dc.description.abstract | The increasing concern over the energy resource depletion, pollution and global warming has prompted the interest in renewable bioenergy. The anaerobic digestion of organic solid wastes, such as cattle slurry, agricultural wastes, and wastewater treatment sludge, has been well practiced. Co-digestion could become an attractive alternative to traditional single-substrate based digestion for the production of biogas. To explore the digestion characteristics of organic-wastes-to-energy, this study investigated the digestion of single substrate (i.e., sugar, protein, and lipids, respectively), and a mixed substrate (i.e., milk).
In the preliminary work, the process-governing factors (i.e., fermentation temperature, substrate concentration, initial pH values, and concentrations of NH4Cl, KH2PO4, and NaCl) were screened by experiments with an experimental factorial design of Taguchi method, using sewage treatment sludge as starting substrates and cow dung as inoculum. Based on the results of the preliminary work, the fermentation characteristics for hydrogen and methane production was investigated using glucose, casein, linoleic acids, and milk as substrate, respectively. The results indicate that, in hydrogen production, the conversion rate for hydrogen (i.e., milligram hydrogen per gram of substrate) was found to be approximately 3% for glucose substrate, 0.1% for casein, 0.4% for linoleic acids, and 0.9% for mixed substrate, milk. On the other hand, in methane production, the conversion rate for methane (i.e., milligram methane per gram of substrate) was found to be approximately 2% for casein, 0.7% for linoleic acids, and 24% for milk. In the case of linoleic acids substrate, it appeared that the methane production had undergone inhibition by the substrate itself at higher concentration. The results of this study may be of interest to researchers attempting to recovery bioenergy by anaerobic fermentation from mixed organic wastes.
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