Corn
Corn is the primary source of the world's fuel ethanol and most of that corn comes from the United States. As of 2012, more than 40 percent of the US corn crop was being used to produce corn ethanol, though not all of ethanol is used as biofuel. Current requirements by the United States government require that roughly 36 billion gallons of renewable biofuel be produced in 2013. Under the renewable fuel standard, up to 15 billion gallons of that will be grain based ethanol, including corn.The Advantages of corn are:
- Infrastructure for planting, harvesting, and processing is already in place.
- Relatively simple conversion of corn starch to ethanol.
- Potential to use the rest of the plant (stalk, cob, etc.) to produce ethanol as well.
- Corn has the potential to supply about ¼ of U.S. gasoline consumption.
- There are no indirect land use costs with corn.
- Relatively high requirement for pesticide and fertilizer. Not only is this expensive, but it leads to soil and water contamination.
- It is a food staple and use in biofuel has increased food prices worldwide, leading to hunger.
- The production rate is low at an average of just 350 gallons of fuel per acre.
- Energy yield is about 1.2, which is just barely positive at 20% net yield.
Sugar Cane
Not far behind corn in terms of overall ethanol production is sugar cane. The majority of the world's sugar cane is grown in Brazil, which was the world's largest producer of alcohol fuel until very recently went it was eclipsed by the United States. Brazil produces roughly 5 billion gallons or 18 billion litres of fuel ethanol annually. The country adopted a very favourable stance on ethanol derived from sugar cane as a result of the oil embargo of the 1970s. Brazil has a policy of at least 22% ethanol in its gasoline, though 100% ethanol is available for purchase.Unlike corn, sugar cane provides sugar rather than starch, which is more easily converted to alcohol. Where as corn requires heating and then fermentation, sugar cane requires only fermentation.
The Advantages of sugar cane include:
- Infrastructure for planting, harvesting, and processing that is already in place.
- No land use changes provide plantations sizes remain stable.
- The yield is higher than that of corn at an average of 650 gallons per acre.
- Carbon dioxide emissions can be 90% lower than for conventional gasoline when land use changes do not occur.
- Despite having a higher yield than corn, it is still relatively low
- Few regions are suitable to cultivation
- Sugar cane is a food staple in countries of South and Central America
Soybeans
Unlike corn and sugar cane, soybeans are grown throughout much of North America, South America, and Asia. In other words, soybeans are a global food crop. The United States produce roughly 32 percent of all soybeans in the world, followed by Brazil at 28 percent. Despite its relatively high price as a food crop, soybean is still a major feedstock for the production of biofuel. In this case, rather than ethanol, soybean is used to produce biodiesel. Soybean is probably the worst feedstock for biofuel production.The Advantages of soybeans include:
- Grows in many regions
- Relatively easy to maintain
- A yield of only about 70 gallons of biodiesel per acre, which is the worst yield of any crop. Palm oil produces almost 10 times as much biodiesel per acre at 600 gallons (note palm oil is considered a second generation feedstock).
- Soybean is a common food source and thus its use as a biofuel directly threatens the food chain.
- It faces a number of disease and pest burdens
- It is generally not a profitable biofuel feedstock.
- More energy is usually required to cultivate soybeans than can be derived from the fuel produced from them.
Vegetable Oil
Vegetable oil, which can be derived from any number of vegetables, can fall into the category of both a first and a second generation biofuel. If used directly as “virgin” vegetable oil, it is a first generation biofuel. If used after it is no longer fit for cooking, then vegetable oil becomes a second generation biofuel. Here we consider only its benefits and drawbacks as a first generation feedstock used in the production of biodiesel.The advantages of vegetable oil:
- It is easy to convert to biodiesel
- It is widely available
- It can often be used directly in diesel engines with little modification
- It is an important feedstock
- When unrefined, it can cause engine damage through carbon deposition due to incomplete combustion
- The replacement of old growth forest with oil palms increases carbon emissions and damages biodiversity.
