The global consensus of carbon neutralization calls for new ideas of CO2 capture, conversion and utilization, especially CO2-negative technologies. In this work, a CO2-negative process was developed to convert three different types of biomass species into valuable products, green hydrogen and activated carbon (AC). Four reaction modules including pyrolysis, activation, gasification, and chemical looping were integrated and balanced in terms of mass and energy. After optimization, green H2 with up to 95.54% purity can be produced with price as low as $3.10/kg. The solid AC product can fix 10-20 wt% of carbon element from biomass to achieve a similar proportion of reduced CO2 emission. Part of the separated CO2 can be reused in the activation process and converted to CO product for internal use. Overall, this process demonstrates an economic route for biomass conversion with the co-production of green hydrogen and value-added AC products. Moreover, CO2-negative emission is also realized.