Investigation of the possibility of converting wheat and rice straw wastes to fermentable sugar by combining ultrasound pretreatment and cold plasma detoxification

In this study was investigated the possibility of converting agricultural lignocellulosic waste to sugar during the ultrasound-acid pretreatment, acid-thermal hydrolysis and cold plasma detoxification. For this purpose, after collecting wheat and rice straw, ultrasound-acid pretreatment (with three different treatments of bagasse load, sonicate time and acid concentration) and then acid hydrolysis (with three different treatments of hydrolysis time, acid concentration and temperature) on biomass were performed. The results of chemical data showed high sugar were released at 30 min time of sonication, bagasse load of 1% and acid concentration of 1.5% and soluble lignin was at its highest level. Also, during acid-thermal hydrolysis, hydrolysis time of 45 min, acid concentration of 1.5% and temperature of 120 ˚C caused further release of sugar and ASL. In addition to the chemical data, the results of FTIR, FESEM and thermal analysis proved that the structures are well disintegrated and the biomass is prepared for the conversion of sugar to bioethanol. Then, cold plasma detoxification method was used to remove such as acetic acid, formic acid and furfural and the results showed that after cold plasma detoxification, acid inhibitory compounds levels were 73, 58 and 78% decreased during 10 min of detoxification, jet distance of 0.5 cm and argon gas to air ratio 0.5. Finally, it can be said that lignocellulosic compounds can be broken down by ultrasonic pretreatment and acid-thermal hydrolysis of structural polysaccharides, and then the toxic inhibitory compounds can be eliminated by cold plasma method to achieve the best results.