Bioethanol Production from Elephant Grass (<i>Pennisetum purpureum</i>)

Abstract

The problem of global warming has been undeniably accepted worldwide. One of the causes of this situation is the increase in the greenhouse gases. This study was carried out to produce bio-ethanol from elephant grass (Pennisetun purpureum). The grass was sun dried, milled and pretreated by steam explosion method at 160oC. Seven sets of 350 g of the sample was mixed with 350 ml of water boiled at 100^oC and left to stand for 24 hours, after which it was sieved. Sets of 25 ml extract was decanted into reactor bottles and autoclaved at 121^oC, at 15 psi for 15 mins. Five milliliter (5 ml) of Saccharomyces cerevisiae of 0.98 optical density and 5 ml of Aspergillus spp., was then introduced into the reactors. The reactor bottles were corked properly, sealed with aluminum foil and rocked at room temperature for 6 days. Samples were pooled and taken for distillation at 24 hours intervals. Ethanol yield increased from day one to sixth day, which had ethanol yield of 9 ml from 25ml of plant extract while the control had 0.5 ml ethanol yield on day 6. The pH of the medium decreased from 6.50 to 6.00 for the reactor bottle containing microbial inoculants and the control had a pH of 5.53 to 5.85 while the temperature of the reactor bottle containing the microbial inoculants increased from 25^oC to 30^oC and the control had a temperature of 24^oC and 28^oC. The optimized condition for ethanol production was established at pH 6.0 and temperature 30°C. Under these conditions, an ethanol yield of 9 ml was obtained from 25 ml of plant extract. The control experimental setup showed low ethanol yield of 0.5 ml of 25 ml of plant extract.

Keywords: Elephant grass, bioethanol, reactor, Sacharromyces cerevisiae