Alkali pretreatment is among the most promising methods for pretreatment. It could modify the structure of lignocellulosic materials by increasing the surface area, reducing the crystallinity of cellulose and hemicellulose and lignin removal, thus significantly increase the degradability of lignocelluloses. However, the efficiency of alkali pretreatment highly depends on the process conditions, i.e. temperature, concentration, and the treatment time, as well as the inherent characteristics of the lignocellulose used.The objective of this research was to develop an alkali pretreatment process prior to anaerobic digestion (AD) of cattle manure and pine wood to improve the methane productivity.Laboratory-scale experiments were carried out in completely batch bioreactors, 118 ml capacity. The mesophilic anaerobic digestions were performed and produced gases were analyzed by gas chromatography.At the first step alkaline treatment with Ca(OH) 2 was used for improvement of biogas production from cattle manure. Effects of temperature (20 °C and 60 °C), time (0, 2, and 12 h), and pH (9, 10, 11, and 12) in liming pretreatment of the manure on biogas production were investigated. The results showed that alkaline treatment at 20 °C was not effective on biogas production. The manure treated at the elevated temperature, 60 °C, produced more methane than the untreated manure. The biogas production was increased with increase in duration time of treatment and pH. The maximum amount of biogas produced was observed from the manure treated for 12 h at pH 12, which was 225.4 ml CH 4 /g VS. This was more than 76% higher yield of biogas than that of untreated manure. The analysis of the treated manure showed that the alkaline treatment eliminated 22.7% of the total lignin, which could be the reason for improvement of digestibility of the manure and increase in biogas production yield.At the second steps, alkaline pretreatment with NaOH was used to improve biogas production from softwood pine. The pretreatments were carried out at different temperatures 0 and 100?C with 8.0% w/w NaOH solution for different periods of time 10,30,60 min. The pretreated materials were then anaerobically digested to biogas.Clear positive effects of the pretreatments on the yield of methane were observed. The best improvement was achieved at 100 o C when 8% NaOH for 10 min was used for the pretreatment, which resulted in 181.2% improvement in the yield of methane production. In addition, treatment with NaOH for 60 min at 0 o C resulted in 118.6% improvement in the methane yield compared to that of the untreated material.The pretreatment resulted in significant reducing the crystallinity of cellulose, and lignin removal, and swelling the structure of wood, which might be responsible for improved biogas production.At the third steps, pretreatment of different parts of pine wood, i.e. stem, trunk, branches, bark, and cones, were studied by 8.0% w/w NaOH under the conditions in which the best improvement was achieved in the second steps(100 o C for 10 min and 0 o C for 60 min). The effects of pretreatment on composition and biogas production of the wood were investigated. Pretreatment of different parts of the tree were studied at the same temperature, NaOH concentration, and solid loading.The results showed that the pretreatment can significantly improve the yield and productivity of the biogas; however, the optimum condition for each part is different and the efficiency of the treatment highly depends on the composition of the different parts. Key words: Alkali pretreatment,biogas,cow manure,pine wood