## Results and Discussions
### Carbon Footprint of the Selected Alternatives  
After a proper LCI was available for each individual case of production of FA, the CF calculations were accomplished with the values of the resources obtained in each alternative. It is worth mentioning that no direct emissions from the ER process are considered. Also, it must be highlighted that the CF calculation was run only for the A1.1, A1.2, and A1.3 alternatives, as the CF values for A\({}_{\text{CONV}}\) and A\({}_{\text{ICR}}\) were provided by the corresponding references [6; 7; 27]. Ecoinvent database was used to obtain the CO\({}_{2}\) equivalent emissions for the requested resources such as conventional FA production, H\({}_{2}\)O, H\({}_{2}\), O\({}_{2}\), and steam [27], and the CO\({}_{2}\) equivalent emissions for the requested PV solar energy were based on the results of a previous study [31]. The CO\({}_{2}\) used as feedstock was considered not to contribute to the CF, as all the emissions are allocated to the corresponding main product, which can be electricity in the case of a coal-fired power plant. Figure 3 displays the CF values corresponding to each alternative, considering the next 5 resources: (i) steam for purification; (ii) avoided emissions from the byproduct O\({}_{2}\); (iii) avoided emissions from the byproduct H\({}_{2}\); (iv) electricity as PV solar energy for the reactor, the pumping, and the compression/liquefaction of H\({}_{2}\)/O\({}_{2}\); and, finally, (v) the ionized water as raw material, using a functional unit of 1 kg of FA as reference, considering that the FA is at a concentration of 85% wt. The mass of CO\({}_{2}\) per mass unit of FA was excluded from the use of resources, but in any case, it would represent a value of \(-1\) kg\(\cdot\)kg\({}^{-1}\). The CF of the electrode materials and catalysers were neglected, as their lifetimes were assumed to be long enough. It can be observed that the demand of steam for the purification stage is the main contribution to GHG in all cases. However, there is a noticeable difference between A1.1 and both A1.2 and A1.3. It should be remarked that in the case of A1.1, the concentration of FA in the inlet feed to the distillation column was only 1.6% wt., while in cases A1.2 and A1.3 it was feed to the distillation column a FA concentration of 10% wt. and 21% wt., respectively. The CF values as kg of CO  
Figure 3: CF values for the selected scenarios (functional unit is 1 kg of FA at a commercial concentration of 85% wt). per kg of FA obtained for A1.1, A1.2, and A1.3, were 31.9 kg\(\cdot\)kg\({}^{-1}\), 5.3 kg\(\cdot\)kg\({}^{-1}\), and 1.6 kg\(\cdot\)kg\({}^{-1}\), respectively. The scenarios used for comparison, A\({}_{\text{CONV}}\), and A\({}_{\text{JCR}}\), present CF values of 2.2 kg\(\cdot\)kg\({}^{-1}\) and 0.16 kg\(\cdot\)kg\({}^{-1}\), respectively [7, 27]. Additionally, it was mentioned above that CF of A\({}_{\text{CONV}}\) could decrease up to 2.07 kg\(\cdot\)kg\({}^{-1}\) whether PV solar was supplied to the plant instead of electricity from the production mix. It must be taken into consideration that in the alternative A\({}_{\text{JCR}}\), H\({}_{2}\) needed in the process is supplied by water electrolysis; therefore, in its CF value (0.16 kg\(\cdot\)kg\({}^{-1}\)), there is no explicit mention of the contribution of conventional H\({}_{2}\) production. If a conventional process was used for H\({}_{2}\) production, it would be necessary to add its CF. The CF value, expressed as the mass of CO\({}_{2}\) emitted per kg of H\({}_{2}\) produced, represents a value of 1.7 kg\(\cdot\)kg\({}^{-1}\)[27]. Adding 0.102 kg\(\cdot\)kg\({}^{-1}\) as CF would lead to a total value of 0.26 kg\(\cdot\)kg\({}^{-1}\). The small contribution of hydrogen is related to the use of just 1.38 times the stoichiometric amount of H\({}_{2}\). In the cases of ER, the avoided burdens from the recovery of H\({}_{2}\) and O\({}_{2}\) have only a significant effect on A1.3.