Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1277482 | International Journal of Hydrogen Energy | 2013 | 9 Pages |
•Enhanced HY was observed when CS co-digested with different wastes.•CES was the optimal co-substrate and the HY increased 46% due to its addition.•Enhanced pH buffer capacity was demonstrated to be the most critical influence.•Co-substrates addition improved carbohydrate/protein ratio, C:N and C:P ratios.•PCR-DGGE showed co-substrates addition enriched the hydrogen-producing bacteria.
In this study, an efficient strategy to increase the hydrogen yield from cassava stillage (CS), by its co-digestion with organic wastes, was developed. The effects of different co-substrates on hydrogen yield were evaluated and compared, with increases obtained in all co-digestion reactors. The maximal hydrogen yield was achieved by CS co-digestion with cassava excess sludge (CES), which resulted in a 46% increase over the yield from CS alone. Improved hydrolysis and acidification performances, and thus increased hydrogen production, were additional benefits of co-digestion, especially with CES. Also, the presence of a co-substrate promoted butyrate over lactate generation. The most influential advantage of co-substrate addition was the enhanced pH buffering capacity, which correlated linearly with hydrogen yield (R2 = 0.98). Moreover, the co-substrates addition resulting in more favorable carbohydrate-COD/protein-COD ratio, C/N and C/P ratios, all of which also correlated linearly with hydrogen yield (R2 = 0.86, 0.71, and 0.75 respectively). Polymerase chain reaction–denaturing gradient gel electrophoresis analysis of the role of microorganisms indicated that the addition of even small amounts of co-substrate altered the bacterial communities within the reactors, enriching the proportion of hydrogen-producing bacteria. A species detected only in the co-digestion reactors was shown to be related to Clostridium cellulosi, which is an efficient hydrogen-producer, while some bacteria not involved in hydrogen production and present in the CS alone reactor were not detectable in any of the co-substrate-containing reactors.