Aquatic biomass is promising due to its high productivity in less nutrient environment. Gasification is one of the frontier technologies to convert biomass into energy, mainly to produce electricity. Recent development in electrochemical technologies allows the utilization of electricity to upgrade waste CO2 into chemical products. In the present study, the performance of integrated gasification and electrolyzer is evaluated. The gasification converts biomass into syngas and electricity, while the electrolyzer convert CO2 from the gasification residue into chemicals such as CO and methanol by utilizing the electric power from the gasification. The variation of the gasifying agent flow rate (O-2 equivalence ratio between 0.36 and 1.00) provides the variation of syngas composition (H-2: 28-65%; CO: 25-43%) and heating value (12-30 MJ/kg). The production of CO or methanol is significantly influenced by O-2 equivalence ratio and fraction of syngas into power generator. The highest exergy loss is found to be in the cooling system. The net CO2 emission of the proposed configuration is negative (-0.09 to-0.17 kg CO2/GJ at O-2 equivalence ratio of 0.36) by considering the CO2 consumption of the biomass feed. Therefore, this system is promising for further investigation as the future renewable technology for energy conversion. (R) 2020 Elsevier Ltd. All rights reserved.