Steven Den Beste Just wrote an entry on a Californian law designed to reduce CO2 emissions. Now, far be it from me to contradict someone criticizing something Californian, for they truly are the fruit basket of the world (just kidding, for the humor impaired), but Steve is sidestepping some points that are important.
First off, I don't think that anyone really believes in battery-powered electric cars. A chemical battery's energy density is just far too low for that to work in the next few decades (if ever). Battery-powered cars are thus essentially a non-sequitor except when dealing with nitwits. The real plausible, short term alternatives to gasoline cars are fuel-cell cars and biodiesel cars (note: by short term, I mean one to a few decades).
The main problem with diesel is the operating characteristics of a diesel engine, and how different they are from a gasoline engine. The way that they are difficult to start in cold temperatures is the best example. However, whatever the viability of biodiesel, I really want to discuss fuel cell cars (much of what I'm going to say about fuel-cell cars will apply to biodiesel as well).
The first thing to point out about fuel cells is that hydrogen tanks are only one possible way to run a fuel-cell car, and they aren't necessarily the best anyway. There are fuel cells which can work well using hydrogen-rich fuels such as gasoline, or, more importantly, alcohol.
Now, alcohol is important for a number of reasons:
- Alcohol is made from plants
- Alcohol is easy to distribute and store with the same infrastructure as gasoline
- Alcohol has a high energy density (when not diluted with water), though not as high as gasoline
The 3rd point simply relates to how long one has to go between refills. I may be mistaken, but I have heard that a reasonably-sized alcohol-based fuel cell vehicle should be able to do 300-400 miles between refills.
The second point doesn't contradict what Steve said about fuel cells, except that alcohol is liquid at standard temperatures like gasoline and unlike hydrogen. Thus switching to alcohol-based vehicles will cost much less and be far less painful.
The first point is the really important one. The biggest benefit to using alcohol is that since it is made from plants, our enormous farming industry dovetails in quite nicely with the need for alcohol. It is currently acceptible to have very, very large farms and they don't cost nearly as much to operate as the mirror-covered-land hydrogen plants that Steve described. Moreover, if additional farms are needed, they don't cost nearly as much to build as the hydrogen generators. But most importantly, they already exist.
Even the industry necessary to turn farm-raised plants into alcohol already exists, though not in the size to produce the quantities that would be needed. Still, it is usually cheaper to grow a scalable industry than it is to create one. And as a nice benefit, farming is primarily solar powered (through photosynthesis) and would be virtually completely sow if farming equipment ran on biodiesel rather than oil diesel. (remember: this wouldn't be a perpetual motion machine because it is just a different means of using energy given to us by the sun, it would not be a closed system.)
The really relevant part about using alcohol as a primary fuel, however, has to do with CO2 emissions. Now, alcohol fuel cells would not signficantly decrease CO2 emissions. Fuel cells maybe be significantly more efficient (in theory, at least) than internal combustion engines, but not more than twice as efficient. However, the real question for global warming is not how much CO2 is put into the atmosphere in a given time period, but how much of it is actually there (it sounds like hair-splitting, I know, but it's an important hair).
CO2 in the atmosphere would be purely a function of how much is put there only if there was nothing taking CO2 out of the atmosphere. However, there is: plants. Plants take CO2 from the atmosphere and incoporate it into their body both during the synthesis of food as well as the process of growing.
When we put CO2 into the atmosphere, if the source is oil, we are taking carbon from vast underground stores and converting into atmospheric CO2, thus increasing the total CO2 in the atmosphere (since no new oil is being created and stored underground). However, when we get our CO2 from plants, we are taking CO2 which was very recently in the atmosphere and putting it back again. Thus, considered in the long term, if you raise 10^9 tons of plant matter every year and then burn it, the net change in atmospheric CO2 will be 0. If you burned enough oil to make the same amount of energy, you would be increasing the atmospheric CO2. Thus alcohol-based fuel cells, while not substantially reducing the emission of CO2, do substantially reduce the net CO2 change made by vehicles.
Now, of course, the Californian law is using the wrong techniques for trying to reduce the net atmospheric CO2 change. However, even though they got the method wrong, the fact still remains that by switching from gasoline to plant-based fuels, we can substantially and practically reduce the net affect on the atmosphere that we are having. If the Californian law were changed to reflect CO2 emissions by fuels which cause a net increase in atmospheric CO2, that would not be so unreasonable. That doesn't change the fact that they are passing laws demanding things without considering if what they want is actually possible, but what you do expect of Californians? :-)
Now, whether or not global warming is caused by man or by natural cycles, at least it would be quite feasible and not very expensive to try to remove contributions that we are making, however major or minor they might turn out to be. And if we don't have to suffer much to avoid taking the chance that we are screwing up the environment for ourselves, why not?
(As a side note, one nice thing about electrically driven cars is that if you include a bit of a battery, you can do things like regenerative breaking, increasing potential efficiency higher than what is possible with IC engines, at least in city driving. And fuel cells have a significantly higher theoretical efficiency, too (not to mention things like putting an electric motor on each wheel and thus avoiding the energy loss in axils and joints and such). Besides which, electric cars can produce quite a lot of torque more quietly for faster acceleration of less noise-poluting cars -- less money and energy spent on putting up concrete baracades next to highways.)
Update: It has been claimed that ethanol production is energy negative, i.e. that it takes more energy to create ethanol than you get from producing it. I did some research and discovered that this does not appear to be true in general. More on this below. However, even if it is the case, I don't believe that anyone thinks that biodiesel (vegetable oil) is energy-negative. Most reports that I saw when searching claimed that it was very energy-positive. And most of the energy taken up in making ethanol (which is likely to be reduced as better enzymes are developed to make the process more efficient) are in powering farm equipment and heating the fermentation chamber. Both of these could be done using biodiesel, and thus ethanol, even if energy-negative by itself, would still be CO2-neutral and a decent storage medium for energy in a renewable way. Even if the biodiesel were not the case, it would still very substantially prolong the use of the oil reserves we do have now.
As I mentioned, I did some research and found the following. I wanted things that said energy-positive, though I searched google for "postive OR negative", and wasn't consciously trying to bias the outcome. Even so, do not take the disproportionate number of citations to be truly representative of expert opinion. I'm just posting these to save you some time doing your own research. Don't let this be the only stuff you look for.
- Estimating the Net Energy Balance of Corn Ethanol (this one is by the United States Department of Agriculture, which I believe we can all consider to be at least relatively impartial).
- How Much Energy Does It Take to Make a Gallon of Ethanol?
- Biomass Resources for Energy and Industry
- Green Fuel Challenge
- Ethanol and the Environment (the site in general, Renewable Fuels Association, is interesting).
- Ethanol: Separating Fact from Fiction (but it has pictures of people being happy because of ethanol, so I am suspicious of it.)
- Renewable Energy: Economic and Environmental Issues (though it isn't clear that biomass in general can't be energy positive if you use vegetable oils (which are very energy positive) to power the ethanol creation process, and it wasn't clear about whether or not methanol is energy negative.)
And note: I never mentioned that the alcohol in question had to be ethanol coming from corn. Other types of alcohol are more efficient (methanol, though more dangerous, is more efficient and other plants are better than corn for making ethanol).