Yup it almost sounds like you're describing photosynthesis... take CO2 and add energy (sunlight) and we can make carbohydrates and other more useful compounds (like eventually petroleum). .Squeaky said:Apologies, I didn't read the article - just writing in response to the heading and some of the comments.
The notion of climate engineering has always scared me (at least the concept of injecting some sort of matter into the atmosphere for the purpose of global effect). Oh the hubris. I suppose you could argue: volcanoes do it, why can't we?
There are ways to use carbon dioxide extracted from the atmosphere (if you can get it without breaking the "energy" bank). I think it was perhaps George Olah that first championed the idea of converting atmospheric carbon dioxide to a fuel? He favoured what he called the methanol economy. Both methanol (MeOH) (a fuel and chemical intermediate) and dimethyl ether (DME) (a diesel substitute and chemical intermediate) can be produced from a mixture of carbon dioxide and hydrogen - a lot of hydrogen (CO2 + 3H2 = H2O + CH3OH). Both MeOH and DME are considered hydrogen carrier molecules. Electrolysis of water with nuclear power is probably an option for generating the H2 (if you want to avoid thermochemically converting carbonaceous material to generate the H2). I suppose you could equally argue that the above process (hydrogenation of CO2) is just as much a way of making water (molar equivalent produced). (Aside: In a real world process plant the water would be recycled for further electrolysis).
George Olah is a Nobel prize winner. Not sure if I have mentioned this before, but I recommend reading at least the first chapter of his book "The Methanol Economy". It gives an excellent high level overview of the earth's energy budget (for man to exploit). Puts things in perspective.
You could also use algae to remove CO2 - oils, vitamins and biomass are all useful products that could be generated. This sounds like a great idea until you look at the footprint required for an algae plant to remove the carbon dioxide from even a relatively small point source.
In any process that extracts CO2 for use, there is typically a huge parasitic energy cost associated with this extraction. It is difficult (energy intensive) enough at high concentrations of CO2 but becomes even more difficult at very low (ppm) levels of CO2. There are pushes for major technology development in this field (e.g. membrane technology). The energy cost of CO2 removal has been one of the down sides to power plants proposing sequestration.
The notion that there is some ideal level of atmospheric carbon dioxide would seem to be, in my humble opinion, absolute poppycock. I guess you could make a decent argument for a preferred range (we have limited knowledge or memory of the alternatives so this is challenging as well). Admittedly, the Holocene has largely been very pleasant for man, so from an anthropocentric position low to mid hundreds seems pretty nice. I do like plants and trees though (it is worth taking a look at carbon dioxide levels over geological time frames if you haven't yet).
I hope we don't see the end of the Holocene any time soon. I believe there is a push to bring in a new era, the "Anthropocene". Therein lies the rub, separating the man's influence from natural variation. Tough job. As a scientist I would be fearfully avoiding words like "certainty" and even "likelihood" when discussing model results. That is just me though.
Accurately (whatever that means) modelling a coupled, non-linear chaotic system seems to be a fool's errand. However, I've (mostly) preferred empirical data to simulations. Even hindcasting seems problematic enough (beyond relatively short-term tuning).
If a computer was developed to understand the above-mentioned system, then I might be more worried about the computer than anything else!
Sorry - got a bit off track towards the end.
Thanks for the thoughtful observations...
JR