Assessment of the effect pre-treated using ultrasonic and hydrothermal technique for wheat and corn stalks on biogas generation and methane yield

Current study aims to estimate the impact of physical pretreatment of wheat stalks and corn stalks on biogas production, where two types of pretreatment were used (ultrasonic pretreatment and hydrothermal pretreatment) and three types of animal manure were used as a source of bacteria (cow, sheep and ostrich manure). The results showed a high increment in the amount of biogas generated after pretreatment, as the increase when using ultrasonic pretreatment for wheat stalks inoculated with cow, sheep, and ostrich manure were 31.92%, 20.63%, 155.24%, respectively as compared with untreated samples of wheat stalks. As for the corn stalks, the increase in the biogas when ultrasonic pretreatment for corn stalks inoculated with cow, sheep, and ostrich manure was 57.12%, 43.38%, and 173.05%, respectively, as compared with untreated samples of corn stalks. In hydrothermal pretreatment, the increase in biogas generated by pretreatment for wheat stalks inoculated with cow and sheep manure was 30.57% and 6.10 %, respectively, compared with an untreated sample of wheat stalks. In the hydrothermal pretreatment for corn stalks, the increase was 29.69% and 3.67 %, respectively as compared with untreated sample of corn stalks with the same manure above. An increase was also observed in the amount of methane generated after each of the pre-treated, as the increase in the ultrasonic pretreatment for wheat stalks inoculated cow, sheep, and ostrich manure were 25.25%, 21.96% and 160.78 %, respectively. Whereas, when ultrasonic pretreatment for corn stalks the increase was 88.06%, 54.13%, and 210.91 %, respectively. In hydrothermal pretreatment, the increase in the amount of methane for wheat stalks inoculated with cow and sheep manure was 13.59% and 13.67 %, while, in the corn stalks inoculated with cow and sheep manure was 42.90% and 27.23 %, respectively. Finally, the highest biogas and methane production was obtained when ostrich dung was used as inoculum with wheat and corn stalks pre-treated using ultrasound compared to cow and sheep manure. A substantial accord was seen between the values that were measured and the values that were expected by the modified Gompertz model, as indicated by correlation coefficients that were ≥ 0.96.