Recovery and reuse of nitrous oxide from wastewater treatment plants – A step towards carbon neutrality

Carbon neutral systems are gaining importance in recent years as a sustainable technology that reduces both carbon and energy footprints. Nitrous oxide (N2O), a greenhouse gas (GHG) with global warming potential of 273 times as that of CO2 equivalents, is generated from all wastewater treatment plants (WWTPs) that undergo biological nitrogen removal. Because of the critical situation imposed by this GHG emission, there has been a dire need to entrap N2O for mitigating uncontrolled release of the gas into the atmosphere. WWTPs cause unintended and uncontrolled emission of N2O, increasing carbon footprint. In the light of the hypothesis of controlling carbon footprint using N2O as fuel, this present article analyses the practical application of the idea and the limiting factors that prevent the technology from being implemented. The article summarizes the concepts of N2O recovery pathways in biological effluent treatment systems, evaluating feasibility for energy generation using N2O as a fuel additive that can have severe negative environmental impacts, if not collected and stored properly. This review also discusses the various models developed to predict N2O emissions from treatment plants, highlighting the areas of further research and investigation required for full-scale application of N2O recovery. The critical review indicates the retrieval of nitrogen as N2O and its reuse would indicate a potential carbon neutral solution for WWTPs treating high strength wastewater, an area yet to be investigated. [Display omitted] •N2O is unintentionally emitted from biological wastewater treatment units.•Recovery of N2O can be used as a fuel-oxidant with CH4 for higher energy generation.•Collection and storage challenges limits the application of this technology.•N2O recovery from high strength wastewater with proper collection can be promising.