Effect Of Alkaline Microwaving Pretreatment On Anaerobic Digestion And Biogas Production Of Swine Manure

Animal manure is one of the major wastes in many agricultural countries due to their intensive animal breeding industry,The increased and concentrated animal waste has become a big challenge that should be treated appropriately.Therefore,the performance and mechanism of swine manure pretreatment by microwave-alkaline were thoroughly investigated in this study in order to find a effective and economy animal manure pretreatment technology.Different factors on pretreatment process,as well as the result of pretreatment on anaerobic digestion and biogas production,were discuss.The effects of microwave pretreatment and hydrothermal pretreatment on swine manure were compared.With SCOD,soluble protein,sugar and VFA as an indicator test,the results show that the effect of microwave pretreatment was better than that of hydrothermal pretreatment in terms of cracking effect,unit energy consumption,reaction rate and treatment products.Single factor experiment is used to inverstigate the effect of microwave power,reaction time and pH of the alkaline microwaving pretreatment on manure.With SCOD,ammonia nitrogen,nitro nitrogen and nitrite nitrogen an indicator test,the results show that long-term and medium-intensity microwave treatment can obtain high SCOD break rate and ammonia nitrogen concentration,which is favorable for subsequent anaerobic digestion and biogas production.Response surface methodology(RSM)was used to investigate the effect of alkaline microwaving process for manure pretreatment at various values of pH and energy input.Results show that the manure disintegration degree was maximized of 63.91%at energy input of 54 J/g and pH of 12.0,and variance analysis indicated that pH value played a more important role in the pretreatment than energy input.Anaerobic digestion results demonstrated that the alkaline microwaving pretreatment not only significantly increased cumulative biogas production,but also shortened the duration for a stable biogas production rate.The mechanism of alkaline microwaving pretreatment on the anaerobic digestion and biogas production was investigated through the changes of pH and nitrogen(ammonia nitrogen,nitro nitrogen and nitrite nitrogen)in the process of anaerobic digestion.The ammonium nitrogen concentration was lower and pH presented weak alkalinity during anaerobic digestion process,which could both promote the growth of methanogens.Therefore,the alkaline microwaving pretreatment could become an alternative process for effective treatment of swine manure.