# Reverse Electrodialysis: Potential Reduction in Energy and Emissions of Desalination
## Appendix B Global Warming Potential Metric's Definition  
Equation (A4) defines the desalination plant's 100-year Global Warming Potential (GWP\({}_{100}\)) per cubic meter of desalted water in the BaU (Share = 0) and the Mix+RED energy supply scenarios:  
\[\mathrm{GWP_{100}}\left(\mathrm{kg\;CO_{2}-eq\;m^{-3}}\right)=\left[(1-\mathrm{ Share})\;\mathrm{GWP_{100,\;mix}}+\mathrm{Share\;GWP_{100,\;RED}}\right]\;\mathrm{SEC}\] (A4)  
\[\mathrm{Share}=\mathrm{SE/SEC}\] (A5)  
where GWP\({}_{100,\;mix}\) is the local grid mix GWP\({}_{100}\) per unit of electricity produced as specified in IPCC 2013 impact assessment method (retrieved from the ecoinvent database version 3.6 [65]), GWP\({}_{100,\;red}\) is the RED plant's GWP\({}_{100}\) in \"current\" or \"optimistic\" energy supply scenarios (kg CO\({}_{2}\)-eq kWh\({}^{-1}\)), SE is the RED's specific energy supply (Net Specific Energy or Specific Retrieved Exergy in the \"current\" or \"optimistic\" energy supply scenarios) in kWh per cubic meter of desalted water, and SEC is the desalination plant's Specific Energy Consumption (kWh m\({}^{-3}\)).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Geography** & **Fossil Fuels 1** & **Hydro** & **Nuclear** & **Renewables 2** & **Waste** & **Scenario** \\ \hline United Arab Emirates (AE) & 99.8\% & - & - & 0.2\% & - & 6 \\ Australia (AU) & 87.1\% & 6.8\% & - & 6.1\% & - & 18, 20 \\ Bahrain (BH) & 100\% & - & - & - & - & 1 \\ Chile (CL) & 62.2\% & 33.9\% & - & 3.9\% & - & 5 \\ China & 78.2\% & 16.7\% & 2.0\% & 3.0\% & - & 14 \\ Curacao (CW) & 46.4\% & - & - & 53.6\% & - & 12 \\ Algeria (DZ) & 99.5\% & 0.4\% & - & 0.1\% & - & 3 \\ Spain (ES) & 32.5\% & 16.4\% & 26.6\% & 24.4\% & 0.1\% & 2, 11 \\ Gibraltar (GI) & 100\% & - & - & - & - & 8 \\ Israel & 100\% & - & - & - & - & 17 \\ India (IN) & 82.7\% & 10.5\% & 2.9\% & 3.9\% & - & 13 \\ Japan (IP) & 86.6\% & 8.9\% & 2.0\% & 1.0\% & 1.5\% & 7 \\ Mexico (MX) & 81.0\% & 11.4\% & 4.1\% & 3.4\% & - & 10 \\ Saudi Arabia (SA) & 100\% & - & - & - & - & 9, 15 \\ Singapore (SG) & 96.7\% & - & - & 0.5\% & 2.7\% & 16 \\ United States (US) & 64.6\% & 7.4\% & 20.1\% & 7.5\% & 0.4\% & 4, 19 \\ \hline \hline \end{tabular} 1
[FOOTNOTE:1]Footnote 1: Hard coal; lignite; industrial gases; oil; natural gas. 2
[FOOTNOTE:2]Footnote 1: Hard coal; lignite; industrial gases; oil; natural gas. 2  
\end{table}
Table 1: Local electricity supply mix including imports. Data from [65].  
The GWP\({}_{100}\) per kWh of a RED plant with N\({}_{\text{p}}\) parallel trains each with N\({}_{\text{s}}\) series RED units was computed as follows:  
\[\text{GWP}_{100,\text{ RED}}\left(\text{kg CO}_{2}-\text{eq kWh}^{-1}\right)= \frac{\text{N}_{\text{s}}\,\text{N}_{\text{p}}\,\text{GWP}_{100,\text{ RED}}\,\text{stack}}{\text{E}_{\text{plant}}\, \text{LT}} \tag{10}\]  
where GWP\({}_{100,\text{ RED}}\) stack is the GWP of the RED stack (kg CO\({}_{2}\)-eq) as defined in [PERSON] et al.'s LCA [66], and E\({}_{\text{plant}}\) and LT are the retrieved exergy yield or net energy yield (kWh year\({}^{-1}\)) and the lifetime (20 years) of the RED plant, respectively.  
The annual energy yield of a RED plant working at full capacity--i.e., 8760 full load hours per year (FLH)--is given by:  
\[\text{E}_{\text{plant}}\left(\text{kWh year}^{-1}\right)=\left(\text{N}_{\text {p}}\sum_{i=1}^{\text{N}_{\text{s}}}\text{P}_{i}\right)\text{FLH} \tag{11}\]  
where P\({}_{i}\) is the capacity of each series RED unit (Table 2) under operating conditions reported in Table 3, either in \"current\" (net power) or \"optimistic\" (retrieved exergy flow) energy supply scenarios (kW).