Title: Ethanol from orange processing waste Authors
|Grohmann, Karel - RETIRED USDA|
Submitted to: National Meeting of Institute of Food Technologists/Food Expo
Publication Type: Abstract Only
Publication Acceptance Date: January 15, 2007
Publication Date: April 25, 2007
Citation: Widmer, W.W., Grohmann, K. 2007. Ethanol from orange processing waste. National Meeting of Institute of Food Technologists/Food Expo. Presentation No. 140-09. Technical Abstract: Greater than 90 percent of the oranges produced in Florida are processed for juice production and produce approximately 3.5 billion pounds of waste annually consisting of peel, segment membranes and seeds. The bulk of this waste material is dried and sold as a cattlefeed by-product, often at a production cost greater than the cattlefeed value. Orange processing waste contains approximately 0.8% limonene by weight, and during drying, significant amounts of this volatile material are vented to the atmosphere causing environmental concerns. An alternative to drying this waste for use as a low value cattlefeed is treatment by enzyme hydrolysis and fermentation to produce ethanol for use as an alternative fuel and other by-products. A process has been developed at the pilot scale to reliably produce 4-5% ethanol by volume in liquefied orange waste materials using a combination of enzymatic hydrolysis and fermentation of the sugars by Saccharomyces cerevisiae. The waste is pretreated to remove 90% of the limonene, eliminating microbial inhibition during the fermentation process. The removed limonene is recovered lowering environmental concerns and yields a valuable co-product. The value of limonene varies from $0.50 - $1.00/lb. Currently $0.70 -$0.90 worth of commercially available enzymes consisting of pectinase, cellulase and beta-glucosidase are required to produce a gallon of ethanol with approximately ½ pound of limonene also recovered for each gallon of ethanol produced. The low amounts of enzymes used to reduce costs result in a more viscous fermentation slurry compared to what is obtained after corn fermentation. Further research is being conducted to lower the viscosity after fermentation, improve distillation to produce a fuel grade ethanol more economically from the fermented orange material, and produce other valuable co-products from the residue after distillation.