Damnit, I had written a very long diatribe but got logged out and lost it.
Comparing diesel mpg and gas mpg straight up isn't entirely fair. To produce a gallon of diesel requires 17-25% more oil (depending on whether the gas is reformulated with MTBE or ethanol) and emits 17% more greenhouse gases. That is just production. And you pay for all of that oil, which is part of the reason why diesel gas is more expensive. So while burning a gallon of diesel emits fewer greenhouse gasses than does burning a gallon of gas, and diesel cars are more efficient, its basically a wash from an environmental standpoint when you consider production. PLUS, even the cleanest diesel engines still emit a ton more soot than gas. Its not even close. (Although, I have read that a couple of new diesel cars come close to meeting the tailpipe emissions of gas cars, but I don't know which ones.)
The California Air Resources Board has concluded that diesel soot is responsible for 70% of the state's risk of cancer from airborne toxics. In the population as a whole, studies have shown a 26% increase in mortality in people living in soot-polluted cities.
As far as hybrids go, its true that they have batteries that have toxic materials in them and use rare earth materials. But lithium batteries are so much less toxic than lead batteries this too is a wash. Plus, I know that Honda and Toyota both put stickers on their batteries offering something like a $200 reward if you recycle them. They claim to be able to recycle all parts with high efficiency. So, I doubt that the cars are any more toxic. However, increased use of rare earth materials is probably something to think twice about - especially considering China has a lockdown on rare earth resources.
And its also true that electric vehicles ultimately get their energy from some other source - gasoline, natural gas, coal, hydro-power, nuclear. But regardless of the production source, electrical plants are much more efficient at capturing that energy than is your car. Which is why it would cost about $1,200 a year in gas for a car getting 40mpg driving 15,000 miles while an electric car would only cost about $500 to "fuel" for the same distance. Of course, where that electricity comes from makes a difference. If your area uses coal fired power plants, you are probably generating more greenhouse gases than if you just used a gas car. But if you are in an area using nuclear power, greenhouse gases are not an issue (although there are potentially other environmental costs of nuclear power). In the US, with our patchy mix of electrical sources, you may or may not be helping out the environment. In some parts of Europe, with far greener electrical production, it probably is quite a bit 'greener'.
In all, I think diesel efficiencies are counteracted by the inefficiency of production. And the soot is not cool. Which is why 5 states ban the sale of diesel cars. Unless you are burning veggie oil, diesel is not any more environmentally friendly.
Electric vehicles are not quite there yet, but as their energy efficiency increases, and our electric grid becomes greener, they may be the way to go in the future.
Hybrid cars are not nearly as toxic as purported and represent a tangible way to turn a 20mpg SUV into a 30mpg SUV - which is a big difference in consumption over the life of the vehicle. And as things like regenerative braking become more efficient, and other innovative ways to turn motion into electricity are advanced, hybrids will become even more attractive.
For all you prius owners out there, you can add a solar panel to your roof for about $3,000 and make it go an extra 20 miles per day on just electric. And you know it will be clean electric.
http://www.wired.com/autopia/2008/12/the-solar-prius/
http://www.solarelectricalvehicles.com/products.shtml"The waves which dash on the shore are, one by one, broken; but yet the ocean conquers nevertheless."
- Lord Byron
