Biomass as a renewable energy source with neutral carbon impact offers a good potential solution for reducing greenhouse gas emissions in conventional coal fired power plants. Therefore, the current paper presents and assesses a conceptual design for large scale sawdust and coal direct co-firing electricity production under oxy-fuel combustion conditions with CO2 capture and storage (CCS) using feedstocks with different coal and sawdust content. The influence of sawdust co-firing on several key technical performance indicators (energy efficiency, auxiliary power consumption, specific CO2 emissions, etc.) was evaluated under the following oxy-fuel atmospheres: 21.8% O2, 28.4% O2 and 35% O2 concentration. The impact of the air separation unit on process performance was tested for oxygen purities of 95% and 99%. It was found that under constant CO2 capture (CC) rate (93%), residual O2 concentration (8%) and gross electrical output (1000 MWe), power plant performances are continuously decreasing with the increase of sawdust feedstock content and supplied oxygen purity. The results also indicate that the increase of O2 concentration in the oxy-fuel atmosphere from 21.8% O2 to 28.4% O2 has a positive impact on process performance while the further increase to 35% O2 leads to lower energy efficiencies.