Pretreatment of cocoa waste for bioethanol production using ionic liquid

Abstract

One of the major advantages of biofuel over fossil fuel is that it is environmentally friendly but unfortunately most of the chemicals used in the pretreatment of lignocelluloses biomass to produce biofuel can cause adverse effects to the environment. In this study, ionic liquid was used for the pretreatment of cocoa waste. Its effectiveness in the treatment process was compared to the alkalis and acids used in the conventional pretreatment media. The effectiveness of pretreatment using ionic liquid, H2SO4 and NaOH was based on the reduction of biomass, production of reducing sugar and also bioethanol. Ionic liquid pretreatment was found to show minimal biomass loss of only 31% after pretreatment compared to H2SO4 and NaOH which showed loss of 61% and 79% respectively. The untreated biomass has 10% amount of cellulose but upon pretreatment with ionic liquid, H2SO4 and NaOH, significant amount of cellulose was detected compared to NaOH which produced only 7% of cellulose. Two types of yeasts were also isolated from Malaysian local fermented food, the tapai ubi which were tested for the abilities to ferment the reducing sugar produced. Using the DNS method for determining reducing sugar, ionic liquid pretreatment was shown to produce 6.3×10-2g/L of reducing sugar while the untreated, H2SO4 and NaOH pretreatment produced 2.87×10-2g/L, 7.4×10-2g/L and 3.37×10-2g/L respectively at the end of 24 hours of incubation. Bioethanol produced during the fermentation was analysed using gas chromatography. Ionic liquid produced a total of 7.885g/L, H2SO4 produced 7.911g/L NaOH produced 6.824g/L and untreated cocoa waste produced 5.116g/L of ethanol at the end of 24 hours incubation.