COMPARATIVE STUDY OF MICROWAVE ASSISTED PRE-TREATMENT METHODS OF RICE HUSK FOR POTENTIAL ENERGY RECOVERY THROUGH ANAEROBIC DIGESTION

Rice husk is a major by-product of the rice-milling industries and it is abundantly available. It has been considered as a waste which causes disposal problems. Until today, open field burning that is often carried out after harvesting season is perhaps the most common practice of handling rice husk in many countries in Asia. Rice husk is commonly disposed via open burning in the field. Such practice leads to the energy being wasted and poses environmental health threats to the public. In the recent years, utilization of agricultural waste and residues for energy recovery has received a lot of attention. Ample availability of rice husk coupled with the continuous development of biomass energy conversion technologies have turned rice husk into a potential source of energy but due to its recalcitrant nature inhibits and slows the digestion of cellulose and hemicellulose, to be converted to fermentable sugars and biofuels. This lignocelluosic biomass is to be treated somehow in order to disrupt the lignin present and to digest the cellulose and hemicellulose in better percentage to get enhanced biofuel production. For this research, there are two objectives to be achieved which are to disrupt the lignin in order to get higher percentage of cellulose and hemicellulose for potential energy recovery and also to determine the best rice husk pre-treatment method for enhanced biofuel production. Four different chemical solutions, two acidic (dilute sulphuric acid and hydrogen peroxide) and two alkaline (dilute sodium hydroxide and sodium carbonate), of 2%, 3.5%, and 5% strength were used for pre-treatments of the biomass. Research conducted shows that the lignin was successfully disrupted after pre-treatment. Based on the results, quantitative analysis (CHNS, UV Visible Spectrophotometer & HPLC) had proven that NaOH with 3.5% concentration is the best chemical for the pre-treatment of rice husk for potential energy recovery. For untreated rice husk, the percentage of cellulose was 38.6% while the pre-treated rice husk with 3.5% concentration of NaOH gives a total of 59.3% of cellulose. From this result, it can be concluded that the best rice husk pre-treatment method for potential energy recovery is by using 3.5% concentration of Sodium Hydroxide (NaOH) where it gives the highest percentage of cellulose.