Vol. 23 - No. 4 MINERVA BIOTECNOLOGICA 77 1 Department of Chemical Engineering Isfahan University of Technology, Isfahan, Iran 2 Department of Chemical and Biological Engineering Chalmers University of Technology, Gothenburg, Sweden ORIGINAL ARTICLES MINERVA BIOTEC 2011;23:77-82 H. S. NIASAR 1 , K. KARIMI 1 , H. ZILOUEI 1 , P. SALEHIAN 1 , A. JEIHANIPOUR 2 Effects of lime pretreatment on biogas production from dry dairy cattle manure Aim. The main goal of the current study was impro- vement of biogas production from cattle manure with Ca(OH) 2 pretreatment. Methods. Effects of temperature (20 °C and 60 °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 dige- stion and the methane produced during 45 days was measured. Results. The results showed that alkaline treatment at 20 °C did not affect the biogas production, while the manure treated at 60 °C produced more methane than the untreated one. The biogas production was incre- ased by increasing the pH and treatment time. Maxi- mum improvement in methane production was achie- ved by pretreatment at pH 12 for 12 h, and resulted in 225 ml CH 4 /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 improve- ment 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 ma- nure. KEY WORDS: Biofules - Manure - Pretreatment. Acknowledgments.—The authors would like to acknowledge Dr. Mo- hammad Khorvash at the Department of Agriculture, Isfahan University of Technology (Isfahan, Iran) and Ilona Sarvari Horvath at the School of Engineering, University of Borås (Borås, Sweden) for their scientiic supports. Received on September 16, 2011. Accepted for publication on November 16, 2011. Corresponding author: K. Karimi, Industrial Biotechnology, Depart- ment of Chemical Engineering, Isfahan University of Technology, Isfa- han, 84156-83111, Iran. E-mail: karimi@cc.iut.ac.ir M anure is a cheap and widely available feedstock for biogas production. 1-3 However, the overall eficiency of anaerobic digestion of manure is lim- ited due to the presence of recalcitrant materials in the residual organic matter. 2 Animal diets varied in their concentrate level and in forage composition. 4 Lignocelluloses are of- ten the major or sometimes the sole components of manure. The irst step of digestion process for biogas production is hydrolysis of these materials. These lignocelluloses have recalcitrant structure, and a pretreatment process is necessary to improve their biological digestibility. 5, 6 Physical, chemical, and biological pretreatment methods as well as their combinations are suggested for pretreatment of lignocellulosic materials in order to enhance their digestibility and conversion to biogas. 5, 7-10 Alkali pretreatment is among the most effective methods used for this purpose. 11-17 Factors inluencing the performance of alkali pre- treatment are particle size, liquid to solid ratio, pH, temperature, reaction time, and the type of chemi- cal used. Furthermore, the length of the macromol- ecules, degree of polymerization of cellulose, con- iguration of the cellulose chains, and association of MINERVA MEDICA COPYRIGHT®