Sunday, May 3, 2009
3-33
The effect of wet oxidation pretreatment method on rape straw fibres for bioethanol production
Efthalia Arvaniti Jr. and Anne Belinda Thomsen. Biosystems, Risoe National Laboratory for Sustainable Energy DTU, BIO-301 Frederiksborgvej 399, Roskilde, DK-4000, Denmark
Rape plant is extensively used in biodiesel and food oil production industry. The leftovers of the plant, the straw is typically burned or spread back to the land. Rape straw is rich in sugars, and if properly pretreated with chemicals and enzymes, can be well fermented into ethanol by yeasts. In this study, rape straw fibres are pretreated by oxidants, such as oxygen gas and hydrogen peroxide at increased temperature. Focus is given in the oxygen pressure, the concentration of hydrogen peroxide, the effect of washing of the fibres after the treatment, the effect of recycling of the water phase, and pre-soaking of fibres.
The output of the wet oxidation pretreatment is a fibrous cake enriched in cellulose, and a water phase consisting of oligomeric derivatives of hemicellulose. Lignin, the third main component of biomass, is partly left in the fibres and partly oxidised or hydrolysed to phenolic compounds in the water phase. The fibrous cake can be used for ethanol production through simultaneous saccharification and fermentation (SSF), using cellulolytic enzymes and a C6-fermenting organisms e.g. S. cerevisiae. The pretreatment should be effective enough to induce break down of the coherence of the cellulose fibrils through removal of lignin. On the other hand, the pretreatment should be mild enough to avoid formation of degradation products of sugar and lignin, which are inhibitory for SSF. Enzyme digestibility of cellulose enriched filter cakes, and degree of inhibition under SSF, are used as tools for assessing the pretreatment strategies.