Abstract In the present work, an innovative approach of used disposable nappies (DN) treatment is presented aiming at energy recovery through anaerobic co-digestion of their biodegradable content along with a… Click to show full abstract
Abstract In the present work, an innovative approach of used disposable nappies (DN) treatment is presented aiming at energy recovery through anaerobic co-digestion of their biodegradable content along with a waste fraction containing expired food products (EFP). More specifically, a mixture of hydrolysate, prepared from used disposable nappies with pulverized fruits/vegetables that have lost their retail value, was used as feedstock in two- and one-stage mesophilic anaerobic digestion systems at a 60:40 (v/v) ratio. For the two-stage experiments, different combinations of pH and Hydraulic Retention Time (HRT) were tested in the acidogenic and methanogenic reactor. The performance of the system, operated at steady-state conditions, in terms of COD removal, digestion stability, and biofuels (H2 and CH4) production, was compared with that obtained from the one-stage configuration. The comparison between the two systems revealed that COD removal reached 80% in the two-stage system, but only 68% in the one-stage. At HRT 25d the yield of produced methane in the methanogenic reactor of the two-stage system reached the theoretical value of 0.35 LCH4/gt-COD removed. Comparing the two-stage system, operated at HRT 15d, with the one-stage system, it was evident that the energy production of the two-stage system was higher by 18.4%.
               
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