Coalback Project : Exploring Wood Vaulting to reduce Wildfires Greenhouse Gas impact

As part of the Coalback project at ISTE University of Lausanne, which explores the potential for durable CO₂ removal through wood burial in former mines, L. Pipoz — under the supervision of M. Jaboyedoff — investigated an alternative approach to managing wildfire-damaged wood left in forests after fires. Wildfire-damaged wood is generally recovered and, where possible, valorised through conventional wood-processing pathways. However, the sudden availability of large volumes of damaged wood can put additional pressure on timber markets, while only a fraction of this biomass may ultimately be converted into long-lived wood products. This highlights the need to explore alternative pathways for managing and valorising this biomass. For this study, we focused on the Landes and Gironde regions in south-western France, where nearly 41,000 hectares of forest were affected by wildfires in late July 2026. The study explores whether underground wood storage, or Wood Vaulting, could provide an alternative pathway for this large volume of damaged biomass.

2026 Wildfires in France: Scale and Carbon Footprint
A focus on the Landes and Gironde departments

According to EFFIS satellite data, France’s 2026 wildfires emitted an estimated 5.09MtCO₂ by 19 August. The actual figure is likely higher, as satellite-based estimates do not account for carbon released through the combustion of belowground organic matter. But direct emissions from the fires are only part of the story. In late July, nearly 41,000 hectares of forest burned in Gironde and Landes, leaving around 3.5 million cubic meters of damaged wood — roughly 35% of the region’s annual production. That biomass stores 3.05MtCO₂, close to 40 % of the Gironde department’s annual greenhouse emissions (see calculations).

What happens to all this wood? Current situation

Damaged trees need to be removed to reduce safety and health risks. Fire-weakened pines are particularly vulnerable to bark beetles, which can multiply and spread to nearby healthy trees. Removal is therefore necessary from a forest-health standpoint, and the wood retains real economic value if it can be recovered.
Yet data from the Teste-de-Buch forest in Gironde after the 2022 fires suggests that only ~10% of recovered wood is turned into long-lived products (half-life ≥ 50 years), such as construction timber or flooring. The rest is therefore likely to release its carbon within years. These emissions add to the carbon footprint of the wildfires, while the sudden availability of large volumes of wood also puts pressure on timber markets.

An alternative: “Wood Vaulting”

As part of the Coalback project, we explored an alternative approach: underground wood storage, or Wood Vaulting. The principle is to bury wood under anoxic conditions, where the absence of oxygen greatly slows decomposition and can preserve the carbon contained in the wood for centuries. This method is inspired by natural coal formation and archaeological wood preservation.
Zeng et al. (2024) report carbon losses of under 5% in wood recovered after 3,775 years under comparable conditions.
It’s a promising emerging approach for carbon dioxide removal (CDR) from the atmosphere, but its effectiveness and feasibility have not yet been assessed at a large scale. Wood vaulting matters because durable CDR is needed at a massive scale: in IPCC scenarios consistent with limiting warming to 1.5°C, around 100–1000 GtCO₂ of CDR may be required by 2100, in addition to deep emissions reductions.

Could former mines provide the space?

Storing 3.5 million m³ of wood requires significant capacity. The Landes region happens to host several former lignite mining sites. One of them, Arjuzanx, is a flooded former mine located 120 km from the burned areas. Its main lake alone has a water volume of approximately 23 Mm³, compared with 3.5 Mm³ of damaged wood.
Under a scenario of truck transport to the site and according to our analysis, associated transport are estimated at 26-80ktCO2eq and would account for only 0.9-2.6% of the CO₂ potentially stored.

Assessment

This brief presents a desk-based feasibility assessment rather than an operational project. It suggests that the scale of the 2026 fires, combined with the availability of nearby former mining sites, could offer a rare opportunity to trial wood vaulting under real-world conditions — assessing logistics, costs, and emissions — while contributing to reducing the net carbon footprint of the fires themselves. With an estimated market value of €105–245 million for the timber and a potential carbon credit value of €540–840 million under a theoretical upper-bound scenario, this approach may also have economic relevance alongside its climate benefits. The carbon credit estimate is based on current high prices for carbon dioxide removal and assumes that 3 MtCO₂ can be durably stored. The actual value would depend on the amount of CO₂ effectively stored after accounting for emissions associated with transport, burial, and other operations involved in the storage process.

A full brief with further details is available for download below.

Bibliography

1. EFFIS, 19 August 2026
2. Vallet et al. (2025) Soil smoldering in temperate forests: a neglected contributor to fire carbon emissions revealed by atmospheric mixing ratios
3. HelloCarbo, “Incendies de forêt en France en 2026 : quel impact CO₂ ?” (2026)
4. Région Nouvelle-Aquitaine (2026), “Incendies en Gironde et dans les Landes : Les 14 mesures de la Région.”
5. Région Nouvelle-Aquitaine, “La filière forêt, bois et papier en Nouvelle-Aquitaine”
6. XyloDensMap (Leban et al., 2021), Fiche Pin maritime
7. Bert, D., & Danjon, F. (2006), Carbon concentration variations in the roots, stem and crown of mature Pinus pinaster
8. OREGES Nouvelle-Aquitaine / AREC Nouvelle-Aquitaine / Fiche départementale Gironde
9. Office National des Forêts, “La Teste-de-Buch : quatre ans après l’incendie, que devient la forêt“
10. Plan Comptable Forestier National (NFAP) de la France, Ministère de la Transition écologique (Réf : MPDOUV00264414)
11. Spear & Hart (2025), Modelling Wood Product Service Lives and Residence Times for Biogenic Carbon
12. Zeng (2008), Carbon sequestration via wood burial, Carbon Balance and Management.
13. IPCC (2018), Global Warming of 1.5°C, Summary for Policymakers, Section C.3.
14. Achigan.net, Lac d’Arjuzanx, Landes
15. Google Maps, route distance
16. FCBA, Écoconception des produits bois construction (Plan Bois IV), 2024.
17. Smart Freight Centre, GLEC Framework v3.2, 2025.
18. IFEU & SGKV, étude comparative transport route/rail-route, 2002.
19. Zeng & Hausmann (2022), Wood Vault: Remove Atmospheric CO₂ with Trees, Store Wood for Carbon Sequestration
20. Zeng et al. (2024), 3775-Year-Old Wood Burial Supports « Wood Vaulting » as a Durable Carbon Removal Method
21. : Centre National de la Propriété Forestière, Nouvelle-Aquitaine. (s. d.). Le prix des bois
22. CDR.fyi, 2024 Year in Review (2025)
23. XE. (2026). Currency Converter. Accessed August 26, 2026.

This work was conducted as part of the Coalback project within the Risk Group, ISTE, University of Lausanne.

Generative AI tools were used to assist with writing and create certain visual elements.