QUOTE(Tony Watkins @ Sep 27 2006, 03:22 PM)

The industry has done an incredible job of cleaning vehicle emissions up, but I confess to being a bit surprised that the air coming out is cleaner. I accept everything you say - for a brand new vehicle. I don't keep up with car engineering developments like I used to, but don't 3-way catalysts for petrol engines have a relatively short useful life? I only know one person who has bothered getting a replacement cat - but as far as I know emissions are only checked annually on diesels in the UK so why should they? If all the modern cars driving around have steadily degrading catalysts, the situation is immeasurably better than it was, but there is still net pollution. And there are still significant numbers of older vehicles on the road - especially in developing nations. I wonder how many cars in a large Chinese city would be modern enough. My experience of India is that there were very few indeed. Then there's the problem that catalysts don't work at 100% efficiency because you can't make an engine run at stoichiometric all the time - or can you with clever engine management systems? Isn't it also the case that 3-way cats need to run hot - so don't work efficiently on cold engines. Mind you, I haven't noticed many whiff of sulphur dioxide from cold engines for a while. As I say, I don't keep up very well any more. Do cats clear up all the benzene emissions now? Last I heard, they reduced it by 50%. Still, fantastic progress is being made and continues to be made.
On the life of the 3-way cats, I haven't seen that data. I think that they must be pretty good for the first several years, to get past the annual Smog checks in states like California. But, your point stands; they dod degrade.
And, yes, you caught me fudging a bit on the Chinese city example. One of the main reasons a new car could clean the air like that is that all the old cars first put the pollutants there.
We do incredible amounts of computer modeling (for example, some people I work with use finite-element-based thermal analyses to design exhaust manifolds which will "light off" the cats more quickly). I think most modern catalytic converters reach steady-state performance in under a minute.
I'm sorry, I also don't know about the benzene.
QUOTE(Tony Watkins @ Sep 27 2006, 03:22 PM)

So, OK emissions is at least partly a red herring. But the problem of finite hydrocarbon resources certainly isn't. Developing clever ways of producing fuels from coal instead of crude can't be the final answer since the quantity is finite, however good we get at extraction from shales.
I think there is a lot more oil that we are not (yet) willing to drill for. But again, it's only a matter of time. So, once again, your point stands. I have heard some talks from ethanol and methanol proponents, but they haven't really satisfied me. The one thing that this problem has going for it is that the consumer is on the side of the engineers, in that we all want to drive. It's not the same for the catalytic converter, where (without government intervention) most would want everyone else to buy one, but not voluntarily spend money themselves. If I had to bet on a solution for 100 years out, it would be either electric battery vehicles or hydrogen fuel-cell vehicles with, in both cases, the potential energy ultimately having been produced at a nuclear plant.
QUOTE(Tony Watkins @ Sep 27 2006, 03:22 PM)

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I am strongly motivated to seek a solution which lies outside the cessation of recently popular human activities (such as driving automobiles).
Yes, but what? If it turns out to be the case that all this warming is purely natural (and as I've said, that's not what the consensus view of the evidence is), what could we do about it? We still only have control over human activities. Wouldn't it still mean drastically reducing greenhouse gases etc.? What else could we do? Actually, I heard a suggestion the other day. Since large volcanic eruptions put vast quantities of ash into the air which have been shown to reduce temperatures, couldn't aero engines be configured to spray volcanic ash into the air and weave us a blanket to reduce the intensity of solar radiation for a while?
I don't know either, but we need to start looking. I am enjoying your thought provoking questions, so thanks!