# Definitions Biogenic carbon is the elemental carbon stored in bio-based materials. This biogenic carbon is often converted to a $CO_2$ equivalence. Biogenic carbon can be classified in two ways, as outlined by the [[Prestandard for Assessing the Embodied Carbon of Structural Systems for Buildings]]: ***Biogenic Carbon Content:*** *the carbon content of biobased building materials, estimated as approximately 50% elemental carbon by dry mass. Although this carbon is stored within the material, it is not necessarily considered a benefit or negative credit to the material’s net embodied carbon impact and is independent from the life cycle stages.*  ***Biogenic Carbon Flow:*** *the quantifiable flow of biogenic carbon content entering or leaving the system boundary within building materials across each lifecycle module. The flow considers the biogenic carbon content entering and leaving the system boundary, using a static -1/+1 $kgCO_2e/kgCO_2$ characterization method, in conformance with ISO 21930:2017.* # Biogenic Carbon Content The biogenic carbon content of a wood product can be calculated as: $C_{bio}=(-1)∗C∗M∗(1-\frac{MC}{100})∗\frac{44}{12}$ where, $C_{bio}$ = Biogenic carbon content $(kgCO_2)$ $C$ = Biogenic carbon per unit mass of biobased material $kgC/kg$, (0.5 kgC/kg for harvested wood products) $M$ = Mass of biobased material within the assessment scope $(kg)$ $MC$ = Moisture content of biobased material  (%) Biogenic carbon content can be thought of as the carbon that is stored in the wood product. The carbon that the building is responsible for keeping out of the atmosphere. This metric does not have any implications for climate change, rather it is a measure of the elemental carbon in a building. # Biogenic Carbon Flows Biogenic carbon flows represent the flow of biogenic carbon between system boundaries. ISO 21930 defines that a credit ( $-1kgCO_2e/kgCO_2$) is given for biogenic carbon that enters the system boundary, and then an emission ($+1kgCO_2e/kgCO_2$) for biogenic carbon that leaves the system boundary. This method of accounting for biogenic carbon is well recognized by the LCA community and implemented in most LCA tools. Dynamic LCA is another approach for a more nuanced approach to accounting for the temporal affects of forest regrowth. [Hawkins et al. 2021](https://www.sciencedirect.com/science/article/abs/pii/S2352012420307323) shares an example of using dyanmic LCA to compare structural systems that contain biogenic carbon. # Biogenic Carbon in LCA Tools As part of a 4-part series, Woodworks has put together a review of how biogenic carbon is treated in LCA tools: [Biogenic Carbon Accounting in WBLCA Tools](https://www.woodworks.org/resources/biogenic-carbon-accounting-in-wblca-tools/). Other articles in the Woodworks series includes: - Part 1: [When to Include Biogenic Carbon in an LCA](https://www.woodworks.org/resources/when-to-include-biogenic-carbon-in-an-lca/) - Part 2: [How to Include Biogenic Carbon in an LCA](https://www.woodworks.org/resources/how-to-include-biogenic-carbon-in-an-lca/) - Part 3: [Biogenic Carbon Accounting in WBLCA Tools](https://www.woodworks.org/resources/biogenic-carbon-accounting-in-wblca-tools/). - Part 4: [Long-Term Biogenic Carbon Storage](https://www.woodworks.org/resources/long-term-biogenic-carbon-storage/) # Navigation Return: [[Home]] Suggested Next: [[How to Calculate Embodied Carbon (IStructE)]]