Evergreen

A registry is the ledger. A standard is the rulebook. For carbon dioxide removal (CDR), they are what turns “we removed a tonne of CO₂” into a serialized credit that someone can buy, count, and retire. A standard defines what counts as removal and how it must be measured. A methodology applies those rules to one specific process. Independent auditors check the project against the rules, and the registry issues the unit and tracks who owns it. When a buyer asks whether a credit is trustworthy, they are really asking whether each of these layers did its job. When a lender asks whether a project is bankable, much of the answer depends on whether a recognized standard has a methodology that fits the project’s process. ...

Additionality & Baselines: The Counterfactual That Decides Whether a Tonne Is Real Every carbon dioxide removal (CDR) credit is, at bottom, a claim about a parallel universe. Additionality asks whether the tonne of CO₂ subtracted from the atmosphere would have been subtracted anyway, absent the credit revenue. Baselines are the quantitative expression of that parallel universe: the reference scenario against which “extra” removal is measured. Get the baseline wrong and everything downstream — the price, the corporate net-zero claim, the registry’s reputation — is built on a number that doesn’t correspond to any physical reality. This is why buyers doing serious diligence spend more time on counterfactual assumptions than on capture chemistry, and why what “net zero” actually means depends on the integrity of the removals it invokes. ...

Durability & Permanence Durability (often used interchangeably with permanence) is the expected time that a tonne of carbon dioxide, once removed from the atmosphere, stays out of it. It is the single variable that most cleanly separates a nature-based credit priced in the low tens of dollars from an engineered credit priced in the high hundreds — and it is the variable that determines whether a corporate buyer can defensibly count a purchase against a net-zero claim. As Fankhauser et al. (2021) argue, “net zero” is only coherent if residual emissions are matched with removals of comparable longevity; a fossil CO₂ molecule released today and a soil-carbon credit that reverses in 30 years do not cancel out in any physically meaningful sense. ...

MRV: The Load-Bearing Wall of a CDR Credit Measurement, Reporting and Verification (MRV) is the set of procedures a carbon dioxide removal (CDR) project uses to answer three questions: how much CO₂ was actually removed from the atmosphere, how durably it will stay out, and how confident anyone can be in those numbers. It is the load-bearing wall between a project and a saleable credit. If MRV is weak, the credit is uninsurable and, increasingly, unsellable to serious buyers; if MRV is over-engineered, it eats margin that early-stage projects don’t have. Every argument about CDR quality — additionality, durability, leakage, uncertainty deductions — is ultimately an MRV argument. ...

Mineralization is the family of carbon dioxide removal (CDR) approaches that convert CO₂ into solid carbonate minerals — the same calcium and magnesium carbonates that make up limestone and dolomite. Once CO₂ is bonded into a carbonate lattice, it is thermodynamically stable on geological timescales, which is why mineralization sits at the durable end of the CDR spectrum alongside geologic injection. The pathway matters because it offers storage that does not depend on monitored plumes, biological uptake, or intact ecosystems — and because the reactive feedstocks (basalt, peridotite, olivine, steel slag, cement kiln dust, mine tailings, alkaline ash) are already abundant, often as waste streams. ...

Afforestation, reforestation and the wider “land sink” bucket Afforestation — planting trees where there were none in recent history — and its close cousin reforestation (replanting where forest was recently cleared) remain the largest single category of carbon removal sold today, by both tonnes issued and dollars transacted. The pitch is straightforward: trees pull CO₂ out of the air through photosynthesis and lock a fraction of it into wood, roots and soil organic matter for as long as the forest stands. The complications are equally straightforward: forests burn, get cut, get sick, and the carbon goes back. For a senior buyer comparing pathways, the central question is not whether trees sequester carbon — they obviously do — but how durable, additional and well-measured a given project actually is, and how that compares to engineered alternatives at 10–100× the price per tonne. ...

What BECCS is, and why it’s in the durable-CDR conversation Bioenergy with carbon capture and storage (BECCS) is the simple-sounding idea of growing plants (which pull CO₂ out of the air via photosynthesis), using that biomass to produce energy or fuel, capturing the CO₂ released when the biomass is processed, and putting that CO₂ somewhere it won’t come back out — almost always a deep saline aquifer or depleted hydrocarbon reservoir. The net result, if the accounting holds, is atmospheric CO₂ removed and geologically stored on the order of 10,000+ years. ...

What “Ocean CDR” actually means Ocean carbon dioxide removal is a family of techniques that use the sea — the planet’s largest active carbon reservoir, holding roughly 50 times more carbon than the atmosphere — to draw down atmospheric CO₂ and keep it down. The ocean already absorbs about a quarter of annual anthropogenic emissions through air-sea gas exchange (Friedlingstein et al., 2023). Ocean CDR approaches either accelerate that natural uptake (by shifting seawater chemistry) or use biology to fix carbon and export it below the mixed layer, where it stays out of atmospheric contact for centuries to millennia. The appeal for buyers chasing durable removal is straightforward: the storage reservoir is enormous, and the residence times — particularly for bicarbonate ion in the deep ocean — are on the order of 10,000 years (Siegel et al., 2021). ...

What “soil carbon” means in a CDR context Soil carbon as a removal pathway is the deliberate addition — or protection — of organic carbon in agricultural and grassland soils so that atmospheric CO₂ ends up stored as soil organic matter rather than circulating in the air. In practice, almost every commercial project in the directory today is doing this through biochar: pyrolysing biomass into a stable, carbon-rich solid and burying it in farmland. A smaller share of projects pursue management-based sequestration (cover crops, no-till, compost, agroforestry) where the carbon gain comes from shifting the balance between plant input and microbial decomposition. The two approaches share a destination — carbon in soil — but the durability profiles and the science behind them are very different, which is the single most important thing for a buyer or journalist to internalise before going further. ...

Direct Air Capture (DAC) is the use of engineered equipment — fans, sorbents, solvents, or electrochemical cells — to separate carbon dioxide from ambient air, concentrate it, and hand it off to either permanent storage or industrial use. Unlike point-source capture at a power plant or cement kiln, DAC has no flue gas to draw from: it works against an atmospheric concentration of roughly 425 ppm, which is the central reason it is both energy-intensive and, when paired with geological storage, one of the most durable carbon dioxide removal (CDR) options available. For buyers and policymakers building portfolios with century-plus permanence, DAC sits alongside mineralization and bio-oil sequestration as a small-but-growing share of the durable removals market. ...