Improving Anaerobic Conversion of Pulp Mill Secondary Sludge to Biogas by Pretreatment, 2009 TAPPI Engineering, Pulping, Environmental Conference

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A laboratory study was performed to examine the effectiveness of thermal, caustic, and sonication pretreatment methods in improving anaerobic conversion of secondary sludge samples obtained from a kraft mill and a sulfite mill to biogas. The results show that all three methods improved the anaerobic digestion rate and the biogas yield of the sludge samples, with thermal pretreatment the most effective, followed closely by caustic pretreatment, and sonication the least. The results also show that the biogas production from the untreated sulphite mill sludge was four times higher than that from the untreated kraft mill sludge, and that the soluble carbohydrate content in the sludge correlates well with the biogas yield; it thus may be used as a predictor of the biogas production potential of the secondary sludge.