Factors And Performace Study For Anaerobic Digestion Of Livestock Manure For Biogas Production

With the rapid development of Chinese animal husbandry, increasing pollution dueto livestock manure is seriously affecting the ecological environment. The environment,air, water and/or soil lead are polluted and human health endangered when animalmanure is not properly disposed-off. On the other hand, the Chinese fossil energystructure has been a serious challenge. There is an urgent need to develop new clearenergy system. The anaerobic digestion of livestock manure for making biogas utilizeslivestock manure but also provides clear renewable energy. This subject focuses oninfluencing factors and characteristics of anaerobic digestion process of livestockmanure for making biogas.Influencing factors of the anaerobic digestion, such as temperature, organic load,type of material, have been chosen for this study based on relevant literature researchand real farm conditions. The study has been carried out in batch experiments andsemi-continuous experiments. For the study an Anaerobic Baffled Reactor （ABR） andUp Flow Anaerobic Sludge Bed （UASB） were designed. These anaerobic reactors werethen activated and run. To obtain optimum operating conditions, reactor parametersstudied, such as biogas production rate, biogas yield, VFA and ammonia concentration,by changing operation condition.Summary of the results are as follows:（1） Compared with23℃,35℃is more suitable for anaerobic digestion of animalmanure. At35℃, the microbes grow faster, show higher biological activity, and thusproduce more biogas with higher methane percentage. With35℃temperature, biogasyield was higher (5.8mL_gas/mL_feed) than with23℃temperature (0.9mL_gas/mL_feed) insame organic load,30gCOD/（L·d）.（2） Pig manure is a better substrate of anaerobic digestion than cow manure. Forbiogas yield, anaerobic digestion of pig manure （80mL/d） was higher than that of cowmanure （43mL/d） at35℃, in same organic load,30gCOD/（L·d）.（3） The higher organic load set, the greater biogas production rate （mL/d） we got.In the semi-continuous experiment, biogas production rates were80mL/d,69mL/d,30mL/d respectively when orgainic load were30gCOD/（L·d）,20gCOD/（L·d）,10gCOD/（L·d）.（4） UASB reactor had better and stable production rate than ABR. The biogasproduction rate of UASB reactor was up to32.1gCODCH4/（L·d） with organic load52.2gCOD/（L·d）. The biogas production rate of ABR reactor was4.03gCODCH4/（L·d） withorganic load6.0gCOD/（L·d）, wich was less stable than UASB reactor. （5） Methane percentage in biogas of UASB reactors and ABR reactor wasstabilized at a very high level of75%-80%which is not affected by organic load andthe types of reactors.（6） UASB reactor without recycle is better than UASB reactor without recycle.Change in granule volume affect the numbers of microorganisms in the reactor, whichcan affect the anaerobic digestion react. Granule volume range of the UASB reactorwithout recycle was120mL-140mL stably. But Granule volume range of ABR（70mL-110mL） and UASB reactor with recycle （80mL-130mL） floated bigger.（7） COD removal rate of UASB reactor was not as stable as the ABR reactor. CODremoval rates of UASB reactor was75%in12.2gCOD/（L·d） organic load, which issame as ABR reactor. But COD removal rate of UASB reactor down to40%-50%afterwards, which is much lower than ABR reactor.