| China is a large agricultural country with various types of crop straw resources. There are about 800 million tons of agricultural stalks produced annually in China. As one of the three main crop straws, corn stalk can be converted into biogas through anaerobic digestion technology. Crop stalk has complex structure and high percentage of lignocelluloses, so it is difficult for the anaerobic microbes to degrade lignocelluloses effectively, leading low digestion rate and biogas yield. Therefore, the pretreatment method becomes a key factor in the process of energy utilization of crop straw. At present, chemical pretreatment method is commonly used in lignocelluloses pretreatment, which can destroy the bond between lignin and cellulose effectively and improve the degradation rate of lignocelluloses.Based on our research group's experiments, new pretreatment methods that can improve the anaerobic digestion and gas production by pretreating corn stalk with the mixture of NaOH and chemicals are proposed in this paper, we did pretreatment the corn stalks with the mixture of 2% NaOH and AQ,2% NaOH and GO at room temperature and GO, NaOH and combined pretreatment were did at high temperature.Then research the changes in the main components of corn stalks and gas production of anaerobic digestion.The study was carried out treating the corn stalk with the mixture NaOH, anthraquinone derivatives (AQ) and mixture NaOH, green oxygen (GO) at room temperature,followed the anaerobic gas production experiment with load of 65g·L-1 at 35℃.Compared to 2% NaOH wet pretreatment, the results illustrated that combined pretreatment could improve the dry matter loss-rate of corn stalks and hemicelluloses degradation rate, so that the gas production peak appeared earlier, the total biogas production increased, meanwhile, the anaerobic digestion time shorten. The total biogas production after pretreatment with the mixture of 2% NaOH and 0.1% AQ was 44290mL, about 19% higher compared to the production after 2% NaOH wet pretreatment; the unit VS gas production was 423.8mL·g-1,18.5% higher than that after 2% NaOH wet pretreatment. The better pretreated sample was the combination of 2% NaOH and 0.05% GO, which brought out a total biogas production of 40750ml,1.1 times more than that by 2% NaOH wet pretreatment. Its unit VS gas production was 390mL·g-1,9.1% higher than that of 2% NaOH wet pretreatment samples. Digestion unit VS gas production was 783.1mL·g-1, increased 4.8%, while anaerobic digestion time T80 reduced 5 days.At 35℃,referring to alkaline pulping process, anaerobic digestion experiment was made under the load of 65g·L-1 by pretreating corn stalk with NaOH, GO, NaOH and GO combination at high temperature. The result showed that, the total gas production of 0.5%GO high temperature pretreated sample reached 20240mL, increased about 63% compared with the untreated sample; The gas production of 2%NaOH high temperature pretreated sample was 16280mL, increased 31.1% than the untreated sample. The total biogas production of 2% NaOH and 0.5%GO combination high temperature pretreatment was 19930mL, increased 60.5% compared with untreated sample; However, except 0.5%GO,2% NaOH and 0.5% GO high temperature pretreated samples, no samples can compare with 2% NaOH wet pretreatment sample at total gas production.These results show that combined pretreatment can effectively improve the anaerobic digestion and gas production of corn stalks, increase degradation rate of the components, which provides a new pretreated method for the anaerobic digestion of corn stalks.
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