Biomass can play a role in mitigating greenhouse gas emissions by substituting conventional materials and supplying biomass based fuels. Main reason for the low share of biomass applications in Europe is their often-high production costs, among others due to the relatively low availability of agricultural land. Therefore, in the short to medium term more efficient and cost effective routes for the introduction of biomass are needed, e.g. the further development of multi-functional biomass systems including 'multi-product use' and 'cascading'. Multi-product use is defined as using biomass for different applications, while cascading is the subsequent use of biomass for a number of applications, i.e. materials, recycling of materials and energy recovery. In this thesis, the performance of multi-functional biomass systems with regard to GHG emissions, non-renewable energy consumption, agricultural land use and costs is quantified. This analysis is carried out by several case studies. For this purpose, methodologies are adapted for the evaluation of multi-functional biomass systems. For example, issues of allocation, accounting for time and market price changes due to the introduction of biomass have been considered. Most multi-functional biomass systems regarded in this thesis increase the potential benefits of biomass use in terms of costs, GHG emission reductions and agricultural land use. In comparison to single bioenergy systems, multi-product systems investigated decrease primary biomass fuel costs by about 5 to more than 50 €/GJLHV. Cascading chains of short rotation wood that are analysed alter the GHG emissions avoided by about –13 to 23 Mg CO2 /(ha*yr) and modify the costs by about –300 to 2000 €/Mg CO2. Finally, multi-functional biomass use in a PLA bio-refinery system leads to additional benefits of about 4-12 Mg CO2eq /(ha*yr) and 0-200 €/Mg biomass input. The type of materials and energy carriers that are substituted and the waste management system have proven to be crucial for costs as well as for GHG emission reductions obtained for biomass systems. In the case of bio-materials that have a relatively long lifetime, time dimensions can play an important role. Market prices of land, materials and energy carriers influence the economic performance of multi-functional biomass systems strongly. Research indicates that with a growing use of biomass for materials and energy, GHG emission mitigation costs of these options may increase. This is especially the case for bio-materials that have comparably small markets. In conclusion, to use biomass efficiently in terms of GHG emission reduction, (agricultural) land use and total costs of the system, multi-functional biomass systems can be an attractive option if carefully designed, depending on reference systems and land, material and energy markets. The best multi-functional biomass systems analysed in this thesis increase the GHG emission reduction per unit of agricultural land used by a factor 5 compared to single biomass uses and decrease the total systems costs by about the same factor. However, for the performance of biomass systems at a large scale of biomass use, the interactions of biomass use with land, material and energy markets need to be better understood.