Co-firing of solid biomass in existing large scale coal power plants has been supported in many countries as a short-term means to decrease CO2 emissions and rapidly increase renewable energy shares. However, many countries face challenges guaranteeing sufficient amounts of biomass through reliable domestic biomass supply chains and resort to international supply chains. Within this frame, novel pre-treatment technologies, particularly pelletization and torrefaction, emerged in recent years to facilitate logistics by improving the durability and the energy density of solid biomass. This paper aims to evaluate these pre-treatment technologies from a techno-economic and environmental point of view for two reference coal power plants located in Great Britain and in Italy. Logistics costs and carbon emissions are modelled for both international and domestic biomass supply chains. The impact of pre-treatment technologies on carbon emission avoidance costs is evaluated. It is demonstrated that, for both cases, pre-treatment technologies are hardly viable for domestic supply. However, pre-treatment technologies are found to render most international bioenergy supply chains competitive with domestic ones, especially if sourcing areas are located in low labour cost countries. In many cases, pre-treatment technologies are found to guarantee similar CO2 equivalent emissions performance for international compared to domestic supply chains