Effect of agitation on anaerobic digestion of household and similar waste under mesophilic regime

Currently,following the example of solar photovoltaic and wind power,the anaerobic digestion can be a strategic choice for the promotion of green energy in morocco,thanks to the significant potential of biomassavailable in the kingdom and due to its strong commitment to environmental protection and promotion of sustainable development. although the sector appeared to be very promising,it remains largely unexploited,can be explained by its relatively low yields due to the non-masteryof the process. this study is put forward in that context which focuses on the optimization of this process operating conditions,specifically the study of the influence of the agitation on its effectiveness. therefore,we performed a series of experiments covering the variation of the mode,intensity and agitation frequency. as for the mode,we choose three types of agitation (continuous,intermittent and without agitation),in terms of intensity,we took values ranging between 20,40,60,100 and 160rpm (revolutions per minute),and as to the frequency,we opted for a range of 2h,4h,8h and 12h. for all experiments,the fermentation has been carried out under a temperature of 40°c ± 0,6 which constitutes a mesophilic system,with a retention time fixed at 21 days and a reduction in particle size to 10 mm [1-3]. the results showed a significant reduction of approximately 62% of the production of biogas for digestion without agitation,compared to the two other systems with continuous or intermittent agitation,which is mainly due to the formation of a crust at the surface preventing the proper degassing. other experiments with different agitation intensities demonstrated that an agitation at low rotation speed,under the intermittent mode,allows a better biogas production. as for the frequencies of agitation,they were validated in such a way as to avoid crust formation in the digester in order to ensure better efficiency of the process.