Biogenic Emissions Reporting: Why Biogenic CO₂ Is Accounted Separately

Biogenic emissions reporting is one of the most consequential accounting distinctions in corporate disclosure — and one of the most consequential product distinctions in Greentruth's QET-RNG. This page explains what biogenic emissions are, why they are reported separately from fossil emissions under the GHG Protocol and IPCC methodology, and how a QET-RNG preserves a clean biogenic carve-out across every framework that asks for it.

Biogenic emissions reporting, in one paragraph. Biogenic emissions are CO₂ (and, in some cases, CH₄ and N₂O) released from biogenic carbon sources — renewable natural gas, biomass, biofuels, and other materials whose carbon was recently absorbed from the atmosphere. Under the GHG Protocol Corporate Standard and IPCC methodology, biogenic CO₂ is treated as part of the short carbon cycle and reported on a separate line from a reporter's fossil-only inventory. Greentruth's QET-RNG records the biogenic carve-out as a first-class attribute on the token, so reporters can present a clean fossil-only number where their framework requires one — and a complete biogenic line where the framework requires that.

For the foundational QET overview

Biogenic emissions reporting is the practice of separating CO₂ emissions from biogenic carbon sources from CO₂ emissions from fossil carbon sources in a corporate GHG inventory. The motivation behind biogenic emissions reporting is straightforward: the two have different atmospheric implications.

• Biogenic CO₂ comes from carbon that was recently absorbed from the atmosphere — by a crop, a tree, a microbe, a digester feedstock — and is then re-released when the resulting biomass is combusted, decomposed, or otherwise broken down. It is part of the short carbon cycle.
• Fossil CO₂ comes from carbon that was sequestered over geological timescales and is re-released into the atmosphere on a much faster cycle than it was removed.

Treating them as identical in a corporate inventory would obscure the difference that climate-policy frameworks actually care about. So they are reported separately — a fossil CO₂ line that contributes to the corporate emissions number, and a biogenic CO₂ line reported alongside it as a memo item.

Methane and nitrous oxide from biogenic sources are treated differently from biogenic CO₂ — they are typically included in the fossil-equivalent inventory because, under the relevant frameworks, their warming effect is not netted by the short carbon cycle.

The short carbon cycle is the period — typically years to decades — over which carbon moves from the atmosphere into biomass and back. Under most credible GHG accounting frameworks, biogenic CO₂ is treated as carbon-neutral over a complete short carbon cycle because the CO₂ released by combustion was previously absorbed from the atmosphere as the feedstock grew.

That assumption is conditional. It depends on:

• Sustainable feedstock management — without it, the cycle is not closed.
• Methane and N₂O from the biogenic source — these are not netted by the short carbon cycle and remain in the inventory.
• Land-use change — converting land to biofuel feedstock can release stored fossil carbon. Frameworks treat this separately.

For Greentruth specifically, the relevant biogenic carbon source is renewable natural gas — biomethane produced from organic feedstocks (agricultural waste, landfill gas, wastewater, food waste, and similar). RNG combustion releases biogenic CO₂; the methane content of the gas itself, where it leaks rather than combusts, is treated as a methane line item under the framework's relevant biogenic methane rule. (For fossil natural gas, the accounting is different: see QET-NG.)

Modeled defaults vs measured CI values · Mass-balance chain-of-custody for RNG

The GHG Protocol Corporate Standard treats biogenic CO₂ as a separate reporting line. Reporters disclose:

• Fossil CO₂ in the main inventory — included in Scope 1, Scope 2, and Scope 3 as applicable.
• Biogenic CO₂ as a memo item — reported alongside the inventory, not netted against it.
• Biogenic CH₄ and N₂O in the main inventory — these are not part of the short carbon cycle assumption and remain in the fossil-equivalent total.

The structural detail matters: presenting a clean fossil-only line is not optional under the GHG Protocol. It is the framework's expected treatment. Greentruth's QET-RNG is designed so that the biogenic carve-out is preserved at the token level — the buyer doesn't have to reconstruct it.

The full GHG Protocol explainer

GHG Protocol biogenic guidance

The IPCC's 2006 Guidelines for National Greenhouse Gas Inventories (and the 2019 Refinement) handle biogenic carbon at the national-inventory level, with similar logic. National-inventory practice carries forward into the GWP factors corporate reporters use — and those factors matter for the conversion from CH₄ and N₂O to CO₂-equivalents.

Greentruth anchors to IPCC AR5 GWP100 factors:

• CH₄ = 28
• N₂O = 265

These are the factors specified in the QET-RNG methodology (v2.1.2). They apply to CH₄ and N₂O emissions across the token's well-to-pipeline-injection scope, while biogenic CO₂ is kept on a separate accounting line per the GHG Protocol biogenic guidance.

A common error in biogenic emissions reporting is using a more recent IPCC report's GWP factors than the framework in force actually requires. Biogenic emissions reporting is methodology-versioned, not "current-IPCC-by-default." Greentruth's methodology versioning makes that error structurally hard to commit: each QET records the exact GWP factor set used at issuance, so framework exports can be reconstructed against the version of each framework in force at retirement.

For producers and buyers of renewable natural gas, ethanol, and other biogenic fuels, the biogenic carve-out is the difference between a credible carbon-negative or carbon-neutral claim and a number that gets pushed back by an auditor.

Two specifics shape the practical work:

• A carbon-negative RNG claim is only credible if the biogenic carve-out is preserved. A RNG pathway can score below zero in carbon intensity when avoided methane emissions (for example, from a landfill or dairy digester) exceed the fossil-equivalent emissions of producing and delivering the fuel. That arithmetic only works when biogenic CO₂ is correctly carved out.
• Combustion is out of scope of the QET-RNG methodology. The token's scope is well-to-pipeline-injection. End-use combustion is handled in the buyer's downstream accounting, alongside the biogenic CO₂ line the methodology preserves.

For pathway holders submitting to California's Low Carbon Fuel Standard, biogenic methane treatment is specifically defined by CARB — and is the subject of the QET-LCFS extension methodology that runs on top of the QET-RNG core.

How LCFS compliance works on Greentruth · For transportation buyers specifically

A QET-RNG carries biogenic emissions reporting as a first-class attribute on the token. The biogenic carve-out is not an export-time transformation — it is encoded at mint and travels with the certificate through transfer, retirement, and framework export.

What the token records:

• Biogenic CO₂ line item — separated from fossil CO₂ for the underlying physical unit.
• CH₄ and N₂O lines — multi-pollutant accounting in kgCO₂e/MMBtu using IPCC AR5 GWP100 factors.
• Pathway and feedstock category — so the framework export can flag any land-use change or methane treatment specifics the buyer's framework requires.
• Methodology version and verifier of record — under ISO 14064-3 reasonable assurance.

The buyer's framework export — whether for GHG Protocol Scope 1, SBTi-aligned Scope 1 reduction, TCR's General Reporting Protocol, or CSRD ESRS E1 — receives biogenic and fossil lines in the form each framework expects.

The full QET-RNG methodology

Biogenic emissions reporting is treated similarly across frameworks, but each one has its own specifics. The QET-RNG carve-out is designed to feed all of them.

How the SBTi treats biogenic emissions under C11

How the TCR GRP §B-7 alignment works

The full framework comparison