People may speak about biofuels, like vegetable based gas, as a great replacement for traditional fossil fuels. Although it would be a great help to our energy crisis, it won't do quite enough. The problem is biofuels still will produce some pollution. Through thoughtful engineering, they may create less pollution, but they will still create some.

However, there is one very useful thing about biofuels. If all we need to make biofuels is vegetables, then it should be pretty easy to get, because we can grow vegetables in fields just about anywhere, whereas for fossil fuels, we have to search around and find it, since it came essentially from dead plant and animal matter (hence the name fossil fuels). It's hard to predict where this will happen, and even then, there's only so much of it buried in the Earth, and we're eventually going to run out, likely very soon.

In theory, vegetable fuel is derived ultimately from sunlight and thus is recyclable, returning gasses into the atmosphere; they were removed to make the oil itself. Fossil fuel on the other hand is not recyclable and therefore limited, and burning it alters the composition of the atmosphere in ways we may not want.In practice, most vegetable oil is grown with fertilizer, which is in turn made from fossil fuels. As a consequence, the reasons why it would be a good idea usually don't apply.

It took millions of years to make fossil fuels, and we're running out of them. In principle, we won't run out of plants: we can grow new crops every year. Some kinds of plants are better than others for reducing fossil fuel usage. For example, producing a gallon of fuel from corn requires about 7/8 of a gallon of fossil fuel because corn requires fertilizing and extensive chemical processing. So corn doesn't save much fossil fuel. A gallon of fuel from sugar cane, on the other hand, requires just 1/8 of a gallon of fossil fuel. Brazil "grows" a lot of its gasoline as sugar cane, while we in the U.S. still have to import most of our oil.

The primary benefit is that corn is easy to grow so we can always produce more of it. Fossil fuels took millions of years to create, so more cannot be created quickly enough to keep up with demand. You didn't ask about the downsides of vegetable-based fuels, but I'd like to tell you that they are very problematic as well. Growing corn takes a lot of land, a lot of water, and a lot of fossil-fuel-derived fertilizers. It doesn't seem to be a good fuel alternative.