Maximizing the potential of biohydrogen production through cyclic photo fermentation: An approach towards zero waste

The present study aims to investigate the potential of recycled corn stover (CS) residues from photo fermentative biohydrogen production (PFHP) reactors for further cycles to evaluate its PFHP potential. Results showed hydrogen generation yields of 70.32, 63.95, and 16.73 mL/g in the 1st, 2nd, and 3rd cycles respectively which confirms that PFHP in cyclic systems produces approximately twice as much hydrogen as in a single cycle. Total intermediate by-products of 2.59 g/L (19 % and 197 % higher) at 24 h indicate that hydrogen production follows the acetic acid and butyric acid pathway in the first cycle. Thermogravimetric analysis (TGA) showed that solid residues of 1st FR, 2nd FR, 3rd FR, and CS were 12.03 %, 13.02 %, 27.93 %, and 34.55 % respectively. The energy, and light conversion efficiency (ECE, LCE) of cyclic PFHP was 1.16, and 1.15-fold higher than the first cycle, consequently, the present research offers a novel way to maximize CS's potential for PFHP with minimal waste. The experimental findings of the present study revealed that recovered residues from the fermentative bioreactors can be further utilized to enhance the overall biohydrogen production yield which not only minimizes the waste generation but also helps to reduce the cost of pre-treatment in subsequent cycles of biohydrogen production.