Extraction of juice from sweet pearl millet and sweet sorghum using two experimental press prototypes

Abstract

<abstract> <bold>Abstract.</bold> Juice extracted from biomass of sweet pearl millet and sweet sorghum can be used for bioethanol production. Stalks of both crops are a good source of fermentable sugars. Even though sweet sorghum is known for its bioethanol potential, studies on sweet pearl millet remain scarce. In summer 2012, two experimental press prototypes, a four-roller press and a horizontal hydraulic press, were designed and built at the Department of Soils and Agri-Food Engineering of Université Laval, Quebec, Canada. Both presses were compared in terms of effectiveness of juice extraction to select the most suitable one for an in-field juice extraction system for both crops. Trials using both presses to extract the juice from stalks of both crop species, with or without leaves, were carried out. For both crop species, obtained results showed a higher juice extraction with the hydraulic press than with the roller press. The hydraulic press allowed extracting twice as much juice than the roller press. For both presses, more juice was extracted when leaves were removed from the stalks prior to pressing. The hydraulic press, in particular, allowed extracting 0.366 L kg^-1 of juice from the sweet sorghum biomass without leaves. Sugar content was however the same for both crop species, with or without leaves, whatever the press used. Based on these results, the hydraulic press seems to have a better potential in extracting the juice from both sweet pearl millet and sweet sorghum.