Hydrogen production with effluent from an ethanol-H2-coproducing fermentation reactor using a single-chamber...

Area of Science:

• Biotechnology
• Renewable Energy
• Environmental Science

Background:

• Bacterial fermentation of sugars is a known method for hydrogen production.
• However, this process often results in incomplete substrate conversion and lower hydrogen yields.

Purpose of the Study:

• To investigate the potential of enhancing hydrogen production from fermentation effluent.
• To evaluate the effectiveness of a single-chamber microbial electrolysis cell (MEC) in conjunction with dark-fermentation.

Main Methods:

• Utilized a single-chamber microbial electrolysis cell (MEC) fed with effluent from an ethanol-type dark-fermentation reactor.
• Investigated the impact of buffered (pH 6.7-7.0) and unbuffered effluent on MEC performance.
• Assessed hydrogen production rates, recovery, and electrical energy efficiency at varying applied voltages (0.5-0.8 V).

Main Results:

• Buffered fermentation effluent in the MEC achieved an 83% hydrogen recovery and a production rate of 1.41 m(3) H(2)/m(3)/d at 0.6 V.
• Integrating the MEC with the fermentation system yielded 96% overall hydrogen recovery and a production rate of 2.11 m(3) H(2)/m(3)/d, with 287% electrical energy efficiency.
• MEC performance was critically dependent on buffering the effluent; unbuffered effluent resulted in minimal hydrogen production.

Conclusions:

• Microbial electrolysis cells (MECs) can significantly increase hydrogen yields from bacterial fermentation processes.
• Buffering the fermentation effluent is essential for optimal MEC performance and efficient biohydrogen generation.
• This combined approach offers a promising strategy for enhanced sustainable hydrogen production.