Microwave Assisted Acid Hydrolysis of Brown Seaweed Ascophyllum nodosum for Bioethanol Production and Characterization of Alga Residue

For the first time, brown seaweed Ascophyllum nodosum was studied as a feedstock for the production of bioethanol. Saccharification was carried out by microwave assisted acid hydrolysis. The optimal condition was 0.4 M H2SO4, 3.13% (w/v) of biomass concentration, reaction temperature at 150 degrees C for I min, resulting in 127 mg/g monosaccharides of seaweed being released. The hydrolysates solution was concentrated and fermented directly without further detoxification. The concentration of furfural, hydroxymethyfufural and phenolic in the fermentation medium were 0.00, 0.01 and 1.8 g/L, respectively. An ethanol concentration of 5.57 g/L and a conversion efficiency of 60.7% (based on glucose, galactose and mannose) were achieved. More than 50% energy yield of alga residue was recovered after hydrolysis, and the energy densification ranged from 1.4 to 1.7, with HI-IVs from about 19-24 MJ/kg. The findings of this study demonstrated that microwave heating is a fast and efficient way to produce sugars and biochar in one simple process. And Ascophyllum nodosum can be potentially used as a feedstock for bioethanol and biochar production.