Design and evaluation of a novel two-phase partitioning bioreactor to enhance methane mass transfer

Abstract

Background

Methane is typically used in combustion reactions for energy generation or as a disposal strategy. The latter is an environmentally unsustainable practice that demands alternative utilization strategies to convert methane into high-value products. Bioconversion is a responsible methane conversion practice that utilizes bacteria to directly metabolize methane. However, due to mass transfer limitations, widespread adoption of this technology is limited. Thus, a novel two-phase partitioning bioreactor (TPPB) was constructed to improve methane transport through a circulating non-aqueous phase (NAP). Silicone, mineral, and soybean oils were tested abiotically for their suitability as NAPs by evaluating methane volumetric mass transfer coefficients (k_La) at different circulation flow rates (0.25–1.50 L/min).

Results

Due to emulsion formation at higher circulation rates, soybean oil was only tested at 0.25–1.00 L/min, which showed insignificant k_La improvement. For mineral oil, the circulation rate significantly improved the average methane k_La from 9.46 h⁻¹ (0.25 L/min) to 20.44 h⁻¹ (1.5 L/min). Conversely, silicone oil showed the highest significant k_La improvement when the circulation flow rate increased from 0.5 L/min (k_La = 9.93 ± 1.77 h⁻¹) to 1.25 L/min (k_La = 49.24 ± 3.04 h⁻¹). Compared to direct gaseous methane bubbling, 1.25 L/min silicone oil provided a 900% k_La enhancement per unit mass flow of methane fed into the TPPB.

Conclusion

This study demonstrated that TPPB with circulating NAP can provide significantly higher methane k_La than direct methane injection. Although the present study focused solely on abiotic evaluation, the TPPB could prove beneficial in advancing the bioconversion of methane into useful materials. © 2025 Society of Chemical Industry (SCI).