Why does burning the product of Direct Air Capture not result in a net balance of CO2 in the air?


There’s been recent talk of a partnership between a DAC company and Big Oil, whereby the oil companies buy the waste produce from the DAC process off them, and use it similarly to biofuels.

Why does burning the product not just balance the processes out?

For anyone that’s not familiar: https://www.cnbc.com/2019/06/21/carbon-engineering-co2-capture-backed-by-bill-gates-oil-companies.html

In: Chemistry

I would think it does. But it gives you liquid fuel – useful for things like planes, I’d think?

It’s not ideal. Certainly not as good as just running DAC and *not* burning the result (though I doubt that would be commercially viable). That said, it’s still better than burning fossil fuels. In the case of DAC, CO2 is removed from the atmosphere (where it’s a problem) and then eventually returned to the atmosphere. In the case of oil, the carbon is removed from the ground, where it’s harmless to the environment, and turned into CO2 in the air, where it causes global warming/pollution.

Basically, burning fuel from DAC gives (approximately) a net zero change in atmospheric CO2. This is better than fossil fuels which create a net increase in atmospheric CO2 (on any time scale outside the geologic).

The comparison to biofuels is more interesting because they too have (theoretical) net zero CO2 emissions. I’m not an expert and it’s a new technology, but I’d assume that the advantage of DAC would be lesser land, water, and possibly energy requirements for the creation of the fuel than biofuel production.

So one of the interesting uses of high pressure CO2 is extracting oil from used oil fields. In the past some fields had done this with CO2 from nearby power plants, and it takes a lot of CO2 to displace a little bit of oil from the sponge like rock deep underground.

With a DAC plant you could acquire CO2 from the air (no nearby powerplant required) and wring more oil from the ground below. If I recall correctly, the amount of CO2 required is greater than the amount of CO2 produced by burning the oil. Thus this use for the CO2 is net negative.

All said this statement is based on years old memories of a discovery channel episode on the topic. If someone knows better please chime in.

Oh! The more you know