Carbon-Negative
Building Materials
THS v1.0 - Annex L
Carbon-Negative Building Materials engineers bio-based feedstocks - fast-growing wood, hemp hurd, fungal mycelium, straw - into structural or non-structural building products that embed more atmospheric carbon than was emitted across their full production lifecycle. Unlike conventional carbon-intensive materials such as steel and cement, well-designed bio-based products can serve as long-term carbon stores within the built environment itself, while meeting the performance requirements of modern construction.
How this pathway works
Plants draw down atmospheric CO₂ as they grow, incorporating carbon into their woody or fibrous tissue. When that biomass is engineered into structural or building envelope products - mass timber, hempcrete, mycelium-based insulation panels, or compressed straw panels - and installed in a building with a multi-decade service life, the embedded carbon remains locked away for the duration of that service life, effectively turning the building itself into a long-term carbon store. This stands in direct contrast to steel and cement, whose production is a net carbon source.
Under the Teravent Hybrid Carbon Standard (THS v1.0) Annex L, this pathway is classified as hybrid because durable crediting requires accounting for both the biological carbon uptake of the source material and the engineered manufacturing process that converts raw biomass into a verified, service-life-documented building product. Teravent Hybrid Credits (THC) are issued for verified net tonnes of CO₂-equivalent embedded in the finished building product, net of full lifecycle production and manufacturing emissions.
THS v1.0 - Annex L
This pathway is governed exclusively by the Teravent Hybrid Carbon Standard (THS v1.0). No external registry, standard, or methodology is referenced or incorporated.
Four approved methodology variants
THS v1.0 Annex L approves four methodology types, differentiated by feedstock and product category.
Cross-laminated timber (CLT), glued laminated timber (glulam), and other engineered wood products are manufactured from sustainably sourced sawn lumber, laminated and pressed into structural panels or beams capable of substituting for steel or concrete in mid-rise and increasingly high-rise construction. The engineering process itself adds relatively modest embodied emissions to the underlying wood's already-sequestered carbon, provided the sourcing forest is independently certified as sustainably managed.
- Sustainable forestry certification documentation confirming feedstock sourcing chain
- Embodied carbon per unit product, verified through material composition analysis and manufacturing process energy tracking
- Structural engineering service-life assessment for the specific building application
- Product distribution and end-of-life disposition tracking
Hempcrete combines the woody core (hurd) of the hemp plant with a lime-based binder to form a lightweight, insulating wall infill material that, notably, continues absorbing atmospheric CO₂ through lime carbonation for years after installation, in addition to the biogenic carbon already embedded in the hemp fibre itself. Hemp's rapid growth cycle (typically under four months to harvest) supports high feedstock turnover relative to timber.
- Hemp hurd feedstock sourcing and growth cycle documentation
- Lime binder ratio and post-installation carbonation rate, verified via material sampling where feasible
- Building envelope service-life assessment for the specific application
- Embodied carbon per unit volume installed
Fungal mycelium is cultivated through a substrate of agricultural residue (straw, hemp hurd, or similar), binding the loose fibrous material into a solid composite as the fungus grows, then heat-treated to halt growth and stabilise the finished panel. The resulting material serves as a lightweight insulation or non-structural panel product, sequestering the carbon of both the substrate and the mycelium biomass itself, produced from waste agricultural material with minimal processing energy relative to conventional insulation manufacturing.
- Substrate feedstock sourcing and counterfactual fate documentation
- Mycelium growth cycle and heat treatment records confirming stabilisation
- Independent engineering service-life assessment for the specific building application
- Worker exposure monitoring for fungal material handling
Wheat, rice, or other cereal crop straw - an agricultural residue typically left in field, baled for animal bedding, or burned - is compressed under high pressure and heat into dense structural panels, in some formulations using the straw's own natural lignin as a binder rather than synthetic adhesives. This methodology puts an existing waste stream to durable structural use with minimal additional processing inputs.
- Straw feedstock sourcing and documented counterfactual fate (field burning, animal bedding, landfill)
- Compression process energy and binder content per batch
- Independent engineering service-life assessment for the specific application
- Product distribution and end-of-life disposition tracking
Which emission sources must be counted
Measurement, reporting
& verification
Embodied carbon per unit product is quantified through material composition analysis and manufacturing process energy tracking, following a lifecycle assessment methodology consistent with established embodied carbon accounting standards (e.g. EN 15804-aligned product category rules). Service life is documented through an independent engineering assessment specific to the product's structural or envelope application, with a minimum 50-year design life required for Class II crediting.
Demonstrating additionality
Leakage types & deductions
Buffer pool & NPRR assessment
| Methodology | NPRR Rating | Buffer Pool Rate | Primary Reversal Risks |
|---|---|---|---|
| CBM-M01 Mass Timber | Very Low | 7–15% | Premature demolition; fire (structural, well-documented safety margins) |
| CBM-M02 Hempcrete | Low | 7–20% | Building envelope replacement ahead of design life |
| CBM-M03 Mycelium Composite | Medium | 10–22% | Less established long-term performance data; early TRL |
| CBM-M04 Compressed Straw | Low | 7–20% | Moisture exposure risk if envelope detailing fails |
Key registration criteria
Sustainable Development
Goal alignment
Deployment scope: Global - regions with established forestry, hemp, or agricultural residue supply chains and growing mass timber or bio-based construction markets, currently concentrated in Northern Europe, North America, and parts of East Asia.
Ready to register your
building materials project?
Submit a Project Concept Note under THS v1.0 Annex L to begin your registration. Select the CBM-M code matching your material, commission an independent service-life assessment, and appoint an accredited VVB to validate your PDD.