The need for producing renewable fuels from biomass has increased due to depleting fossil resources and environmental concerns. However, the low fraction of biomass carbon converted to product is an undeniable drawback for most current biofuel productions from fermentation due to undecomposed lignin in biomass composition and carbon loss as CO 2 . In this work, two main production routes of the MixAlco® process, the Ketonization route (KR) and Esteri cation route (ER) are evaluated for the mixed alcohol production by brown algae, third-generation biomass without lignin. A Novel Fermentation process using syntrophic bacteria consortia (SBC) is developed to produce acetic acid from waste gas produced by KR and ER process. The paper investigates the integrated owsheet for these alternative routes, using techno-economic and life cycle analysis to compare the minimum selling price and environmental impacts. The ER's capital and operating cost combined with the SBC is the highest compared with other routes. The cost of raw materials and utilities are the two major cost factors for all the processing routes examined. ER process performs the best in terms of environmental impacts except in water depletion compared with other processes, while the KR process performs the worst regarding the environmental metrics.