27 August 2009

New type of biofuel: Hold the seeds

Watermelon juice can be a valuable source of biofuel.

The juice of reject watermelons can efficiently ferment and convert to ethanol, said Wayne Fish, who worked with a team of researchers at the USDA-Agricultural Research Service’s South Central Agricultural Research Laboratory in Lane, Okla.

The team’s goal was to evaluate the biofuel potential of juice from cull watermelons, those not sold due to cosmetic imperfections, and currently ploughed back into the field.

“About 20% of each annual watermelon crop is left in the field because of surface blemishes or because they are misshapen,” Fish said. “We’ve shown that the juice of these melons is a source of readily fermentable sugars, representing a heretofore untapped feedstock for ethanol biofuel production.”

As well as using the juice for ethanol production, either directly or as a diluent for other biofuel crops, Fish said it can be a source of lycopene and L-citrulline, two “nutraeuticals” for which enough demand currently exists to make extraction economically worthwhile. After taking these compounds out of the cull juice, you can still ferment it into ethanol, he said.

“At a production ratio of ~0.4 g ethanol/g sugar, as measured in this study, approximately 220 L/ha of ethanol would be produced from cull watermelons,” Fish said.

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