In recent decades, the necessity to find a completely environmentally friendly substitute for synthetic fibres in composite applications has intensified, driven by the objective of reducing emissions in both the production and disposal of composite components. Natural fibres present a potential solution, yet they have some issues such as the inhomogeneous quality of their cross-section and mechanical properties, depending on different aspects, for example, growing conditions and the amount of intake water. Another potential solution is organic man-made fibres, such as fibre made from Cellulose NanoFibrils, which do not present the previously cited drawbacks. This thesis investigates and compares the potentials of organic fibres, either man-made or natural, in composite reinforcement applications.