1) We are not asexual
2) Population Explosion? Only in America. Take a look at Japan with their NEGATIVE GROWTH RATE (five hundred times more dangerous than an explosion)
3) China also, it is speculated, will be facing a negative growth rate at a dangerous rate, due to infanticide (especially female gendered babies, they go first), and an over-population of males. So I guess if you want to become a baby killer...sure.
4) The creation of Ethanol is very inefficient. First, corn shortages. Think of how much corn starch, for example, is used in syrups, candy, breads, and usually as a cheap substitute for most other consumed products needed to be thickened. Think of the average amount of corn consumed, including popcorn. Why would a farmer want to waste perfectly good, in demand crop, for a crude form of ethanol that uses more energy to create than how much the ethanol itself supplies? Well, you could subsidize the farmers, but in order for the government to get the money they will increase taxes. This decreases buyer power and confidence, causing us to go into a slight recession, which discourages even more. People start losing their jobs, and products become more expensive (because if no one is putting money into the products, who's going to pay for labor, or for resources? There will be a clear lack of capital)...its a downward spiral.
5) You're prolonging the inevitable by buying 'hybrid' products. BESIDES, do you know how much of an environmental hazard, and how expensive it is, to dispose of a hybrid car's battery? The only justified reason I see a hybrid, is in an SUV, just due to the base fuel efficiency being nonexistent. And you're car is made of plastic, guess how much of our valuable diminishing fossil fuel goes into that? And the rubber on cars! OH LORD! I will be dead before I am in a car made of anything but metal.
6) Also, as far as your Nitrogen illustration goes, my tank is 19 gallons, and my engine is 5 cylinder. Just wanted to throw that out there. Solar energy only would work in areas that would rarely if ever have an over cast. That's basically...Nevada. I have a few problems with Hydrogen I would like addressed. First, by stimulating extra water, wouldn't that cause the weather patterns to be completely messed up? The water's gotta evaporate somewhere. This could mess up anything from Hurricane patterns to crop seasons. Not to mention, it won't be very easy to phase in. You can't mix water and gas, and if the water is constantly evaporating off the street it will mix with fuel emissions (from older models, from people unable to buy new cars).
7) Will Steam engines work in the dead of winter in the middle of Chicago at all? It wouldn't matter if you can hit over 100 with it, either, as most driving I hope would be the speed limit. Honestly, the fastest I've gone is 85 mph. Most cars start to lose control at high speeds, and what is the 0-60 time? If it takes 20 seconds just to get fast enough to merge onto a highway, that become a serious danger. Not to mention, as with most of these other designs, in order to increase efficiency the car has to be very light, and thus not very safe. (hence the metal comment above.)
8) There's a fundamental problem with environmental headway, and that is developing countries. Something that typically hinders developing countries (such as several parts of Africa), is that other, larger countries, in order to progress their import/export power, will force technology onto these countries that have barely a sufficient monetary unit. Five times easier to deplete the resources and move on, since there is no one stepping in to say hold on, when no one in the country knows what's going on. Education on the matter in developing countries MUST improve before we can strive towards a green world, as, several countries are using 80s diesel trucks.
9) Aw what the hell! Of all the problems, you seem to have looked over Morimoto Disease...aka, Mercury Poisoning. Have you noticed, if you go fishing, that there might be signs telling you to eat no more than one fish a week? That's because mercury levels have increased to unsafe levels in natural bodies of level, due to improper waste disposal. This, is something I think everyone should look up.