CCS Applications
Indirect Air Capture (iDAC)
Addressing Climate Change Through Green Wastes
Climate change is arguably the most significant challenge facing humanity in the 21st century and OHD may have an important role to play in our response.
The IPCC has made it clear – we can’t reduce CO2 emissions enough to avoid the worst effects of climate, we also need to recapture CO2 that’ we’ve already released. But recapturing CO2 and sequestering it so it can’t return to the atmosphere, is hard. Very hard. We need to capture a dilute gas and convert it to a concentrated fluid (or solid), and everything about that takes energy. The more dilute the gas, the more energy it takes, and atmospheric CO2 is very dilute – 0.04%.
The Laws of Thermodynamics can’t be overcome with efficiencies, catalysts, or anything else. Those energy costs must be paid. But that doesn’t mean that we have to pay them!
Photosynthesis is the most effective natural process for capturing CO2 from the atmosphere! Plants continually take up CO2 and convert it to biomass. After roughly 3 billion years of evolution to work out the kinks, nature has this problem pretty much solved. One pound of raw biomass contains about the same amount of carbon as one million liters of air, pre-captured and pre-concentrated, and all the energy required to accomplish that came directly from the sun.
OHD can effectively convert biomass and biomass-derived wastes to an aqueous solution that retains about 90% of the original carbon. That solution can easily be injected into depleted oil or gas reservoirs, deep saline aquifers and other geologic storage sites where there is no chance of contaminating surface or near-surface ground water that might affect humans or the environment, and where the carbon it contains will be sequestered for eons.
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.
Humans are already producing vast amounts of biomass that provides everything we need to tackle climate change. We grow it to produce the food we need to feed ourselves; we grow it for fibers and oil, and for a host of other purposes. Agriculture is essentially industrialized photosynthesis, so it’s also essentially industrialized carbon capture. All we need to do is take advantage of nature. Our farmers can be the ones that save us (again). Anything that’s derived from anything that was grown anytime since the industrial revolution will work. There’s no need to grow specialty crops and absolutely no need to harvest ecologically important natural environments. Simply grow the food and all the other products that are made from things we grow and use what we need - just as we do now. Then, once we’re finished with them, instead of letting the wastes decompose and re-release their carbon back into the atmosphere as CO2 or methane, break them down with OHD and store the carbon deep underground.
Indirect air capture. Simple, scalable, and working with natural processes rather than against them.