What is The Difference Between Biogenic and Non-Biogenic Carbon?

Overview

Carbon is the building block of all organic compounds and moves continuously between living organisms, the atmosphere, the oceans, and the geological record. In carbon accounting and life cycle assessment, that carbon is separated into two categories — biogenic, originating in living biomass, and non-biogenic or fossil, originating in geological reservoirs.

This article defines both categories, gives practical examples across sectors, and explains how each is handled under ISO 14067, ISO 14040/14044, EN 15804, and the GHG Protocol — because getting this wrong is one of the most common errors in a product carbon footprint.

Biogenic carbon

Biogenic carbon is carbon that was fixed from atmospheric CO₂ by living organisms through photosynthesis, and is held in biomass — plants, trees, crops, animals, and the organic matter derived from them. It participates in the short carbon cycle, moving between atmosphere and biosphere over timescales ranging from a single growing season to a century or more, depending on the organism.

Because it was recently removed from the atmosphere, releasing it returns carbon that the atmosphere gave up in the recent past. Where the biomass source regrows, the release and the uptake balance over the growth cycle. Where it does not regrow, that balance breaks — which is the central caveat of the whole subject.

Practical examples of biogenic carbon

• Timber and engineered wood — structural timber, CLT, plywood, and particleboard, which store biogenic carbon for the service life of the building.
• Paper, board, and packaging — short-lived storage, with carbon released at end of life through decomposition or incineration.
• Natural fibres — cotton, wool, jute, hemp, and viscose from wood pulp.
• Bio-based plastics — PLA from corn starch, bio-PE from sugarcane ethanol, bio-PET.
• Biofuels — bioethanol, biodiesel, HVO, and biomethane from anaerobic digestion.
• Biomass energy — wood pellets, forestry residues, bagasse, and black liquor burned in pulp mills.
• Food and agricultural products — all crops, livestock products, and the carbon in food waste.
• Organic waste streams — the biogenic fraction of municipal solid waste, sewage sludge, and green waste.
• Biochar — biomass carbon converted to a stable form and applied to soil, where the storage is long-lived.
• Natural rubber, cork, bamboo, and starch-based adhesives.

Non-biogenic (fossil) carbon

Non-biogenic carbon is carbon held in geological reservoirs — coal, oil, natural gas, peat in some accounting frameworks, and mineral carbonates such as limestone. It also originated in living organisms, but hundreds of millions of years ago, and it has been isolated from the atmosphere ever since. It moves in the long carbon cycle, over timescales of millions of years.

Burning or processing it transfers carbon from that long-term reservoir into the atmosphere on a timescale of seconds, with no corresponding uptake on any human-relevant horizon. That is the entire basis of the climate problem: a one-way flow from geology into the atmosphere.

Practical examples of non-biogenic carbon

• Fossil fuels — coal, crude oil, diesel, petrol, natural gas, LPG, and petroleum coke.
• Conventional plastics and polymers — PE, PP, PET, PVC, polystyrene, and synthetic rubber.
• Petrochemicals — ethylene, propylene, methanol, solvents, and the chemical intermediates derived from them.
• Process CO₂ from cement — released when limestone is calcined to produce clinker, chemically rather than from combustion.
• Process CO₂ from lime, glass, and soda ash production, from the same carbonate decomposition.
• Metallurgical coke and carbon anodes — in steel and aluminium production, acting as reductant rather than fuel.
• Bitumen, asphalt, lubricants, and waxes.
• Synthetic fertilisers and industrial gases made from natural gas feedstock.
• Carbon black, graphite, and synthetic fibres such as polyester, nylon, and acrylic.
• Volcanic and geological CO₂ — a natural non-biogenic flux, though not anthropogenic.

The two compared

How LCA handles the distinction

This is where the difference stops being academic. Every product carbon footprint, EPD, and corporate inventory has to decide how to treat biogenic carbon, and the choice materially changes the result.

The ±1 convention

The standard approach records biogenic carbon uptake and release as a matched pair. Carbon absorbed into biomass enters the inventory as a negative flow; carbon released at end of life enters as a positive one.

Separate reporting is mandatory

Under ISO 14067, biogenic and fossil contributions must be reported separately, not merged into a single figure. EN 15804+A2, which governs construction EPDs, requires the same, with biogenic carbon content declared and uptake and release allocated to defined modules. A carbon footprint that presents one combined number without disclosing the split is not compliant with either.

Where the neutrality assumption breaks

1. 1Cradle-to-gate boundaries. If the study stops at the factory gate, biogenic uptake is counted but the eventual release is not — producing an artificially negative footprint. This is the single most common way biogenic accounting is abused.
2. 2No regrowth. If forest is cleared and not replanted, or harvest exceeds growth, the uptake never happens and neutrality is fiction.
3. 3Timing. A tree releases its carbon in an hour of combustion and takes decades to be reabsorbed. The atmosphere carries the extra CO₂ throughout that gap, producing real warming that a net-zero characterisation records as nothing.
4. 4Biogenic methane. When biogenic carbon decomposes anaerobically — in landfill, in a digester, or in ruminant digestion — it is released as CH₄, not CO₂. Methane has a far higher global warming potential, so the release is not neutral even though the carbon is biogenic. Biogenic CH₄ must always be counted.
5. 5Land use change. Converting forest or grassland to cropland releases soil and vegetation carbon that sits outside the product’s own carbon balance and frequently dwarfs it.

Timing and GWP-bio

Because the delay between release and reabsorption produces real radiative forcing, dynamic LCA methods and GWP-bio characterisation factors have been developed to account for it. These assign a non-zero value to biogenic CO₂ based on the rotation period of the biomass — short for annual crops, substantial for slow-growing forest. They are not yet default practice, but they are increasingly expected where the rotation period is long and the claim is significant.

Carbon storage in products

Where biogenic carbon is held in a durable product — timber in a building, for instance — the storage is real but temporary, and standards require the duration to be declared rather than treated as permanent removal. EN 15804 handles this through module-level reporting; ISO 14067 requires the storage period and the end-of-life fate to be stated.

Worked examples: how the split appears in practice

How the frameworks treat it

• ISO 14067 — requires biogenic and fossil contributions to be quantified and reported separately, with carbon storage and its duration declared.
• ISO 14040 and ISO 14044 — the framework governing boundary, functional unit, allocation, and the critical review that comparative claims require.
• EN 15804+A2 — mandates declaration of biogenic carbon content in construction products and allocates uptake and release across defined life cycle modules.
• GHG Protocol — biogenic CO₂ from combustion is reported separately from the scopes, while biogenic CH₄ and N₂O are reported within them.
• IPCC guidelines — national inventories account for biomass carbon in the land use sector rather than the energy sector, to avoid double counting.
• PAS 2050 and the GHG Protocol Product Standard — parallel product-level guidance with their own biogenic treatment rules.

Summary

Biogenic and non-biogenic carbon are chemically identical and climatically different, because of where the carbon came from and how quickly it goes back. Fossil carbon moves one way, from a reservoir isolated for millions of years into the active cycle. Biogenic carbon circulates, and can be genuinely near-neutral where the biomass regrows — but only where it regrows, only across a complete boundary, only where land use change is accounted for, and never when the release takes the form of methane.

For anyone producing a carbon footprint, the practical rules are short: report the two separately, take the boundary to end of life, count biogenic methane in full, evidence the sourcing, and state the storage duration rather than implying permanence. Those disclosures are what separate a defensible bio-based claim from one that will not survive review.