Trucks use diesel fuel because the density of diesel and its subsequent power output is greater than gasoline. In a nutshell, a diesel engine is better suited to "hauling" heavy loads.
Ethanol doesn't really do anything for diesel trucks and cars. Ethanol is also driving fuel prices up as food crops are diverted to make energy. And, diesel fuel is going through the roof because there haven't been any cheaper alternatives, like ethanol, that can be mixed with it to somewhat keep costs down. But, now there is hope in a toxic, non-food, drought-tolerant plant called jatropha.
Jatrapha's big promise as a sustainable biofuel is in its beans. 40 percent of every jatropha bean has the oil needed to make a biofuel. 20 pounds of those beans can produce one gallon of diesel. It takes 22 pounds of corn to produce one gallon of ethanol; and the process to make ethanol from corn is more involved and energy wasteful than to make diesel from jatropha beans. More importantly, you can produce 4 times as much fuel per acre in a single growing season as you can with corn. Another key factor is the fact that the plants are drought tolerant and don't need high quality soils in order to grow. Obviously, GM (genetic modification) should be able to increase these plants yields well beyond today's currently unbelievable yields.
Jatropha is well on its way as a core biofuel in countries like India and the Philippines. In America, at least when it comes to politics, corn (and the "votes" from corn-based economies in our States) is king. So, little is being said about Jatropha. Much of the experimentation that is going on is being done by farmers in Florida; without Federal support. It is too bad that politics (and voting blocks) have to always get in the way of what's good for our country.
Of course, another dirty little secret in this country is that "all" biofuels are just another dirty form of hydrocarbon fuels. They will pump out as much carbon dioxide and feed into Global Warming as any other carbon-based fuel. The "greens" in this country don't really want more CO2 emitting fuels. So, don't expect the Democrats to go hog wild over any jatropha funding. To the greens, energy independence doesn't mean independence from foreign fuels. Instead it means a society free of energy. They just as soon block a wind farm as they would block any refinery for oil, or ethanol, or jatropha. Deep down inside, they would prefer we all be naked; living in huts; and, foraging for food stocks from plants (And, for sure, not animals!). You know... being "one" with nature! After all, Mother Nature didn't make SUVs!