Another idea would be to look into biodiesel - diesels do better than regulars on mpg, plus biodiesel is renewable, contains no petrol, and has lower emissions in every category but one. The problem here is that the media treats it as a freak show rather than the viable commercial fuel that it is.

You could evaluate production costs and capabilities, compare the benefits and economic adjustments required to accomodate widespread biodiesel production and usage and see if its really feasible as a large scale alternative to petrol diesel. Naysayers typically point out that we can't produce enough biodiesel to support all our diesel needs. This may be true or not, let's find out first. Also we need to decide if that even matters - replacing any percentage of our petrol diesel usage with a renewable alternative that burns cleaner is a good thing whether we can to a 100% changeover or not.

There's lots of politics in this too that are interesting. The soybean farmers lobby is pushing biodiesel, but soybean biodiesel in particular. Trouble with that is that there are much more efficient crops to make biodiesel out of that are getting ignored because of the power of the soybean lobby. So, while they're trying to do good for themselves they're not really helping the widespread use of biodiesel because they're trying to monopolize on its production when other crops like algae are much better sources of the raw materials.

Other politics involve state requirements on biodiesel percentage mixed in with petro diesel at the pump. this is a great idea, but in minnesota for example, they exempted the railroads and mining companies from the requirement. This basically made the law useless as those are the two largest diesel consumers in the state. So if they're not going to have the balls to enforce the rule where it can really make a difference, then why bother? I guess it still makes a difference but not where it counts the most.

All interesting stuff to research. Good luck.