Effects of lime pretreatment on biogas production from dry dairy cattle manure

Aim. The main goal of the current study was improvement of biogas production from cattle manure with Ca(OH)(2) pretreatment. Methods. Effects of temperature (20 degrees C and 60 degrees C), time (10 min, 2, and 12 h), and pH (9, 10, 11, and 12) on liming of the manure on biogas production was investigated. Cattle manure treated at different alkali conditions was subjected to anaerobic digestion and the methane produced during 45 days was measured. Results. The results showed that alkaline treatment at 20 degrees C did not affect the biogas production, while the manure treated at 60 degrees C produced more methane than the untreated one. The biogas production was increased by increasing the pH and treatment time. Maximum improvement in methane production was achieved by pretreatment at pH 12 for 12 h, and resulted in 225 ml CH4/g VS which was 76% higher than the methane yield obtained from untreated manure. The analysis of the treated and untreated manure showed that the alkali treatment eliminated 22.7% of the total lignin. Lignin removal may be the reason of improvement in digestibility of the manure and consequently the yield of biogas Conclusion. Lime pretreatment is a promising method for improvement of biogas production from cattle manure