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1. Alternative ammonia production processes and the use of renewables

   https://doi.org/10.1016/B978-0-12-819242-9.00007-5  

   Hochman, Gal; Goldman, Alan S.; Felder, Frank A. (September 2021, Biomass, Biofuels, Biochemicals)

   Murthy, G. S.; Gnansounou, E.; Khanal, S. K.; Pandey, A. (Ed.)

   The Haber–Bosch synthesis of ammonia is an energy-intensive process that uses coal or natural gas as a fuel and feed. Direct electrochemical nitrogen reduction represents a potential alternative to the Haber–Bosch process that can be less polluting. This alternative route to ammonia from dinitrogen is not likely to require the same large capital investments as does the Haber–Bosch process, thus suggesting a distributive production structure of ammonia relative to the existing ammonia industry. In addition, the flexibility borne from the use of electrochemistry yields technologies that are better fit for the use of renewable energy sources that supply intermittent electricity. We show that under certain scenarios, at levels of efficiency (as determined by the required overpotential and the Faradaic efficiency) that might reasonably be achieved, direct electrochemical nitrogen reduction would be a sustainable and economically viable alternative to the Haber–Bosch process. 

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2. A Research Road Map for Responsible Use of Agricultural Nitrogen

   https://doi.org/10.3389/fsufs.2021.660155  

   Udvardi, Michael; Below, Frederick E.; Castellano, Michael J.; Eagle, Alison J.; Giller, Ken E.; Ladha, Jagdish Kumar; Liu, Xuejun; Maaz, Tai McClellan; Nova-Franco, Barbara; Raghuram, Nandula; et al (May 2021, Frontiers in Sustainable Food Systems)

   null (Ed.)

   Nitrogen (N) is an essential but generally limiting nutrient for biological systems. Development of the Haber-Bosch industrial process for ammonia synthesis helped to relieve N limitation of agricultural production, fueling the Green Revolution and reducing hunger. However, the massive use of industrial N fertilizer has doubled the N moving through the global N cycle with dramatic environmental consequences that threaten planetary health. Thus, there is an urgent need to reduce losses of reactive N from agriculture, while ensuring sufficient N inputs for food security. Here we review current knowledge related to N use efficiency (NUE) in agriculture and identify research opportunities in the areas of agronomy, plant breeding, biological N fixation (BNF), soil N cycling, and modeling to achieve responsible, sustainable use of N in agriculture. Amongst these opportunities, improved agricultural practices that synchronize crop N demand with soil N availability are low-hanging fruit. Crop breeding that targets root and shoot physiological processes will likely increase N uptake and utilization of soil N, while breeding for BNF effectiveness in legumes will enhance overall system NUE. Likewise, engineering of novel N-fixing symbioses in non-legumes could reduce the need for chemical fertilizers in agroecosystems but is a much longer-term goal. The use of simulation modeling to conceptualize the complex, interwoven processes that affect agroecosystem NUE, along with multi-objective optimization, will also accelerate NUE gains. 

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

   https://doi.org/10.1149/2.F04232IF  

   Liu, Matthew; Tarpeh, William (June 2023, The Electrochemical Society Interface)

   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. 

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4. Nitrogen management during decarbonization

   https://doi.org/10.1038/s43017-024-00586-2  

   Zhang, Xin; Sabo, Robert; Rosa, Lorenzo; Niazi, Hassan; Kyle, Page; Byun, Jun Suk; Wang, Yanyu; Yan, Xiaoyuan; Gu, Baojing; Davidson, Eric A (October 2024, Nature Reviews Earth & Environment)

   Decarbonization is crucial to combat climate change. However, some decarbonization strategies could profoundly impact the nitrogen cycle. In this Review, we explore the nitrogen requirements of five major decarbonization strategies to reveal the complex interconnections between the carbon and nitrogen cycles and identify opportunities to enhance their mutually sustainable management. Some decarbonization strategies require substantial new nitrogen production, potentially leading to increased nutrient pollution and exacerbation of eutrophication in aquatic systems. For example, the strategy of substituting 44% of fossil fuels used in marine shipping with ammonia-based fuels could reduce CO2 emissions by up to 0.38 Gt CO2-eq yr−1 but would require a corresponding increase in new nitrogen synthesis of 212 Tg N yr−1. Similarly, using biofuels to achieve 0.7 ± 0.3 Gt CO2-eq yr−1 mitigation would require new nitrogen inputs to croplands of 21–42 Tg N yr−1. To avoid increasing nitrogen losses and exacerbating eutrophication, decarbonization efforts should be designed to provide carbon–nitrogen co-benefits. Reducing the use of carbon-intensive synthetic nitrogen fertilizer is one example that can simultaneously reduce both nitrogen inputs by 14 Tg N yr−1 and CO2 emissions by 0.04 (0.03–0.06) Gt CO2-eq yr−1. Future research should guide decarbonization efforts to mitigate eutrophication and enhance nitrogen use efficiency in agriculture, food and energy systems. 

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5. Revealing Mechanisms of Lithium‐Mediated Nitrogen Reduction Reaction from First‐Principles Simulations

   https://doi.org/10.1002/cphc.202401097  

   Zhou, Chengyu; Zhao, Qing (February 2025, ChemPhysChem)

   Abstract Recently, lithium‐mediated nitrogen reduction reaction (Li‐NRR) in nonaqueous electrolytes has proven to be an environmentally friendly and feasible route for ammonia electrosynthesis, revealing tremendous economic and social advantages over the industrial Haber‐Bosch process which consumes enormous fossil fuels and generates massive carbon dioxide emissions, and direct electrocatalytic nitrogen reduction reaction (NRR) which suffers from sluggish kinetics and poor faradaic efficiencies. However, reaction mechanisms of Li‐NRR and the role of solid electrolyte interface (SEI) layer in activating N₂remain unclear, impeding its further development. Here, using electronic structure theory, we discover a nitridation‐coupled reduction mechanism and a nitrogen cycling reduction mechanism on lithium and lithium nitride surfaces, respectively, which are major components of SEI in experimental characterization. Our work reveals divergent pathways in Li‐NRR from conventional direct electrocatalytic NRR, highlights the role of surface reconstruction in improving reactivity, and sheds light on further enhancing efficiency of ammonia electrosynthesis. 

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