Hydrogen is an energy carrier that represents a possible clean fuel of the future. This paper assesses the effect of biomass co-firing on gasification based hydrogen production supply chain, with carbon dioxide capture and storage, from technical, economical and environmental point of view. Several cases consisting of various feedstocks to the gasification reactor are investigated (coal only and coal in mixture with sawdust or wheat straw). Considered plant concepts generate between 330 and 460 MW hydrogen of 99.99% (vol.) purity. First a performance analysis regarding the energy efficiency of the process, the syngas composition and the carbon dioxide capture rate is carried out. The simulations are made using chemical process simulation software Aspen Plus. Second, total capital investment and operating costs for the gasification plant are evaluated. Finally, using the results from Aspen Plus simulations and the cost estimations, a discrete event model is developed, to address hydrogen production supply chain analysis under demand variability, with Arena software. The implications of biomass co-firing on the system are evaluated in terms of: hydrogen amount sold and hydrogen amount stored (MW), hydrogen lost sales amount (MW), partial sales percent and gasification plant profit. The results show that as the biomass quantity in the feedstock increases the hydrogen production rate decreases by 9-28% for sawdust, respectively by 7-23% for wheat straw. The energy efficiency of the process and the gasification plant profit also decrease, but the CO2 emissions are lower for the cases of biomass co-firing. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.