Study On Energy Production By Anaerobic Digestion Of Fruit And Vegetable Wastes

The fruit and vegetable wastes(FVW),with high content of water,organic matters and nutrient content,are suitable to anaerobic digestion processing extremely;simultaneously the biological energy methane can be produced.The anaerobic digestion of FVW has great development potential and application prospect for combining solid waster's decrement and energy regeneration together. Using two-phase anaerobic digestion to treat fruit and vegetable wastes under mesophilic conditions(35℃),the fermentation type,use order of digestion product in methane production phase,the removal efficiency of COD,The biogas yield and solid decrement effect of FVW were studied by three stages experiment in a self-designed pilot-scale reactor.Furthermore,the anaerobic digestion process and energy production were evaluated under different organic loading.The results and conclusions were showed as follows.At the start-up stage,the anaerobic digestion was running stably after reactor start-up successfully.The fermentation type was butyric acid type;the use order of VFA in methane production phase showed as follow:ethanol＞butyric acid＞valeric acid＞propionic acid＞acetic acid,the ORP in methane production phase was about -480mV,COD removal was above 80%,solid removal of FVW was 98.6%,the decrement effect of FVW was obvious.However,the anaerobic digestion processing inefficiency caused long digestion time,low removal rate of COD and biogas production.At the low organic loading stage,aiming to improve treatment efficiency,the first stage anaerobic digestion system was optimized by keeping low organic loading and controlling digestion environment.With anaerobic microorganism adapting environment gradually,processing efficiency obtained the enhancement after artificial regulation;anaerobic digestion system was running well on low organic loading,respectively,the solid removal of FVW was above 87%,the largest biogas production and biogas production per influent concentration COD can reach 35L/d and 0.44L/gCOD respectively,percentage of methane was above 50%.The COD removal rate and effluent concentration of COD can reach 70%～80%and 70mg/L.At high organic loading stage and energy production,the buffering capacity was improved,pre-acidification was shorted,and the removal efficiency and biogas yield were increased in digester after enhancing the digestion efficiency in second stage experiment.The maximum organic loading of digester can reached 9gCOD/L·d.With the organic loading being increased,the removal concentration of COD and biogas yield were increasing gradually,and tended to stably after 7.2gCOD/L·d.Meanwhile,the largest biogas production,biogas production per influent COD concentration and biogas production per degradable COD concentration reached 200L/d,0.7L/gCOD and 0.56L/gCOD respectively,with about 70%of methane content and 5g/L·d of removal rate of COD in anaerobic digestion process of FVW.