A large quantity of plant wastes (such as wood scrap, rice bran, used tea leaves, and the dregs from squeezed fruit) is generated by the woodworking and food industries and agriculture. The recycling of these wastes is limited to their use in feed, fertilizer, fuel, and cosmetics. In this study, by using lignin that is one of the main components in plants, a new recycling method for plant wastes was designed. Lignin is a phenolic high-molecular-mass biopolymer based on phenylpropanoid units that are unique to vascular land plants.

Outdoor exposure tests of wood plastic composites (WPCs) were conducted at seven sites in Japan. The tests examined the process of chalking on the surface of the WPCs and the weather factors affecting chalking. Observations using a scanning electron microscope and a polarization optical microscope (POM), analyses of Fourier transform infrared spectroscopy, as well as differential scanning calorimetry showed that the deterioration of both wood and polyolefin elements occurs on the surface of WPCs. The POM observations revealed that surface sanding of WPCs in the manufacturing process promoted more chalking. Furthermore, it became clear that among the weather conditions studied, temperature and global solar radiation had the greatest influence on chalking, as determined from the results of single regression analysis.

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