In 2006, more than 5 billion gallons of fuel ethanol (90% from corn) and 250 million gallons of biodiesel (mostly from soybean oil) were produced in the U.S.
Dry-grind is the most prevalent process for ethanol production and much of the current expansion of the industry uses this technology. However, fuel ethanol is also produced using wet milling processes. The principal differences between the processes are the grain preparation steps and the numbers and types of co-products recovered.
Analysts generally agree that the ability to significantly increase ethanol production using corn grain is limited and that large increases will require the use of lignocellulose resources such as agricultural residues, grasses, and wood. A number of approaches are being explored to overcome remaining technical constraints.
Ethanol production from sucrose (table sugar), while not practiced in the U.S., predominates in tropical regions with sugarcane production such as Brazil.
Biodiesel is made by reacting vegetable oils or fats with alcohol in the presence of a catalyst. Glycerol is produced as a by-product. Soybean oil is the primary resource used, but other virgin vegetable oils (e.g., Canola, castor, peanut, palm, rapeseed, sunflower) and greases and recycled oils (e.g., tallow, yellow grease, trap grease) can also be used.