There are many plans to extract CO2 directly from the air. Many people assure us it is necessary if we are to keep climate turmoil moderately stable, and avoid tipping points. However, as there is not that much CO2 in the air, you have to move vast quantities of air through the extraction plant, which requires heaps of energy, so you already have a problem.

The second problem is what do you do with the CO2?

Storage underground is unreliable – especially under the ocean or in old oil and gas wells (as the wells tend to fracture and crack releasing the CO2) and leakage has to be monitored and prevented for 100s of years, well beyond the life span of most companies or even governments.

Some solutions seem silly – after all in capitalism nothing is done, even something as obvious as save the world, unless it is compelled or makes a profit.

It has been proposed to use the CO2 to make the bubbles in soft drinks. Or to pump oil out of nearly dry wells, getting a substance that then produces more CO2.

Other people have suggested turning the CO2 into fuel and burning less oil or coal. The ‘and’ is important here, otherwise we are just adding to greenhouse gas emissions.

The problem with this last solution is the laws of thermodynamics. This process will have to use energy both to recover the CO2 and then turn it into fuel – more energy than will be gained by burning the fuel.

So the process can only be useful if we have lots of non-greenhouse gas making energy to spare, which we use to extract the CO2 from the air and manufacture the fuel. Our energy should likewise not be ecologically disruptive, and hydro for example certainly can be, as it floods some areas, dries up other areas, stops natural seasonal flows, stops aquatic creatures going upriver and so on.

The process is not impossible, but currently unlikely, at any level which makes the process useful.