effects outside the project's defined boundary. Focuses on flows within a fixed boundary. Market leakage is typically considered an external, unaccounted effect unless the protocol explicitly mandates its estimation.

Seeks to model and account for market leakage (e.g. a shift in activity causing emissions increases across regional or sectoral systems) as an integral part of the net impact calculation.

The components analysed above are simply diagnostic indicators of a protocol's underlying perspective (aLCA or cLCA) and not a binary pass or fail criteria for classification. Of the criteria, the most explicit indicator of a cLCA protocol is the definition of the system boundary, and specifically whether it includes indirect market effects and uses system expansion for co-products. Indeed, we found that all protocols that explicitly account for market leakage (e.g. from activity shifting) inherently employ an expanded system boundary, which is indicative of a cLCA perspective.

Protocols were assigned four options (Yes/No/Limited/Undefined) based on how the aforementioned components were handled within the protocol. Undefined protocols are either those not written in the English language (and therefore have not analysed) or were developed after this research began (typically those published after May 2025).

Definitions and Methodology