We call it Indirect Air Capture, or iDAC for short. The net effect is the same as other so-called direct air capture (DAC) methods: Carbon is captured from the atmosphere and sequestered deep underground, where it originally came from, and where can’t escape back to the atmosphere again.
iDAC has many advantages compared to conventional DAC methods:
- Its technologically simple and inexpensive.
- It uses only heat, water and oxygen, so there are no expensive or dangerous chemicals involved.
- The flexibility of the OHD process means that it can be configured to intake almost any form of biomass or biomass-derived wastes, including agricultural and forest wastes, kitchen and garden wastes, paper, and cardboard; even manure and sewage will work!
- The process can be configured to accommodate a wide variety of local circumstances and scales.
- And, perhaps most importantly, the captured carbon isn’t stored as CO2, it’s stored as organic carbon.
Storing CO2 is hard. It constantly wants to expand to a gas and escape again. It needs to be stored very deep underground where the pressures are high enough to keep it as a fluid, and complex monitoring and verification systems are needed to make sure it’s not leaking back to the surface again. That’s why CO2 storage sites require very complex permitting (so-called class VI injection permits in the USA). But OHD liquor is an aqueous solution of organic carbon. It simply mixes with the fluids that are already present in the subsurface (usually salty water). Like spilling iced tea into a swimming pool, it simply mixes with the fluid that’s already there and there’s nothing driving it to try to escape again. Industry all over the world has many decades of experience injecting aqueous fluids into the deep subsurface, and the permitting process (for Class I and Class II injection wells) is well established and much less onerous.
Storing captured carbon in organic form also means that once it’s injected into the subsurface, rather than suffocating the microbes that exist there, it will feed them. There are lots of microbes in the subsurface, in fact it’s sometimes referred to as the “deep biosphere”, and we’ve shown in the lab that they thrive on OHD liquor. They take up the organic carbon in the liquor and use it to drive their own metabolisms. In essence, they eat it. So once they get it, they hang on to it and recycle it, which helps to ensure that once the carbon is sequestered, it stays sequestered, for a very long time.