Alternative routes of the MixAlco® process, i.e., the ketonization (KR) and esterification (ER) routes, were evaluated for the production of mixed alcohols from brown algae. The alternatives were rigorously simulated using Aspen Plus v.8.6 for 400,000 tons dry brown algae/year. The simulation results were used to develop techno-economic models and to evaluate the alternatives based on their profitability, energy requirements, and greenhouse gas (GHG) emissions. The results showed that the KR is superior, with a net present value (NPV) and present value ratio (PVR) of 61.1 million dollars and 1.57, respectively, over the ER, with a NPV and PVR of − 55.1 million dollars and 0.48, respectively. The total energy costs of the KR and ER were calculated to be 11.6 and 37.2 million dollars/year, respectively, while emitting 109.7 and 307.6 kton CO2 equivalents (CO2-eq)/year GHGs. The economic model was used to perform a sensitivity analysis and calculate a maximum dry seaweed price (MDSP) of 90.0 $/ton for the KR.