Too much, or not enough?

A109 Light Utility Helicopter flight with mayor Gisborne City from the air in November 2023.

Opinion

Isn’t it ironic that there’s too much carbon dioxide (CO2) in the atmosphere and not enough to put into fizzy drinks?

When we say “too much” in the atmosphere, it’s actually not a lot; only around 400 parts per million by volume (0.04 percent) or 600ppm (0.06 percent) by weight; you wouldn’t think that small amount would have much effect, but scientists assure us that it does.

The other day I was thinking about the CO2 created by the ever-growing number of planes in our skies, gobbling up tonnes of jet fuel every second of every day and dumping the exhaust just where we don’t want it, in the stratosphere. I thought “This has got to be a major contributor to global warming.” So I did some sums:

Global consumption of aircraft fuel is around 250 MegaTonnes per year and this produces around 750MT of CO2. The total weight of CO2 already in the atmosphere is calculated by taking 0.06 percent of the total weight of the atmosphere, which is obtained by multiplying the surface area of the earth, in square metres, by atmospheric pressure at ground level (because this represents the weight of air piled on each square metre of surface). Are you still with me?

Anyway, it turns out that the total weight of CO2 already in the atmosphere is 3 million MT. Now, say, that’s not a lot! However, by comparison, the 750MT from jet fuel pales into insignificance — it adds just 0.1ppm per year to the current level of 400ppm. So, that’s that myth busted!

Now, on to the question of where the CO2 for fizzy drinks comes from . . .

Despite the gi-normous amount of CO2 in the atmosphere, it is so dilute that it does not make sense to try to collect it for use in fizzy drinks.

Technology exists for “sequestrating” (capturing) CO2 from waste streams (eg flue gases) but, again, it is generally too dilute to be commercially viable as it comprises 80 percent nitrogen from the combustion air. Rather, CO2 is generally “harvested” from processes that create a rich stream, such as the production of lime from chalk (CaCO3 gives CaO plus CO2). How else might we produce a rich stream and solve another problem at the same time?

Well — what resources do we have here in NZ? We have an abundance of rubbish (rich in carbon) and lots of renewable energy which we could use to extract oxygen from the air. Carbonaceous material burnt in oxygen produces such a rich stream. A recent correspondent to this newspaper rightly decried incineration of forestry wastes, but it seems to me that incineration of domestic rubbish using oxygen rather than air, and sequestration of the resultant CO2 for carbonating soft drinks, actually solves several problems in one go. How about it, boffins?! Could NZ be at the forefront of new business ventures, designing and building oxygen-rich incineration and sequestration plants (INCAS)?

Finally, to those who have made it to the end of these ramblings and spotted the snag, that it will add even more CO2 to the atmosphere — I think you’ll find that, like jet fuel, the impact would be negligible. But I’ll leave others to do those sums!