Energy Efficient Microwave Irradiation of Sago Bark Waste (SBW) for Bioethanol Production

The energy efficiency of microwave irradiation for bioethanol production from sago bark waste (SBW) was studied. The maximum sugar yield of 62.6 % was reached at the biomass loading 20% (w/w). The high ethanol yield of 60.2% theoretical yield, ethanol concentration 30.67 g/l was achieved by diluted sulfuric acid supported microwave irradiation with 40% (w/w) biomass loading at 60 h fermentation. The energy consumption of microwave irradiation to produce 1 g sugar and 1 g ethanol was calculated separately. The lowest energy consumption was noticed while biomass loading and energy input were fixed at 40 % (w/w) and 33 kJ (1100 W for 30 s) respectively, and it is amounted to 1.27 and 1.76 kJ to produce 1 g of sugar after enzymatic hydrolysis and 1 g ethanol after fermentation, individually. Usually, 1 g ethanol can produce approximately 27 kJ of energy, and therefore, the energy input for the microwave pretreatment was only 7% of the energy output. The microwave irradiation technique established for SBW to produce ethanol succeeded in 80% energy savings for producing 1 g ethanol compared to rape straw by microwave pretreatment previously reported