Cumulative Hydrogen Yield Research Articles

Simultaneous production of 2,3-butanediol, ethanol and hydrogen with a Klebsiella sp. strain isolated from sewage sludge

A Klebsiella sp. HE1 strain isolated from hydrogen-producing sewage sludge was examined for its ability to produce H 2 and other valuable soluble metabolites (e.g., ethanol and 2,3-butanediol) from sucrose-based medium. The effect of pH and carbon substrate concentration on the production of soluble and gaseous products was investigated. The major soluble metabolite produced from Klebsiella sp. HE1 was 2,3-butanediol, accounting for over 42–58% of soluble microbial products (SMP) and its production efficiency enhanced after increasing the initial culture pH to 7.3 (without pH control). The HE1 strain also produced ethanol (contributing to 29–42% of total SMP) and a small amount of lactic acid and acetic acid. The gaseous products consisted of H 2 (25–36%) and CO 2 (64–75%). The optimal cumulative hydrogen production (2.7 l) and hydrogen yield (0.92 mol H 2 mol sucrose −1) were obtained at an initial sucrose concentration of 30 g COD l −1 (i.e., 26.7 g l −1), which also led to the highest production rate for H 2 (3.26 mmol h −1 l −1), ethanol (6.75 mmol h −1 l −1) and 2,3-butanediol (7.14 mmol h −1 l −1). The highest yield for H 2, ethanol and 2,3-butanediol was 0.92, 0.81 and 0.59 mol mol-sucrose −1, respectively. As for the overall energy production performance, the highest energy generation rate was 27.7 kJ h −1 l −1 and the best energy yield was 2.45 kJ mol sucrose −1, which was obtained at a sucrose concentration of 30 and 20 g COD l −1, respectively.

Efficient conversion of wheat straw wastes into biohydrogen gas by cow dung compost

Efficient conversion of wheat straw wastes into biohydrogen gas by cow dung compost was reported for the first time. Batch tests were carried out to analyze influences of several environmental factors on biohydrogen production from wheat straw wastes. The performance of biohydrogen production using the raw wheat straw and HCl pretreated wheat straw was then compared in batch fermentation tests. The maximum cumulative hydrogen yield of 68.1 ml H 2/g TVS was observed at 126.5 h, the value is about 136-fold as compared with that of raw wheat straw wastes. The maximum hydrogen production rate of 10.14 ml H 2/g TVS h was obtained by a modified Gompertz equation. The hydrogen content in the biogas was 52.0% and there was no significant methane observed in this study. In addition, biodegradation characteristics of the substrate were also discussed. The experimental results showed that the pretreatment of the substrate plays a key role in the conversion of the wheat straw wastes into biohydrogen by the composts generating hydrogen.