This paper presents t-OPTIMASS, a multi-period mixed integer linear programming model to optimise strategic and tactical decisions in all kinds of biomass supply chains taking into account the geographical fragmentation and temporal availability of biomass and changing biomass characteristics due to handling operations. Unlike existing models, t-OPTIMASS considers the growth and regeneration of biomass to determine the optimal harvesting moment(s). t-OPTIMASS is demonstrated based on the use of grass from nature reserves and road verges to substitute maize in the digestion mixture converted in the currently available wet anaerobic digestets or potential dry anaerobic digesters in Limburg (Belgium). The results highlight that the decision process is driven by the requirements imposed to the characteristics of the biomass to be converted at the conversion facility. The harvesting moment is defined and pre-treatment operations are introduced to make sure that biomass is delivered with characteristics that fit best these requirements. The analyses indicate that storage facilities are indispensable to deal with the temporal availability of biomass, the conflicting temporal demand and the required constant feeding of the digesters. t-OPTIMASS allows users, interested in macroanalysis, to define biomass potentials, to support policy decisions, to evaluate the feasibility of new facilities, etc. (C) 2015 Elsevier Ltd. All rights reserved.