Researchers in China have developed a new fermentation system that boosts biohydrogen production while capturing carbon dioxide.

Researchers from the Institute of Applied Ecology of the Chinese Academy of Sciences revealed that dark fermentation produces hydrogen gas from organic substrates under oxygen-free conditions, making it a promising route toward carbon-neutral hydrogen.

The team introduced wollastonite as a dual-function agent to simultaneously enhance H2 yield and capture CO2. “An optimal dosage of 10 g/L was identified, which shortened the lag phase from 23.13 to 12.38 h and increased the hydrogen yield from 158.11 ± 3.44 mL/g glucose-consumed to 210.75 ± 15.87 mL/g glucose-consumed,” said researchers in the study.

“Mechanistically, wollastonite buffered the system pH, steering metabolic flux away from lactate towards acetate synthesis by enriching Clostridium and suppressing Lactobacillus.”

Wollastonite (CaSiO3) is a naturally occurring silicate mineral and researchers used it as a dual-function additive.

As acids accumulate during fermentation, they gradually dissolve the mineral, consuming protons and releasing calcium ions. This mechanism provides continuous, self-regulating pH buffering that stabilized the system at pH 6.5–7.0. At an optimal dosage of 10 g/L, the lag phase of hydrogen production decreased by about 50%, and the specific hydrogen yield increased by roughly 33%, according to researchers.

“Wollastonite also enabled in-situ CO2 sequestration by precipitating it as CaCO3. However, maximal CO2 capture was achieved at a higher dosage (≥15 g/L), which passively reached the required neutral pH but compromised the hydrogen yield. This created a conflict with the optimal 10 g/L dosage for hydrogenesis,” said researchers in the study published in the Chemical Engineering Journal.