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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 bioH production followed the order WD > MSD > DWP. The bio-H 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. BioH 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 H 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 H generation as the value-added product. Research is ongoing to increase the yield of biohydrogen production from waste disposable diapers.

Waste with high biomass content generated in cities in developing countries is sent to landfills or open dumps. This research aims to degrade biomass content in urban waste through cultivation, at pilot scale, of the edible mushroom Pleurotus ostreatus. First, the number of diapers used by one baby per week was measured with a survey in day care facilities. Then, cellulose content of diapers was assessed. Finally, cultivation of P. ostreatus was carried out using as substrate a mixture of diapers with gardening waste, a co-substrate readily available at urban settings. The factors assessed were strain of P. ostreatus (grey BPR-81, white BPR-5), conditioning of the substrate (diapers with and without plastic) and co-substrate (wheat straw, grass, and withered leaves). Results show that diapers are a OPEN ACCESSSustainability 2015, 7 6034 valuable source of biomass, as generation of diapers with urine is 15.3 kg/child/month and they contain 50.2% by weight of cellulose. The highest reductions in dry weight and volume (>64%) of substrates was achieved with the substrate diaper without plastic and co-substrate wheat straw. Although diapers with plastic and grass and leaves showed lower degradation, they achieved efficiencies that make them suitable as a co-substrate (>40%), considering that their biomass is currently confined in landfills.

Absorbent hygiene products (AHP) have received much interest due to the notion that their end-of-life (EoL) stage has high environmental impacts. Since the use of AHP will continue to rise in the foreseeable future, information that helps with a reduction in the environmental impacts of AHP through their life cycle is needed. This research presents an estimation of AHP in municipal waste, and it also reviews and discusses waste management options, available treatments at bench, pilot or full scale, and life cycle assessments (LCAs) available in the literature. Municipal waste of countries belonging to the Organization for Economic Co-operation and Development contains on average 2.7% of baby nappies, 4.8% of adult nappies and 0.5% of sanitary pads (in weight), whereas that of Latin-American countries have 7.3%, 3.3%, and 0.9%, respectively. Management options for AHP waste in developed countries are landfilling and incineration, while in developing countries AHP are disposed of in dumpsites and landfills. Most LCAs identify significant environmental impacts in the production of raw materials, while EoL scenarios involving incineration and landfill were found to have a significant contribution to global warming potential. Substitution with alternative products has been suggested as a way of decreasing environmental impacts; however, their use frequently causes a trade-off on different impact categories. Municipalities could use a wide range of policy tools, such as extended producer responsibility systems, bans, levies, ecolabelling, or a combination of these, to reduce the environmental and economic burden of AHP waste.

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