Biobased polymer composites (BPC) become increasingly significant in the light of climate change and depleting fossil resources. Consciousness of these global environmental problems has underlined the importance of the development of biobased composites, which is now promoted by global and EU level initiatives like EU Bioeconomy Strategy and OECDs “The Bioeconomy to 2030” project. One of the most challenging issues in the development of natural sources derived composites is increment of biobased content by keeping possibly high functionality of the multi-phase system. Since decades wood flour (WF) is broadly used as technically comparatively effective and economically viable reinforcement [1]. The effectiveness of WF, however, is limited to some extent due to comparatively low aspect ratio of the reinforcement. Flax, hemp, jute, ramie, kenaf, sisal, harakeke and many other natural fibers [2] with considerably higher aspect ratios have been used as an alternative to WF to increase reinforcing efficiency of BPCs. In later years increasing attention is devoted also to the fibers derived from other forms of lignocellulose sources, including agricultural waste [3].