## 5 Application of eNO\({}_{3}\)R to Brackish Groundwater: A Case Study
### Economic Analysis  
Most publications in nitrate removal by electrocatalysis focus on the performance of electrode material but rarely discuss capital expenditures (CAPEX) and operational expenditures (OPEX). However, it is obvious that since the process is still in the R&D phase, significant steps remain before industrial application, such as the construction of efficient reactors [226]. Nonetheless, this does not dismiss the importance of making estimates to determine whether the process is economically viable or not. Generally, 90% of synthetic ammonia is produced using the Haber-Bosch process, but there are other methods such as electrocatalytic and photocatalytic N\({}_{2}\) reduction. Therefore, eNO\({}_{3}\)R remains innovative compared to existing methods [227; 228]. The comparison between energy consumption and energy source for the different processes shows that eNO\({}_{3}\)R is the most promising due to the total energy demand during the process. Furthermore, the possibility of using solar energy remains a strong point of the process. The production cost of ammonia by the Haber-Bosch process is $560 per metric ton, which is close to the estimated value for production by eNO\({}_{3}\)R in the case of using the strained ruthenium nanocluster ($776 per metric ton) [229]. Additionally, [PERSON] et al. [230] conducted an economic study based on NH\({}_{4}\)NO\({}_{3}\) as the final product instead of NH\({}_{3}\). They validated the production of this type of fertilizer at a cost that matches or is lower than the typical United States Department of Agriculture (USDA) cost range for NH\({}_{4}\)NO\({}_{3}\). Nonetheless, strictly with low electricity costs and reasonable Faradaic efficiencies (Figure 18) [230]. On the other hand, the techno-economic analysis by [PERSON] et al. [231] confirmed the relationship between the energy cost per kilogram of (NH\({}_{4}\))\({}_{2}\)SO\({}_{4}\) and the Faradaic efficiency/energy consumption. They also emphasized that the concentration of nitrates in effluents plays a crucial role in minimizing costs. So, a high concentration of 1.0 M nitrate found in wastewater is preferable to 0.01 M  
Figure 17: Schematic representations of (**a**) the flow cell with porous electrode for nitrate reduction to ammonia [20]. (**b**) Electrochemical continuous flow system with copper as cathode and DSA as anode [221]. (**c**) The flow-through electrocatalytic system for nitrate reduction with the zero-gap electrochemical reactor [225]. (**d**) Schematic diagram of the pilot-scale electrochemical reactor [222].  
found in some brackish groundwater to minimize the cost of ammonia production [231]. Overall, eNO\({}_{3}\)R for ammonia or even fertilizers production has potential economic benefits and is a promising candidate to replace the Haber-Bosch process specifically for high concentrated nitrate contaminated water. Regarding the concentration of nitrate in brackish groundwater, it is preferable to convert it to gaseous nitrogen, which is economically viable. However, the cost of electrode materials and energy consumption are critical to the application of this process. So far, there have been no economic analyses of this process because it is still in the stage of researching selective materials. However, it is essential to consider the cost of the materials used in the process, focusing on non-noble or non-metallic materials in future research to compete with existing processes.