The purpose of the current work is the investigation of the Cynara Cardunculus (cardoon) / lignite co-firing concept at the 330 MWe Unit I of Meliti Power Plant, owned and operated by Public Power Corporation (PPC) in Western Macedonia. Meliti Power Plant is involved in the National Cooperation 2011 program, which focuses on the demonstration of large scale biomass co-firing with viable supply chain integration. Results indicate that, although cardoon has relative high percentages of chlorine content and low ash melting temperatures, co-firing has no major impact in the operational and environmental performance of the plant for such thermal shares, while variations in lignite quality account for most of the observed changes. Overall, co-firing biomass in Greek lignite-fired power plants appears to be a technologically promising alternative for GHG emissions reduction. The model takes into account the^non-spherical form of the biomass particle, which influences the drag coefficient and its devolatilization and combustion mechanisms. Simulations under different co-firing ratios and biomass particle sizes are performed for the 330 MWe pulverized-fuel, tangentially fired boiler located in Northern Greece. Validation of the simulations is performed using plant data for the reference case of lignite combustion. The numerical results obtained, which include temperature and species fields, particle tracks and burnout per burner level and NOx calculations, provide useful conclusions regarding the maximum allowable biomass particle size for an efficient boiler operation with a parameter the injection port (primary and/or over fire burners). Additionally, the optimum position for dedicated biomass burners is suggested.