Jay,
I don't want to labour the point, but Nature figured out how to do that billions of years ago. And Nature does a cracking good job of it, in many different ways. We humans don't really have to add, or INVENT, anything, because we can get a lot further ahead than we are now, by just copying what Nature has already been doing for aeons.
I recall one proposal that involves some sort of "algae farms" out at sea. Not sure of all the details, but algae is basically "green slime" that can photosynthesize. There is much acreage of sunlight shining on the oceans, and I recall very reasonable numbers for megajoules-put-in-a-HC-bottle, per acre.
Another real-world example was Brazil in the 1970s after the first big OPEC "oil-shock". I recall Brazil being a bit miffed at the sudden increase in oil prices, so ... pretty much overnight they shifted their vehicle fuel economy to ethanol, which was derived from their then huge surplus of sugar-cane. Perhaps Daniel has better knowledge of the details, but I recall ethanol being well over half of the total fuel consumed. (Edit: But when oil prices dropped again, the use of ethanol also dropped. Daniel?)
And given the obesity problems in much of the Western world, shifting corn production in USA and elsewhere (which mainly goes to corn-syrup "sweeteners" for human consumption), to "food for the horses" would probably benefit everyone.
~o0o~
Yep, the Carbon-cycle is well proven. A real winner on this planet!The primary idea is that you could cease the extraction of hydrocarbons from the earth and simply recycle the carbons already in the atmosphere and then re-run them through the <strike>same kinds of combustion</strike> engines we have right now. Straightforward and very easy...
The problem is with the entrenched elements in our societies that profit from digging up those buried hydrocarbons.
Taking coal as an example (because there is enough of it for a long time yet), I reckon the coal-lobby are among the greatest supporters of the "Electric cars are the future!" ideology. As noted, the "free electricity from the sun" argument has two flaws, in that the solar-acreage needed either 1- competes directly with food production, or 2- it has to be sited so far away from where it is used that there are huge transmission costs and losses.
"BUT (!)", say the coal-lobby, "what if we build a brand-new, shiny power-plant, right next to the city? It is VERY SMALL in area, so it doesn't compete with the farms. And it produces CHEAP, CLEAN, ELECTRICITY, perfect for all the urban-greenies, who can drive their EMISSION FREE E-CARS all around town. And ... [note this now common argument->] any emissions from our combustion power-plants are much easier to treat at the single, central source, rather than from all those horrible little IC engines!"
Yep, E-cars sure are good news for the coal-industry.
(Of course, it is up to all you young people to use your "critical thinking" skills to determine whether "E-cars really are the future". Just because someone (Big-Coal, Claude?) says it is so, does NOT necessarily mean it is so.)
~o0o~
It is worth noting that the holy-grail of Hydrogen-power, "Whose only emission is PURE WATER!", has this same problem when used in IC-engine form.We just have to solve the issues with NOs that end up being emitted.
Any process that heats air up to a few thousand degrees C, such as happens in all common heat-engines, risks converting some of the N2 molecules into NOs. The solution, as has been thoroughly tested by all the past research into IC engines, is to get the gases hot enough to give good thermal efficiency (= Carnot-cycle, etc.), but not so hot that the N2s start breaking up. Apparently Nitrogen bonds are exceptionally strong, so high temps for good efficiency are still possible, just as long as you don't go too high.
But ... the better solution, IMO, is still to cut-out the middle-man. Do away with the conversion-to-heat-energy step in the middle.
Go from chemical-energy in HC+O2, DIRECTLY to mechanical-energy/work.
Big hint on how to do that in my first paragraph of this post.
Z