Biogenic carbon in wood products
Wood absorbs CO₂ as it grows and stores the carbon in the material. This article covers EN 16449:2014, the standard specifically for calculating how much biogenic carbon (and its CO₂ equivalent) is present in a wood or wood based product, such as timber, glulam, CLT or particleboard. The result is a material property at the factory gate, not a prediction of end of life outcomes.
The formula
Variable | Description | Default / unit |
P(CO₂) | CO₂ sequestered in the product | kg CO₂(output) |
cf | Carbon fraction of woody biomass, oven dry basis | 0.50 (default) |
ω | Moisture content, wet basis | 12% (default) |
ρω | Density at moisture content ω | kg/m³ (species specific) |
Vω | Volume of solid wood at moisture content ω | m³ (input) |
44/12 is the molecular weight ratio of CO₂ to carbon: each kg of stored carbon equals 3.667 kg of CO₂.
The carbon fraction of 0.5 holds well across species, since wood's elemental composition is stable at roughly 50% carbon by weight. Both defaults (cf = 0.5, w = 12%) are accepted for most declarations unless you have evidence for a different value.
Composite products: adjusting for wood content
If your product is glulam, CLT, particleboard, OSB or another engineered wood product, it includes adhesives or resins that carry no biogenic carbon. Using the gross product volume in that case overstates the result by the full binder share, typically 5 to 15%.
If that applies to your product, reduce the volume term to the wood fraction first, using this formula:
Product | Typical wood content |
Solid sawn timber | 100% |
Glulam | ~90% |
CLT | ~92% |
Particleboard | ~85% |
OSB | ~85 to 90% |
Verify the actual wood content against the manufacturer's declared composition (EN 16485); the table above is only a sanity check.
Worked example: CLT panel, 1 m3 gross volume
Parameter | Value |
Gross volume | 1 m³ |
Wood content | 92% |
Effective wood volume | 1 x 0.92 = 0.92 m³ |
Density | 470 kg/m³ |
Moisture content | 12% |
Carbon fraction | 0.50 |
Oven dry mass = (470 x 0.92) / 1.12 = 386 kg
Biogenic carbon = 0.5 x 386 = 193 kg C
CO₂ sequestered = 3.667 x 193 = 708 kg CO₂
This falls within the expected range for CLT below, a useful check before publishing any result.
Sanity check ranges
Product type | Typical CO₂ range |
Solid softwood | 900 to 1,100 kg CO₂/m³ |
Solid hardwood | 1,200 to 1,600 kg CO₂/m³ |
Glulam | 850 to 1,050 kg CO₂/m³ |
CLT | 880 to 1,080 kg CO₂/m³ |
Particleboard | 750 to 950 kg CO₂/m³ |
Hardwoods score higher purely because they are denser; the carbon fraction is the same 0.5 for every species. A result well outside these ranges usually points to an input error, most often the moisture basis or using gross volume instead of effective wood volume.
Common errors
Manufacturing waste is excluded. The formula applies to the finished product leaving the factory gate, not the raw material consumed to make it.
Reused wood content is not deducted here. It is physically present, so it counts in full. It is only deducted later from GWP biogenic, a separate calculation.
Moisture content must be entered on a wet basis, consistent with the (1 + ω/100) denominator. Mixing up wet and dry basis can shift the result by 10 to 15% while still looking plausible.
Multi species or multi product declarations should be calculated per product and summed, not averaged.
Using the calculator
The calculator is attached at the bottom of this article.
Open the Calculator sheet.
Enter the blue input cells: gross volume, declared mass, wood content %, moisture content.
Override the default carbon fraction only if you have a justified reason.
Results calculate automatically. The main result is the "CO₂ sequestered P_CO₂"
For several products in one declaration, use the Multi Product sheet instead; enter one product per row and totals sum automatically.
Blue cells are inputs, green cells are calculated, yellow cells are defaults you can override.
If you have questions about applying this to your own product data, reach out to our support team.