Biocathodic nitrous oxide removal in bioelectrochemical systems

Area of Science:

• Environmental Science
• Biotechnology
• Electrochemistry

Background:

• Anthropogenic nitrous oxide (N2O) emissions are increasing, contributing significantly to global warming and ozone depletion.
• Current N2O mitigation strategies rely on physicochemical technologies, with no biological treatment options available for point sources.
• N2O is a powerful greenhouse gas with a global warming potential approximately 300 times that of carbon dioxide.

Purpose of the Study:

• To investigate the efficacy of a bioelectrochemical system (BES) utilizing an autotrophic denitrifying biocathode for N2O removal.
• To demonstrate the feasibility of a biological approach for mitigating N2O emissions from industrial sources.
• To establish proof of concept for long-term, cost-effective N2O reduction using microbial catalysts.

Main Methods:

• A bioelectrochemical system (BES) was designed with a biocathode capable of autotrophic denitrification.
• The system was operated for over 115 days, using N2O as the sole electron acceptor.
• Cathode potential was optimized, ranging from -200 to 0 mV vs standard hydrogen electrode (SHE), to maximize N2O conversion rates.

Main Results:

• High N2O removal rates were achieved, ranging from 0.76 to 1.83 kg N m(-3) net cathodic compartment (NCC) d(-1).
• N2O removal rates were directly proportional to current production, with near 100% cathodic coulombic efficiencies.
• Microorganisms were identified as catalysts for N2O reduction to N2, with optimal performance at -200 to 0 mV vs SHE.

Conclusions:

• The study presents the first proof of concept for biocathodic N2O removal over an extended period.
• The BES demonstrated sustainable operation, indicating that N2O respiration provides sufficient energy for the biological process.
• This biological treatment offers a promising, cost-effective, and environmentally friendly alternative to conventional N2O mitigation technologies.