In this study

ultrasonic field was applied during potassium hydroxide (KOH) pretreatment of wheat straw (WS). Three concentrations of KOH (2%

4%

and 6%) were tested during pretreatment. The results showed that there was a significant influence of the ultrasonic assisted KOH pretreatment (KOH

Upt

) on physiochemical characteristics of WS during pretreatment as well as on digester performance. The pretreatment time was optimized to 36 h for all KOH concentrations. The highest total volatile fatty acid (TVFA) productions (3189 mg·L

-1

) from 6% KOH

Upt

samples were observed. Similarly

the SEM analysis and FTIR observation revealed that KOH

Upt

effectively disrupted the physical morphology of WS and successful breaking of lignin and hemicellulose linkage between carboxyl groups. Moreover

the highest biogasification (555 ml·(g VS

loaded

)

-1

) and biomethane productions (282 ml·(g VS

loaded

)

-1

) from 4%KOH

Upt

digesters

with 69% of biodegradability

indicated significant availability of organic matter from KOH

Upt

. The

R

2

values (0.993-0.998) in Modified Gompertz Model indicated that the model was feasible to predict methane yield for this study. Similarly

the Bo values for 4%KOH

Upt

(283.30 ± 2.74 ml·(gVS

loaded

)

-1

) were also in agreement to the experimental methane yield. These results suggested that ultrasonic addition during KOH pretreatment of WS can effectively increase the organic yield during pretreatment. Moreover

the increase in methane production from 4% KOH

Upt

suggested that digester performance can be improved with lower KOH concentrations using this pretreatment.