The process of anaerobic digestion is highly influenced by the environmental and operational factors like organic acids concentration and the reactor volume occupied by the feed material. The optimum level of organic acids is commonly assumed to be in the range between 2,500 and 3,500 mg/l for the anaerobic digestion process. It was observed that the production of total organic acids during hydrolysis of grass using cattle dung slurry (CDS) as the inoculum reached up to 4,850 mg/l in 6 days, while on the other hand it reached 5,700 mg/l within 4 days when rumen content was used as inoculum. The organic acids production continued to the 30th day in the case of rumen content, while in the case of CDS it stopped within 10 days because of pH drop. As compared to CDS the anaerobic digestion of grass with rumen content showed better degradation and biogas production with nearly 80% of methane and up to 80 and 95% reduction in chemical oxygen demand and organic acids respectively.

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