Agricultural Research Service (ARS) studies in Lane, Okla., have shown that simple sugars in watermelon juice can be made into ethanol. In 2007, growers harvested four billion pounds of watermelon for fresh and cut-fruit markets. Around 800 million pounds–or 20 percent of the total were left in fields because of external blemishes or deformities.
Normally, this biofuel is produced from cane crops like corn, sorghum or sugarcane as a cleaner-burning alternative to gasoline. The watermelon work reflects a national push by ARS to diversify America’s “portfolio” of biofuel crops that can diminish the reliance on petroleum, especially from foreign suppliers.
With their sweet, refreshing juices and succulent interior, watermelons are a favorite summertime treat, especially around July 4th.
Chemist Wayne Fish’s ethanol studies at the ARS South Central Agricultural Research Laboratory in Lane complement ongoing research there to commercially extract lycopene and citrulline from the crop. Both are valued nutraceutical compounds thought to promote cardiovascular and other health benefits.
In publication-pending studies, Fish showed ethanol can be fermented from the glucose, fructose and sucrose in waste-stream juices what’s left after lycopene and citrulline are extracted. Making ethanol offers the potential benefits of helping to defray sewage treatment costs associated with nutraceutical extraction, and providing watermelon growers with a new market for their crop. Lane scientists also are examining annual ryegrass, sorghum and other crops that could be rotated with watermelons to furnish processing plants with a year-round supply of nutraceuticals or ethanol.
On average, a 20-pound watermelon will yield about 1.4 pounds of sugar from the flesh and rind, from which about seven-tenths of a pound of ethanol can be derived. To extract all the possible sugars, Fish is seeking to degrade the rind with chemical and enzyme treatments. He’s also evaluating different combination of temperatures, yeasts, antifoaming agents and pH levels to optimize the system.
Watermelon is an important crop in many parts of the world. Watermelon production in the U. S. has increased from 1.2 M tons in 1980 to 2.2 M tons in 2004 with an at-farm value of $310 million. Over four billion pounds of watermelon were produced in the United States in 2007 for the fresh produce and cut fruit markets
Root-knot nematodes are microscopic worms that occur in many field and garden soils. Nematodes invade the roots of watermelon and most other vegetable crops, causing extensive damage to the roots. Consequently, growth of the watermelon plant is stunted, and watermelon fruit quality and yield are reduced. Wild species of watermelon that grow in Africa and Asia have wide genetic diversity and are known to possess resistance to a broad range of pests and diseases. ARS scientists evaluated plants of the different wild watermelon species and identified a few wild types that are resistant to nematodes. Plant breeders will cross pollinate these resistant plants with susceptible cultivated watermelon in order to develop resistant cultivated watermelon. Planting resistant watermelon varieties would reduce the need for pesticides to control nematodes in watermelon.
Water-melon is a rich source of at least two compounds that support cardiovascular health, and may serve to prevent a number of diseases. One of these is lycopene, which provides the red color to watermelon, and is a powerful antioxidant carotenoid shown to be important in prostate health.
The second compound, citrulline, is a naturally occurring amino acid involved in maintaining the body’s nitrogen balance and indirectly, in cardiovascular health. During extraction of these neutraceuticals a waste stream is developed which produces readily fermentable sugars that can be used in production of bioethanol. Scientists at the Wes Watkins Agricultural Research Laboratory (WWARL) are investigating the fermentation properties and applications for bioethanol derived from watermelon.
A watermelon is nominally 60% flesh, and about 90% of the flesh is juice that containing 7-10% sugars; over 50% of a watermelon is readily fermentable liquid. An immediate application is the integration of a watermelon juice processing waste stream to be used in bioethanol production. Since it is mostly water, watermelon juice could serve to dilute concentrated sources of fermentable sugars such as molasses. The ready-to-ferment glucose, fructose, and sucrose, would serve as a supplement to the process and reduce primary feedstock requirements by up to 10%. The rind, about 40% of the watermelon fresh weight is equally rich in citrulline. Once juice has been extracted from the rind and flesh, about 10% of the original weight of the whole watermelon is left as a mixture of complex carbohydrates that potentially can be broken down into fermentable sugars.
Bioethanol is considered as a fuel and its production has become a great issue in the world. In concern of energy related environmental pollution, ethanol has been proposed as a clean and efficient energy carrier.it is already used as a cleaner-burning alternative to gasoline and it is the only fuel whose oxidation products do not contain much carbon dioxide and do not contribute to ozone depletion or acid rain
From other experiments on corn and molasses it was found out that both require lots of water and sometimes nitrogen supplements to prepare them for fermentation. The team suggested that watermelon juice from reject watermelons could drastically cut down on water usage, supply needed nitrogen and even add some sugar to the mix, cutting the amount of corn or molasses by up to 15%
The main essence of this research is to provide a method for producing bioethanol without ethical problems such as waste of food resources, as compared to utilization of existing crop biomass or wood-based biomass.
The methods used in this research include; Mash preparation, Fermentation, and Distillation and with percentage yields of ethanol showing that ethanol can be obtained from watermelon.