A lump of coal comes is derived from what is believed to be the remaining parts of prehistoric vegetation and other biological matter subjected to processing in the Earth over time. Because of that processing, we do not refer to that lump of coal as a "biofuel." It is, rather, a "fossil fuel." For the sake of comparison, if you were to travel back to when the wood, leaves, and seed-shells had just fallen, and process that matter directly into a fuel, that fuel would then be regarded as a biofuel.
A biofuel is produced from recently-living organic material, or "biomass." Biomass can be converted directly into energy, sticks, leaves and all - the firewood burning in your fireplace on a winter night is one form of biofuel. More typically, the biomass is converted into liquid, gas, or solid fuels.
Sorghum is a grass used primarily as animal feedstock in the United States and much of the rest of the Americas. In other parts of the world, however, sorghum is used more expansively, and it is even used to make alcoholic beverages in West Africa and China.
Sorghum's most familiar use for human consumption in the United States remains sorghum syrup, which can still be found in much of the South. However, sorghum-based foods are now becoming more popular in the health food market since sorghum is gluten-free and makes a good substitute for wheat and other grains.
Sorghum's value to the world is relevant to its value as a bioethanol feedstock. Among agriculturally harvested grasses, sorghum has qualities that make it highly drought-resistant. The sorghum plant enters into a dormancy phase when other plants simply die from lack of water. After enough days without rain, the plant's leaves naturally curl in a way to conserve water most efficiently.
Sorghum requires less plowing to plant effectively than other crops. It has a higher degree of speciation than other grains, too, making it famously disease and pest-resistant.
As a feedstock for biofuels, sorghum's primary use is to produce bioethanol. Bioethanol is alcohol produced by fermenting sorghum and other starch crops. While bioethanol is the most highly manufactured biofuel in the United States, sorghum is probably the least familiar bioethanol feedstock, well behind corn and sugarcane. One bushel of sorghum yields 2.7 barrels of ethanol.
Bioethanol made from sorghum, sugarcane, corn and other edible feedstocks grown on arable land are known as "first generation." "Second generation" bioethanols are made from lignocellulosic biomass, or biomass that isn't from food sources, such as bark, wood chips, and sawdust. Beyond this, there is the largely experimental "third generation," using algae as feedstock, and an even more speculative "fourth generation" that seeks to work with photobiological solar fuels.
Sorghum's characteristic hardiness, its need for just one-seventh the amount of water needed by sugarcane, gives it an important role in the distinction between first and second generations. It would be appropriate to consider it the "most second generation" of the first generation feedstocks since it needs the least arable of arable lands, and is far less consumed as food than corn and sugarcane.
Looking Ahead With Sorghum
A first generation biofuel like those made from sugarcane and corn, sweet sorghum is converted in the same manner. The plant grows to twenty feet and stalks are especially sugary, making them more productive of alcohol. They are pressed into a juice which is then allowed to ferment. Finally, the alcoholic juice is distilled into ethanol.
Grain sorghum is starchier than sweet sorghum and grows to between three and six feet. While it grows in climates worldwide, the United States is grain sorghum's leading producer. It has recently been recommended to be upgraded to the status of ‘advanced biofuel’ by the Environmental Protection Agency. The Department of Energy has also granted an extra $16 million for research into further varieties and uses.
We may be about to have a return toward levels of sorghum consumption not seen since the early 19th Century, when annual harvests were 20 times what they would be a century later. That consumption was primarily on top of pancakes, while today we're fueling cars with grain sorghum derived biofuels. Today, there seems to be almost as much energy behind this hardy, starchy grass as there is packed within it.