Experimental Studies On Anaerobic Digestion Of Straw Stalk Mixed With Pig Dung

Our country is an agricultural country, producing about700million tons crop stalks a year, of which50%have not been rational used and large quantities have been discarded or burned, it caused serious environmental pollution, also a great waste of resources. In recent years, large-scale animal husbandry, particularly the rapid development of aquaculture. makes environment pollution problem caused by manure become increasingly prominent. Meanwhile, with the development of biomass energy and the promotion of resources and technology, biomass waste resources has become an effective way to solve these pollution problems.Under mesothermal condition (35℃),this experiment uses self-made CSTR anaerobic reactor to make mesothermal anaerobic digestion experiments under different organic loading, to study the effects of different organic loading on anaerobic digestion reaction of pH.ammonia nitrogen, VFA, alkalinity, gas production and methane production rate indexes, and to analyze system’s gas production performance and stability through the data from the experiment to find the optimum conditions for anaerobic digestion. Experimental results show that:(1)In the early stage of anaerobic digestion pH values slightly decreased, the pH value decreased from7.13to6.70and then gradually increased to7.31; at last it will be stable at around7.30. The pH value between6.8and7.5is the methane bacteria’s most suitable pH value range. From the whole process of anaerobic digestion, the pH value of the system range always changes in methane bacteria’s most suitable value for pH.(2)In the feeding organic load which is0.5-2.0gVS/(L·d), average daily gas production is869-3232ml, when organic load is between0.5-1.5gVS/(L·d), gas production gradually increased, and when the organic load is1.5gVS/(L·d), gas production reached the maximum of3232ml.(3)In the whole process of anaerobic digestion, the concentration of ammonia and nitrogen has little changes, ammonia-nitrogen concentration is maintained at between522-850mg/L and is not high, which is conducive to the growth of the methanogens. (4)In the process that feeding organic load gradually increased from0.5gVS/(L·d) to2.0gVS/(L·d), the concentration of VFA increased first and then decreased from1520mg/L and at last it remained stable. When the organic load is1.5gVS/(L·d), VFA concentrations were highest for3420mg/L.(5)In the whole process of anaerobic digestion, the concentration of total alkalinity has been stable at2129-2462mg/L.The concentration of total alkalinity is not high. The moderate alkalinity in the process of anaerobic digestion amount is important to the entire anaerobic digestion; it can increase the buffer capacity of the system, so as to improve the stability of system.(6)When feeding organic load in the0.5-1.5gVS/(L·d), methane volume fraction increased with the increasing organic load. In the interval1.5-2.0gVS/(L·d) the volume fraction of methane decreased slightly. And when the organic load is1.5gVS/(L·d), the maximum of methane volume fraction is55.2%. At that time the organic load is1.75gVS/(L·d) the average methane production is1628ml one day.