COMSOL software was used for the modeling of the performance parameters of the Molten Carbonate -Lignin Fuel Cell (MC-LFC), as it is a flexible tool, able to handle different physical approaches. The model developed includes the following processes: electronic and ionic charge balance (Ohm's law), Butler-Volmer charge transfer kinetics, diffusion gas flow in porous electrodes (Brinkman's equation), gas-phase mass balances in fuel and oxygen distribution channels, and porous electrodes (Maxwell-Stefan diffusion and convection). A parametric analysis was performed to evaluate the effect of material properties, pressure, and temperature, on cell performance. The results show that for a better performance of the MC-LFC cell, the exchange current density (A/m 2 ) in the anode and cathode compartment must be respected in the interval [0.075, 0.75] and [1.58, 15.8]. The electrical conductivity of the electrolyte (S/m), anodic and cathodic materials can be respectively in the interval [26, 265], [25, 250], and [19, 60]. It is also noted that the increase in temperature from 700 K to 1000 K generates a drop in the maximum power density of the battery (approximately 1500 mW/cm 2 to 1260 mW/cm 2 ). It is in every interest to operate the Cell MC-LFC under 500 °C.

The most studied Molten Carbonate-Direct Carbon Fuel Cel (MC-LFC) or Molten Carbonate Direct Carbon Fuel Cell (MC-DCFC) prototypes are those which are fed by fossil fuel. Substituting these fossilized fuels in the MC-DCFC operation with lignin, which is a bio-based carbon, may make this system more efficient, clean, and sustainable. The manipulation module (Mixture) and the computational module (Equilib) of the Factsage package were used to simulate two systems that can represent the anodic compartment of a direct carbon fuel cell based on MC-DCFC. The first system includes lignin and a mixture of molten carbonate (Li2CO3-Na2CO3-Cs2CO3). The second system uses the same first electrolyte system but with the addition of CO2 gas. The results show the formation of mixed gases in the anodic compartment which are composed of H2, CO, CO2, CH4 and H2O. The relative concentration of each of the species of this mixed gas has an impact on the efficiency of the MC-DCFC. How the relative concentration of these gases in this electrolyte can impact the performance parameters of the MC-DCFC is systematically analysed. If the operating conditions of the fuel cell are optimized to get a gas composition of mainly of CO2 with low amounts of H2, CO, CH4, H2O in the anode compartment of the MC-DCFC, This will help to improve the conversion efficiency of lignin fuel in the MC-DCFC.