Collection and transportation costs are often critical. Waste streams Agricultural crops Sugarcane, sugarbeet, corn, and sweet sorghum are agricultural crops presently grown commercially for both carbohydrate production and animal feeds. They use special biochemical pathways to recycle and trap carbon dioxide tht is lost through photorespiration. Sugarbeets are efficient because they store their carbohydrate in the ground. Sugarcane was the basis for the World's first renewable biofuel program in Brazil.
Corn is the basis for the present renewable ethanol fuel industry in the United States.
The sugars produced by these crops are easily fermented by Saccharomyces cerevisiae. The sucrose produced by sugarcane, sugarbeet, and sweet sorghum can be fermented directly after squeesing them from the crop. The residues left over after removing fermentable sugars can also be utilized. In some cases they end up as animal feeds, but many agricultural residues can be converted into additional fermentable sugars through saccharification with cellulases and hemicellulases . The hemicellulosic sugars are not fermentable by S. cerevisiae , and must be converted to ethanol by pentose fermenting yeasts or genetically engineered organisms .