Biomass gasification represents an effective and promising conversion technology to different energy carriers/chemicals. Biomass gasification with CO2 capture will give an energy conversion system with negative CO2 emissions. This work assesses the techno-economic and environmental implications of decarbonized green hydrogen generation using the biomass gasification. Several pre-combustion decarbonization technologies were evaluated: chemical and physical scrubbing (absorption), membrane, hybrid membrane - chemical scrubbing. All evaluated biomass gasification concepts have 300 MW hydrogen output (corresponding to 100,000 Nm3/h hydrogen with purity above 99.95% vol.) with 90% carbon capture rate. Different system engineering tools were employed for the integrated assessment. As an important novelty outcome of this work, the green hydrogen production from decarbonized biomass gasification has promising potential to deliver high energy conversion efficiency (in the range of 57–59%), lower energy and cost penalties for decarbonization (about 2.2–3.5 net points), negative carbon emissions (considering that the primary fuel - biomass - is of renewable source). Among various assessed decarbonization technologies, the membrane system shows better techno-economic performances than the gas-liquid absorption (e.g., reduced CAPEX and OPEX by 7% and 7–9% respectively, inferior hydrogen production cost by about 7% etc.).