Biohydrogen production in an AFBR using sugarcane molasses.

Area of Science:

• Biotechnology
• Environmental Engineering
• Renewable Energy

Background:

• Sugarcane molasses presents a viable substrate for biohydrogen production.
• Anaerobic fluidized bed reactors (AFBRs) offer potential for efficient microbial processes.
• Understanding microbial dynamics is crucial for optimizing biohydrogen yields.

Purpose of the Study:

• To evaluate hydrogen production from sugarcane molasses using an AFBR.
• To determine the optimal hydraulic retention time (HRT) for maximum hydrogen production.
• To analyze the influence of microbial community structure on hydrogen generation.

Main Methods:

• Operation of a 1.2 L AFBR with shredded tires as support material.
• Inoculation using sludge from an upflow anaerobic sludge blanket (UASB) reactor.
• Testing of hydraulic retention times (HRTs) at 12, 6, 4, and 3 hours.
• Analysis of hydrogen production rate, yield, COD removal, carbohydrate conversion, metabolite profiles, and microbial community structure (PCR-DGGE).

Main Results:

• Maximum hydrogen production rate of 1.44 L-H2 h-1 L-1 at 4h HRT.
• Highest hydrogen yield of 3.07 mol-H2 mol-1 glucose at 6h HRT.
• Optimal COD removal (23.3%) at 12h HRT and carbohydrate conversion (70.1%) at 6h HRT.
• Ethanol and acetic acid were primary metabolites, indicating ethanol-type fermentation.
• Microbial community similarity was high between 4h and 3h HRTs, with diversity peaking at 6h HRT.

Conclusions:

• Hydraulic retention time significantly impacts hydrogen production and microbial community structure in AFBRs.
• A 6h HRT appears optimal for balancing hydrogen yield and microbial diversity.
• The study highlights the potential of AFBRs for biohydrogen production from molasses, with microbial diversity playing a key role.