Present Scenario and Future Scope of the Use of Wood Waste in Wood Plastic Composites

Wood plastic composites (WPC), a class of biocomposites, represent important tools in the production history of sustainable materials and substantial breakthroughs in the area have been realized to enhance their physical and mechanical properties (Das et al. in Sci Total Environ 512–513:326–336, 2015a). However, disadvantages still exist, such as lower mechanical resistance and consequent necessity to increase part size, inferior dimensional stability, higher density, discoloration, flammability, and rottenness. These factors limit the adequate application of biocomposites in wider markets, and although studies have been conducted to alleviate these drawbacks, further investigation is necessary to solve these problems and relieve as many deficiencies as possible (Nagarajan et al. in ACS Omega 1:636–647, 2016). Current literature on the theme shows that these WPCs can be fabricated from a wide variety of polymer matrices, including LDPE, HDPE, PP, ABS, PVC, and PLA. However, there are disadvantages which limit the applicability of WPCs: processing temperature is limited by wood degradation at high temperatures; the incompatibility between hydrophobic matrices and hydrophilic wood fibres; reduction of mechanical properties if compared to parent materials; and finally, flammability issues derived from the flammable nature of wood. Two routes stand out to overcome these difficulties: the use of additives or other reinforcements in association with wood particulates, and the transformation of the wood particles itself before addition via physical and/or chemical processing. From the environmental point of view, the pyrolysis process emerges as a possible solution to recycle several types of residues (including wood) into a higher value material known as biochar. Considering the recent publication trends, it seems that biochar production may be the future target for wood residues since biochar can be used for a myriad of applications, including reinforcement of a new generation of biocomposites, called second generation WPCs. Other advantages are the reduction of carbon footprint and the use of low-cost raw materials. This class of products may be called WPBC—Wood Plastic Biochar Composite. Given the significant number of production variables, this material must be better studied and tested in composites of biological basis.