This thesis explores the structural implications of utilising natural fibre-reinforced polymer composites (NFRCs) in wind turbine blades through a numerical investigation. To perform the research, the DTU 12.6 m research wind turbine blade is taken as case study. A sensitivity study is performed, investigating the impact of different material engineering constants on the blade's performance. A structural redesign of the DTU 12.6m blade with NFRCs followed to further investigate the implications of utilising bio-based materials. The findings reveal that the reduced mechanical properties of NFRCs restrict the direct replacement of traditional glass fibre composites. The structural redesign process showed that the torsional rigidity and material strengths are the primary drivers for the bio-based blade design. This differs from the conventional blade design where the tip deflection and therefore specific stiffnesses are the main drivers. In order to meet the design requirements the structural blade design will need to be rethought.