Graphyte — a US-based startup backed by Bill Gates’ Breakthrough Energy Ventures — is using old wood to store carbon underground, Bloomberg reports. The new tech, dubbed carbon casting, involves drying and sterilizing waste biomass like discarded wood residue — which naturally captures carbon — to prevent it from decomposing and releasing the captured CO2 into the atmosphere. The collected biomass is then condensed into carbon blocks and stored underground in an engineered storage site.

Carbon casting could compete with DAC: The startup says its cost of production is USD 100 per ton, which is much less costly than other carbon capture technologies like direct air capture (DAC). Graphyte plans to buy the waste biomass from local sources, and sell carbon removal services to corporations, Bloomberg writes.