This forum is about wrong numbers in science, politics and the media. It respects good science and good English.
So this is equivalent to burning the natural gas (or indeed petrol) to get your power and saving the CO2 at the exhaust pipe, or chimney. Can CO2 be got out of exhaust gas more easily than the macro-economic impact of changing to hydrogen delivery/storage before we can use an H2 car? And IF we could do it by CO2 sequestration at the pipe, how is that different from gathering pre-sequestered CO2 (vegetable matter that's about to rot) and dropping it in the deep ocean where it's too cold to rot and the pressure won't let CO2 release anyway?
I was assuming that steam reforming and any other process based on conversion of a fossil fuel would be unattractive. Apart from the fossil fuel running out problem its easier just to collect the natural gas, split it into components and burn it direct rather than faff about with the hydrogen conversion process. Anyway there are significant costs involved in the collection of the gas feed-stock whether by conventional drilling or some form of bio-conversion.
This basically leaves electrolysis or some form of electrically powered catalytic process for getting the hydrogen so the query is can some such process be used to split the carbon dioxide. If so is it then feasible to react carbon and hydrogen to produce convenient liquid fuels and replicate petrochemical feed-stocks for all the processes and products such as lubrication, plastics and so on. Nuclear power, presumably via the thorium (?) breeder cycle (my atomic physics is very rusty) is the only near horizon viable power source. Obviously the power plant and associated conversion units will be expensive and the overall energy conversions pretty lossy too. However collecting the water and carbon dioxide feed-stocks is simple pumping unlike conventional petrochemical extraction and refining which involves a lot of expensive plant needing oodles of power to drive it.
I suspect that a proper analysis of the input to output energy losses in the current industrial petrochemical process would be depressingly bad.
Eveything about hydrogen seems to me to be unattractive, except that it can be used as fuel with no unwanted emissions at point of use. As a motor fuel though, it takes far more space per unit output than petrol, is hard to store, and the infrastructure to use it doesn't exist. All the refineries and stuff for petrol already exist and are paid for. IF we could get the CO2 out (and any other thing the luddites decide is bad too) of the exhaust, wouldn't the car as currently used be better in every way? And IF sequestering the same CO2 elsewhere than the exhaust is possible, wouldn't that be the same, in terms of end result? The main problem here is that some groups really really want to get rid of the car, and all forms of personal mobility, and any proposal leaving the car unfettered is no good to them. Single-issue groups cannot be appeased by concessions. For the greenies, solutions which do NOT involve regression are not acceptable.
I am totally in favour of seeing the total energy end-to-end figures for all these alternatives, but where can they be found, and if found, are they free from 'interpretation'?
Back in the 1990s Toshiba were supposed to be on the verge of developing some ceramic material that was an efficient CO2 absorber and could potentially be used in vehicle exhausts. The CO2 could be released by later heating up the ceramic material. I did a Google search and managed to find the 1999 press release:
But I haven't heard anything about what happened to this research work since.
There's a lot of it you know, something like three times the mass of petrol used. Drive thirty miles and you've got 6-10 kg of the stuff to get rid of. No way that could be stored in a small amount of ceramic or anything. Drive to your 300 mile refuelling range and the amount weighs as much as a passenger.
(all amounts correct only to order of magnitude!)
It seems ever clearer to me that the 'greenies' collectively, no matter which wing of greenism they stand for, are all saying the one trunk or four legs good (unless it's a industrial farm animal) and two legs bad (unless it also has wings or a tail.)
So the key is to reduce the population of the world. To nothing if possible if some of them are to be taken at their word.
Now it occurs to me that they believe that Humanity is doing just that already so I suppose their main concern must be for the plants and the creatures (4 or more legs or with wings or tails) that rely upon them. Otherwise they would be encouraging all those things they discourage since they must believe they will create ever faster changes leading to the destruction of the planet as it currently exists.
On the other hand one could suggest that the only purpose of humankind is to correct the damaging loss of plant life giving carbon when so much of it was sequestered, presumably accidentally, at some point before recorded history began.
Clearly humanity was created specifically to correct this accident and, having taken a while to work out how, may now be in a position to deliver a complete solution and return the planet to the verdancy and temperatures it must have enjoyed when the dinosaurs were around.
I can't imagine why tree lovers would wish to eliminate such activity. Especially since once the CO2 has been liberated there would be no need for humanity ust at the point where humanity might well have no viability. Perfect synergy!
As for hydrogen - a touch of the vapours surely? Would there really be no effect on anything from the H2O exiting the tailpipe?
(going mad just like all the others, but possibly in a different direction ...)
As water vapour is, in general, not a well mixed "gas" a pure hydrogen fuel will bump up the levels of water vapour in the air quite nicely in populated and urban areas. Urban heat island effect will get worse. Water vapour is a more effective greenhouse gas than carbon dioxide and pure hydrogen is a less effective fuel than liquid hydrocarbon there will be more greenhouse effect emissions per horsepower produced.
Another fine example of the law of unintended consequences.
Now if a system for extracting hydrogen from water and carbon from atmospheric carbon dioxide to make liquid hydrocarbon fuel could be developed everything pretty much stabilises. Carbon from exhaust carbon dioxide released the atmosphere is recycled into fuel, water vapour from the exhaust recycles as rain in the usual way. Hence any variation is simply linked to number of hydrocarbon engines in use, their mean efficiency, mean power output and mean run time. There is no continuous accumulation.
And if you want to reduce atmospheric carbon dioxide extending the process to produce feed-stock for plastic materials might actually provide some sort of economic return. Have more chance than pumping the stuff into caves.
Of course this sort of thing will increase the oxygen content of the atmosphere but, as far as les greens are concerned, oxygen is perfectly safe and a bit more makes no difference.