UNDERGROUND FOREST
CarbonFix cohort
Type
Founders
Type of impact
Type of invention
Key Milestones
Current TRL: 8
TRL 9: 2025
First 1Mt CO2e Captured: 2028
CO2e p.a. in 2030: 2-5 Mt
About this project
Founded by Kees de Gruiter in 2023, Underground Forest revives ancient wood-piling techniques for long-term carbon storage. Using sustainably sourced logs, they aim to store CO₂ for up to 1,000 years while offering solutions for peatland restoration and climate-neutral housing. With support from CarbonFix, the venture is preparing to sequester its first kiloton of CO₂ by 2025. Their versatile and nature-based approach provides a scalable, sustainable way to combat climate change while minimizing re-emissions.
Founder Q & A
Read our full interview with Kees de Gruiter here.
Q: Should we be cutting down trees just to bury them?
People don’t realise that all the CO2 a tree has sequestered during its lifetime returns to the atmosphere when that tree falls to the forest floor. A wild, unmanaged forest becomes mature in about 50 years and reaches a peak of around 500 tons of CO2 stored per hectare above ground. After that, about 2 percent of the stored carbon is released annually through natural decay and fire, so the forest transitions from being a carbon sink to being carbon neutral.
If you instead manage the forest and harvest 2 percent of it per year, then the amount of carbon sequestered by the trees is the same, and the carbon captured in the harvest can also be preserved instead of released back to the atmosphere. That means that managed forests remove twice as much carbon over 50 years compared to wild forests.
If you use harvested wood to make paper or pulp or burn it in a power plant, all the CO2 is released again within a year. If you use it for building materials, it may last 50-100 years. There is enough wood in the forests to harvest sustainably for wooden buildings on wooden foundations. So we should do both: keep our forests, and build with wood.
But the optimum way to really store that carbon permanently is to bury the wood in anoxic peat and clay. There is no method of forest management that removes more carbon than the Underground Forest method.