As companies and countries work toward net-zero targets, many will still face residual greenhouse gas (GHG) emissions — those that are too difficult or costly to abate with current technologies or practices. Achieving net zero will therefore require counterbalancing these emissions with carbon dioxide removal (CDR). A central challenge is determining how different types of residual emissions should be matched with different forms of CDR. The ‘like-for-like’ concept is one proposed framework.What is the Like-for-Like Concept?The like-for-like concept holds that the type of CDR used to counterbalance residual GHG emissions should reflect the properties of those emissions.One formulation focuses on atmospheric lifetime. Carbon dioxide (CO2), which persists in the atmosphere for centuries to millennia, would need to be counterbalanced by removals with comparable durability, such as direct air capture with geologic sequestration. These are often referred to as high-durability removals.In contrast, methane (CH4) — which has a much shorter atmospheric lifetime (approximately 10 years) — could be addressed through lower-durability approaches, such as reforestation, which carry a higher risk of reversal over time.A second formulation of like-for-like focuses on the source of emissions rather than the gas itself. Under this approach, emissions from land use could be counterbalanced by land-based removals, like forest restoration, which are generally less durable. In contrast, emissions from geologic sources — such as fossil fuels or cement production — would be counterbalanced by removals that include geologic sequestration. Across both formulations, CO2 emissions from fossil fuel combustion would need to be counterbalanced by high-durability removals, such as those with geologic or geochemical carbon sequestration. However, emissions from deforestation or CH4 are treated differently depending on the framework. In some cases, there is not yet a clear consensus on the most appropriate form of CDR to address specific GHGs or emissions sources.Why Is the Like-for-Like Approach Being Proposed?The like-for-like approach aims to provide guidance on how different CDR types should be used to achieve net zero, with the goal of ensuring that climate benefits match climate impacts and that net zero can be sustained in the long term.One aspect is to avoid overreliance on nature-based removals. These approaches generally carry a higher risk of reversal — meaning that stored CO2 may be released back into the atmosphere — and offer shorter storage durations (typically decades to a century) compared to high-durability CDR methods. As a result, they are not well suited to counterbalance CO2 emissions that persist in the atmosphere for centuries.There are also limits to how much CO2 can be sequestered through land-based approaches. The capacity of ecosystems to sequester carbon is finite and declining due to climate change and ongoing land-use change. As such, it’s difficult to project the stability of these carbon sinks over time. Relying on these approaches to counterbalance emissions from geologic sources can create an imbalance between carbon cycles operating on different timescales.This distinction can be understood in terms of the ‘fast’ and ‘slow’ carbon cycles. The fast carbon cycle moves carbon between the atmosphere, ecosystems and oceans over relatively short timescales, while the slow carbon cycle describes the long-term movement of carbon between the atmosphere and Earth’s interior. Using fast-cycle removals to counterbalance slow-cycle emissions risks saturating the capacity of ecosystems to sequester carbon. Relatedly, because a large share of historical and current emissions originates from fossil fuel combustion, some argue that continued fossil CO2 emissions should be counterbalanced primarily with removals that return carbon to geologic storage. This concept is often referred to as ‘geologic net zero.’ What Would be the Implications of a Like-for-Like Approach?Global emissions in 2023 were approximately 50.7 GtCO2e, of which just under 75% (37 Gt) was CO2. The remainder consisted of non-CO2 gases, including CH4 (9.8 Gt), nitrous oxide (2.8 Gt) and fluorinated gases (1.4 Gt).Under global net-zero scenarios assessed by the IPCC, CO2 represents a smaller share of residual emissions, while non-CO2 emissions — particularly CH4 — make up a larger proportion. In scenarios limiting warming to 1.5 degrees C with overshoot, the median level of residual emissions at net zero total about 15 Gt and are roughly evenly split between CO2 (7.4 Gt) and non-CO2 gases (7.5 Gt), with CH4 comprising approximately 4.4 Gt of the latter (around 