Biogenic Carbon
Carbon that plants absorb and that stays stored in wood and other bio-based products.
Quick Answer
Biogenic carbon is carbon that plants absorb from the atmosphere through photosynthesis and that remains stored in biomass, such as the wood in a building. In carbon assessments it is reported separately from fossil carbon, and its treatment, whether counted as storage or as a neutral flow, is a methodological choice that affects results.
The Full Picture
Biogenic carbon matters because wood, bamboo, straw, and other bio-based products are made of carbon that came from the air. Fossil carbon, by contrast, adds new carbon to the atmosphere from stored geological sources. Distinguishing the two is the basis for treating bio-based materials differently in carbon accounting.
In life-cycle assessments following EN 15804-type rules, biogenic carbon is reported as its own indicator, separate from fossil GWP. Carbon uptake during tree growth appears as a negative value and is released again at end of life if the wood is burned or decays. Whether to count the stored amount as a benefit depends on the assumed end-of-life scenario and the study period.
There is real debate. Some accounting treats biogenic carbon as neutral over time, assuming forests regrow. Others argue the timing matters, since harvesting releases or forgoes carbon now while regrowth takes decades, and that sustainable forestry sourcing is critical to any claim. Because of this, reported timber carbon figures can differ depending on method, and transparent reporting is more reliable than a single headline number.
For project teams, the practical points are to ask which method an EPD or carbon calculation uses, to separate fossil and biogenic results when comparing options, and to document the wood's sourcing, such as certified forestry. Timber structures can look much better or only modestly better depending on how biogenic carbon is treated, so the method should be stated whenever results are shared.
Real Examples
Common Misconceptions
People assume: Biogenic carbon makes wood buildings automatically carbon negative.
Actually: Stored carbon is released at end of life unless the wood is reused or kept out of decay, and the result depends on the accounting method and forest management, so such claims need care.
People assume: Biogenic and fossil carbon can simply be added together.
Actually: They behave differently in the atmosphere and standards report them separately, so combining them hides important assumptions.
Frequently Asked Questions
What is biogenic carbon?
It is carbon that was taken from the air by living plants and stored in their tissue, such as in timber. In carbon accounting it is tracked separately from fossil carbon, which comes from coal, oil, and gas.
How is biogenic carbon reported in EPDs?
Many EPDs list biogenic carbon in its own indicator or note, separate from fossil global warming potential, with uptake shown as negative and release at end of life shown as positive depending on scenario.
Is wood carbon neutral?
That depends on the accounting method and forest practice. Some methods treat it as neutral over time, and others emphasize timing and sourcing. It is not an automatic result.
Why does biogenic carbon matter for mass timber?
Timber stores biogenic carbon, which can improve a structure's apparent carbon performance, but the benefit depends on the method used and on end-of-life treatment.