Ethanol

Ethanol is an alcohol made by fermenting biomass through a process similar to brewing beer. Ethanol can be made from any feedstock that contains significant amounts of sugar (such as sugar cane) or materials that can be converted into sugar, like starch (such as corn). Ethanol derived from corn is the most widely used biofuel in the United States, and the amount of corn dedicated to ethanol production is growing steadily.

Biodiesel:

Biodiesel is a fuel for diesel engines and, like ethanol, can be made from a variety of raw materials. By far the most common feedstock in the United States is soybeans, though rapeseed, mustard, palm oil, hemp, waste vegetable oils and animal fats can also be used. Even as biodiesel contributes only a small part to the current biofuels mix, large-scale production of soybeans is already plagued by problems stemming from intensive industrial agricultural practices. Production of biodiesel in Southeast Asia, particularly from palm oil in Indonesia and Malaysia, has been linked to increased deforestation as forest lands are cleared for feedstock cultivation.

Cellulosic Ethanol:

Cellulosic ethanol is produced from the sugar contained in cellulose, the woody, structural part of the plant. Currently, the process of producing cellulosic ethanol on a commercial scale remains at the research and development stage due to technological and cost barriers. The two most prominent feedstocks for cellulosic ethanol are agricultural residues, such as corn stalks, and perennial energy crops, such as switchgrass and fast-growing trees. Cellulosic ethanol offers many environmental advantages when compared to corn because the feedstocks are easier to grow -- they are often native species that need less fertilizer and herbicides, and can be more easily integrated with local agricultural systems. However, overproduction and unsustainable management would negate the ecological promise of these feedstocks.