What problems are there with biofuel?

Answer 1

The main problem with biofuel is trying to make it economically viable. Most of the current methods are simply too expensive, but that will probably change with more research and as petroleum fuel prices continue to rise.

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The above answer is incorrect, the main problem is how to get enough arable land to farm biofuel crops at the first place to provide enough energy for everyone. While the Earth's population is rising at a rapid rate, we are using up food for energy, need more land to build houses and infrastructure. Remember not every land is arable, many of the old arable land like in Africa are unusable because of the salt content. As more soil erosion takes place, less land is arable. Also bio-diversity, monoculture, etc all associated to food chain and the biosphere. This is why there is the seed bank in the North Pole to conserve diversity when a species of plants (crop) extinct.

Greener?

Burning biofuel is much cleaner than gasoline to the environment. Also reduces greenhouse gases.

Why is it not widely use?

Not enough food to produce enough fuel to replace gasoline. Hence it is only mixed with gasoline. Not many cars today manufactured to run on pure ethanol or bio-diesel.

More expensive?

No. Ethanol and bio-diesel are bio-fuel, that you see in gas station are cheaper than regular gasoline.

Burning forest residue and algae to make bio-fuel.

Yes this is being researched and have been tested on airplanes, however not mature yet.