Inspired by how trees absorb carbon, a team from Nanjing University has built a “mechanical forest” powered by clean energy and designed to be cheap enough to scale.
This is the final story in our series spotlighting innovators supported by Tencent’s CarbonX Program—teams tackling some of the world’s toughest climate challenges and turning lab breakthroughs into real-world solutions.
Trees are nature’s carbon removal system. Through photosynthesis, they take CO₂ from the air and store the carbon in their trunks and roots. But when trees die and decompose, much of that carbon eventually returns to the atmosphere.
Professor Xiaojun Wang and his team at Nanjing University sought to build a mechanical version, powered by clean energy, that would store CO₂ permanently.
“If we can capture CO₂ like plants do,” he says, “but then stop it from going back into the air, then we achieve real carbon removal.”
Three elements, one system
The BioChargeDAC system developed by the Nanjing University team works much like a tree. Its “leaves” are made from biomass waste, which is turned into a material called charged biochar. It captures CO₂ as air passes through it. Clean energy — solar and geothermal — powers the process. A twin tower reactor uses heat to release the captured CO₂ from the biochar so it can be collected and stored.
What makes BioChargeDAC distinctive is that its material, energy supply and reactor were designed to work together as one integrated system, rather than developing them separately.
Low energy demand is the key
Capturing CO₂ demands energy. If the energy cost is too high, the economics collapse. BioChargeDAC’s biochar releases captured CO₂ at just 90–100°C, which keeps energy demand low enough for the system to work commercially.
“Low energy use is not just a nice-to-have, but the basic condition for making the technology viable in the real world,” says Professor Wang.
Taking root in Kenya
With the support from Tencent CarbonX 2.0, Nanjing University is working with world-class engineering and construction partners to deploy the system in Kenya — chosen for its solar resources, geothermal energy, local biomass supply, and geology suited to long-term CO₂ storage. Everything needed is in one place.
“Local communities don’t just receive climate solutions,” says Professor Wang. “They become active players in the global carbon removal effort.”
If the pilot succeeds, the goal is a standardized, replicable unit. A forest, not just a tree.
