## Results and Discussions
### Carbon Footprint of the Selected Alternatives
Values displayed in Figure 3 present positive values due to those resources positive CF contributions and negative values from the avoided H\({}_{2}\) and O\({}_{2}\). As it was mentioned, the ER of CO\({}_{2}\) to FA has also a positive effect in terms of environmental sustainability: a reduction in the consumption of raw materials is also expected. An assessment of the amount of raw materials needed was carried out in the A\({}_{\text{CONV}}\), A\({}_{\text{JCR}}\), and A1.3 scenarios. Table 4 shows the quantities of raw materials needed for the production of 1 kg of FA. For a fair comparison, electricity was assumed to be obtained from renewable energy in all scenarios. While for A\({}_{\text{CONV}}\) scenario, direct figures of heavy oil and natural gas were provided, data for A\({}_{\text{JCR}}\) scenario were derived based on the heating needs obtained from liquefied natural gas (LNG) combustion (54.40 MJ\(\cdot\)kg\({}^{-1}\)) [32]. From the point of view of natural resources consumption and their environmental implications, as in the case of conventional fossil fuel utilization, the conventional/commercial fabrication of FA used as benchmark presents higher consumption of natural gas and heavy fuel oil in comparison with both A1.3 and A\({}_{\text{JCR}}\) alternatives. Conventional production of 1 kg FA requires the consumption of natural gas for heating purposes of 0.246 kg\(\cdot\)kg\({}^{-1}\), which is in the same order of magnitude than the values of natural gas for heating of both A\({}_{\text{JCR}}\) and A1.3. However, it must be taken into account that the conventional FA route of hydrolysis of methyl formate, which is obtained by carbonylation of methanol, involves a second consumption of natural gas at high pressure for production of the methanol [27]. This additional consumption of natural gas per kg of FA represents an overall consumption of natural gas higher than both CO\({}_{2}\) valorisation options. In addition, conventional production of 1 kg of FA from MeOH and CO involves a consumption of catalysts per unit of mass of FA of 15.6 \(\times\) 10\({}^{-6}\) kg\(\cdot\)kg\({}^{-1}\) (such as aluminium oxide, copper oxide, molybdenum, nickel, and zinc) as sourced from Ecoinvent data [27]. In the A\({}_{\text{JCR}}\) scenario, 3.75 \(\times\) 10\({}^{-6}\) kg of ruthenium and phosphine-based catalysts are reported to be consumed per kg of FA produced [7]. In the case of A1.3, 14.88 \(\times\) 10\({}^{-6}\) kg of catalysts are needed for the production of 1 kg of FA. Alternative A\({}_{\text{JCR}}\) needs 0.060 kg of H\({}_{2}\) per kg of FA that is produced. In the study, it was assumed that H\({}_{2}\) came from an in-situ electrolyser. However, in a worst scenario, hydrogen would be produced conventionally at refineries by (i) steam reforming of light ends or natural gas (the most common production route in Europe); (ii) partial oxidation (gasification) of heavy oil fractions (produces syngas, from which hydrogen can be separated; and (iii) coal or coke gasification, representing additional fossil fuel consumption in the alternative A\({}_{\text{JRC}}\). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{6}{c}{**Raw Materials Consumption**} \\ \hline  & **Unit** & **A\({}_{\text{CONV}}\)**[27] & **A1.3** & **A\({}_{\text{JCR}}\)** \\ \hline Heavy fuel oil & kg & 0.405 & & & \\ Natural gas (_heat_) & kg & 0.273 & 0.423 & 0.166 \\ Natural gas at high pressure 1  & kg & 1.250 & & & 0.060 ** \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Consumption of raw materials (per unit of kg of FA).