Around 20 per cent of all watermelons grown in the US are ploughed back into the field because they are misshapen or have surface blemishes, according to Wayne Fish of the USDA-Agricultural Research Service's South Central Agricultural Research Laboratory in Lane, Oklahoma.
Fish and his team sought to find a use of these cull fruit. After analysing the juice, they concluded that it could be tapped as a source of lycopene and L-citrulline – and that extraction would be economically worthwhile.
Moreover, after these nutrients have been extracted, the juice – which is rich in readily fermentable sugars – could still be made into ethanol.
They concluded: "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".
Biotechnology for Biofuels (in press)
“Watermelon juice: a promising feedstock supplement, diluent, and nitrogen supplement for ethanol biofuel production”
Authors: W. Fish, B. Bruton, V. Russo