30% of total residual emissions). If like-for-like is implemented based on atmospheric lifetime, a portion of required removals — at least 25% globally — could be met with lower-durability approaches such as reforestation. However, most removals would still need to have high durability.In the United States, emissions today and at net zero show a similar pattern to global emissions. Total emissions in 2024 were 5.2 GtCO2e, with 75% from CO2 and 13% from CH4. The 2021 U.S. Long-Term Strategy outlines a pathway to net zero by midcentury, with roughly 0.7 Gt of CO2 and 0.4 GtCO2e of CH4 remaining.Where Has the Like-for-Like Approach Been Proposed?The like-for-like approach has been proposed in state and federal legislation in the United States, as well as in the European Union.At the U.S. federal level, a proposed carbon border adjustment bill introduced in 2025 includes provisions allowing industrial emitters to reduce liability through the purchase of carbon removal. The extent of liability reduction depends on the durability of the removal, resembling a form of like-for-like matching. In California, Senate Bill 285 (introduced in 2025) proposed guidelines for matching the durability of CDR used to counterbalance residual emissions under the state’s 2045 net-zero target. The bill would have required matching removal types either to the source of emissions or to the atmospheric lifetime of the emitted GHGs. Emissions from fossil fuels or mineral sources (such as cement production) would require durable CDR, while emissions from biological sources and short-lived climate pollutants could be addressed through land-based removals. This approach effectively combines both like-for-like formulations. The bill also defined ‘permanent’ storage as lasting more than 100 years, allowing forest restoration to qualify as durable under specific conditions.In the EU, the European Parliament’s position on the Green Claims Directive includes a requirement that companies use permanent removals to counterbalance fossil emissions, although the directive has not yet been finalized. As the EU considers integrating CDR into its Emissions Trading System, the role of like-for-like is also under discussion. While these efforts differ in design, they reflect growing interest in incorporating durability and equivalence into carbon removal and other climate-related policy.What Are Some Complexities of the Like-for-Like Approach?Despite its intuitive appeal, the like-for-like approach raises several challenges.One key issue is how to convert non-CO2 gases into CO2-equivalent terms to determine the required level and type of CDR to counterbalance them. The choice of conversion metric — such as global warming potential over 20 years (GWP20) or 100 years (GWP100) — has significant implications.CH4 illustrates this challenge. It has a short atmospheric lifetime but a strong near-term warming effect, in contrast to CO2’s long atmospheric lifetime and sustained warming impact. Using GWP100, CH4 is approximately 28-30 times more potent than CO2, as its short-term warming is averaged over a longer period. Using GWP20, CH4 is estimated to be 81 to 86 times more potent, reflecting its stronger impact over a shorter timeframe and more closely matching CH4’s actual lifetime in the atmosphere.If GWP20 is used, more CDR would be required to counterbalance each metric ton of CH4, but that removal could be shorter in duration. This allows for closer temporal alignment between the warming impact of emissions and the cooling benefit of removals.Another limitation is that natural systems cannot indefinitely absorb carbon. Even though CH4 is short-lived, relying on biospheric sinks to counterbalance CH4 over time risks exceeding their capacity. This suggests that, in the long run, less than 100% of CH4 — and potentially other short-cycle emissions — can be addressed through lower-durability CDR.Another complexity is how and when like-for-like requirements would be implemented. For example, such requirements could apply only at net zero, be phased in gradually, or be required in the near term. Finally, like-for-like has been criticized for implying that emissions and removals are interchangeable. In practice, emissions should be reduced or eliminated wherever possible, and CDR should be reserved for residual emissions that cannot be avoided. What’s Next?The like-for-like approach provides one framework for guiding how CDR is used to achieve net-zero goals. While current CDR deployment remains far below projected needs, developing a shared understanding of how to appropriately match emissions and removals will be critical to ensuring credible and durable net-zero outcomes.