Biohydrogen production from used diapers: Evaluation of effect of temperature and substrate conditioning

This research assessed the viability to use disposable diapers as a substrate for the production of biohydrogen, a valuable clean-energy source. The important content of cellulose of disposable diapers indicates that this waste could be an attractive substrate for biofuel production. Two incubation temperatures (35 °C and 55 °C) and three diaper conditioning methods (whole diapers with faeces, urine, and plastics, WD; diapers without plastic components, with urine and faeces, DWP; diapers with urine but without faeces and plastic, MSD) were tested in batch bioreactors. The bioreactors were operated in the solid substrate anaerobic hydrogenogenic fermentation with intermittent venting mode (SSAHF-IV). The batch reactors were loaded with the substrate at ca. 25% of total solids and 10% w/w inoculum. The average cumulative bioH₂ production followed the order WD > MSD > DWP. The bio-H₂ production using MSD was unexpectedly higher than DWP; the presence of plastics in the first was expected to be associated to lower degradability and H2 yield. BioH₂ production at 55 °C was superior to that of 35 °C, probably owing to a more rapid microbial metabolism in the thermophilic regime. The results of this work showed low yields in the production of H₂ at both temperatures compared with those reported in the literature for municipal and agricultural organic waste. The studied process could improve the ability to dispose of this residue with H₂ generation as the value-added product. Research is ongoing to increase the yield of biohydrogen production from waste disposable diapers.