## 5 Application of eNO\({}_{3}\)R to Brackish Groundwater: A Case Study
### Sustainability Analysis  
As previously discussed, electrocatalytic nitrate reduction (eNO\({}_{3}\)R) processes are gaining attraction as alternative processes for the removal of nitrate from various water effluents, including wastewater and groundwater [232]. Indeed, the main reason for this is that these techniques are regarded as environmentally friendly and efficient approaches. Nonetheless, the main stumbling blocks to implementing these technologies on an industrial scale are energy consumption and cost [232; 233; 234]. Thus, renewable energies (RE), particularly solar energy, are seen as an alternative to conventional electricity, as they could convert these processes into truly sustainable, eco-friendly, and autonomous technologies, as well as lessen the environmental impacts related to fossil energy [232; 235]. In fact, solar energy can be mobilized to power the electrochemical cells employed in nitrate reduction, which on the one hand will lead to an increase in the NH\({}_{3}\) faradaic efficiency, and on the other hand, reduce reliance on non-renewable energy sources and subsequently decrease the overall carbon footprint. In this context, [PERSON] et al. [236] harnessed solar energy for the NO\({}_{3}^{-}\) electroreduction to NH\({}_{3}\) using oxide-derived Co as the catalyst. As a result, they attained a high NH\({}_{3}\) faradaic efficiency of 92.37 \(\pm\) 6.7% current density of 565.26 mA.cm\({}^{-2}\) at \(-\)0.8 V vs. RHE, and a high solar-to-fuel efficiency of 11%. Furthermore, hybrid energy systems that couple solar power with other renewable sources like wind or hydroelectric power could guarantee a more consistent and reliable energy source, thus overcoming the intermittency problems inherent in solar power alone. Additionally, energy storage solutions including batteries or supercapacitors can also boost system stability and effectiveness, maintaining continuous operation during times when solar power is unavailable [232]. The integration of solar and wind RE enhances the environmental and sustainability aspects of electrochemical processes but can also have adverse environmental impacts. For instance, water and land use, habitat loss, and the use of harmful materials in manufacturing  
Figure 18: **(a)** Preliminary techno-economic analysis considering only the electricity cost required to produce ammonium nitrate from NO\({}_{3}^{-}\) based on a given price of electricity, cell efficiency, and total cell potential applied. The brown region shows USDA data for the cost of ammoniumnitrate from 2004 to 2014, with the average cost per metric ton in this period as an inset brown dashed line [230]. **(b)** Electric energy cost as a function of energy-related parameters and unit renewable energy cost [231]. **(c)** Energy-related parameters and the corresponding electric energy cost as a function of NO\({}_{3}^{-}\) concentration [231]. can be viewed as potential negative effects in the case of photovoltaic (PV) solar panels [237]. Similarly, the deployment of wind turbines can lead to the depletion or degradation of habitat for wildlife, fish, and plants. Rotating turbine blades can also pose a threat to flying wildlife, and cause \"noise pollution\" [238]. Whilst many studies have documented these environmental impacts, it remains the case that renewable energies contribute to reducing conventional energy consumption and carbon emissions, as well as supporting local development [239; 240]. It is, therefore, vital to carry out life cycle assessment (LCA) studies to list and evaluate all potential environmental impacts, so as to be able to draw up an in-depth action plan to reduce the harmful impacts listed above and take advantage of the positive points of implementing renewable energies. In parallel, a Life Cycle Assessment of electrocatalytic nitrate reduction is essential to fully assess its environmental sustainability.