Reports from the Frontier: Electrifying Chemical Transformations and Separations to Valorize Wastewater Nitrogen

Ammonia is an essential compound to modern society, underpinning fertilizer production and chemical manufacturing. Global ammonia demand currently exceeds 150 million tons a year and is projected to increase over 2% annually. Over 96% of ammonia is currently generated through the Haber-Bosch (HB) process, in which steam-reformed hydrogen reacts with nitrogen under reaction conditions that consume 1-2% of global energy and contribute 1.2-1.4% of anthropogenic CO2 emissions every year. In an environmental context, ammonia is a form of reactive nitrogen. Large amounts of reactive nitrogen, such as HB ammonia, accumulate in the biosphere because 80% of wastewater globally is discharged without treatment. The resulting skew in the global nitrogen cycle leads to imbalanced ecosystems and threatens water quality. Conventional water treatment removes reactive nitrogen by converting it to N2 (biological nitrification-denitrification); at HB facilities, the N2 is then cycled back to produce ammonia. Directly valorizing reactive nitrogen in waste streams would shortcut the use of N2 as an intermediate in water remediation and ammonia production, allowing savings in energy, emissions, and costs. Indeed, treating nitrogen as a resource to recover rather than simply a pollutant to remove aligns with the US National Academy of Engineering's call to manage the nitrogen cycle, a challenge central to chemical manufacturing and ecosystem protection.

Automated summary

Ammonia is an indispensable compound for modern society, playing a crucial role in fertilizer production and chemical manufacturing. The global demand for ammonia currently exceeds 150 million tons per year and is expected to grow by over 2% annually. The majority of ammonia production, about 96%, is achieved through the energy-intensive Haber-Bosch process, resulting in significant energy consumption and anthropogenic CO2 emissions. The accumulation of reactive nitrogen, particularly from untreated wastewater, disrupts the global nitrogen cycle, leading to imbalanced ecosystems and water quality issues. Finding ways to directly utilize reactive nitrogen in waste streams can offer substantial energy, emission, and cost savings, aligning with the goal of managing the nitrogen cycle and protecting ecosystems.