Green biorefinery (GBR) is an alternative use of grassland biomass. GBR involves applying technology to chemically and physically fractionate (split) biomass such as grass and grass silage to produce marketable products. Three GBR system models were developed in a companion paper to determine, using scenario analysis, the most technically feasible scenario for the development of a blueprint Irish GBR system. The three GBR system models were a combination of feedstock system and biorefinery technology: Grass/silage - basic technology (GS), Silage - basic technology (S) and Silage - advanced technology (AT). The models were then assessed at different input volumes. The focus of this paper is on the development of the economic modelling component of the three GBR system models in order to identify which of the previously selected GBR scenarios is the most technically and economically viable to develop a blueprint for a first generation GBR. Six scenarios were assessed in this paper. The GS, S and AT GBR systems, at two input volume rates: medium volume and low volume. Additional scenario analyses were also carried out to investigate two possible production scenarios "No Prot" (fibre product only), and "Prot" (includes proteinaceous secondary product). Both the economic and technical scenario analyses of this paper and its companion paper suggest the most appropriate GBR systems for a first generation Irish blueprint are the combination of Silage feedstock basic biorefinery technology (S), at the medium input volume and both "Prot" and "No Prot" systems. (C) 2011 Elsevier Ltd. All rights reserved.