The resource principle. Utilization and intelligent reprocessing routes for wood-based materials, natural fibers and organic residues

From time immemorial wood has been used for a very wide range of applications on account of its mechanical properties. Its uses range from static applications in the construction industry and interior design, where for the most part load‐bearing structures are maintained, and extend all the way to energetic use - in other words, its complete degradation to water, minerals and carbon dioxide. There are numerous intermediate levels of physical and/or chemical treatment between these extremes. In Sects. 14.2 to 14.5, applications are described where all statically significant structures are retained and combined with other materials such as glass fiber or even concrete to optimize mechanical properties. Here, chemical processing is limited to the bonding of wood components with each other or with other materials. These diverse combinations allow new mechanical properties to be achieved. If a hierarchical structure that results in an anisotropic distribution of mechanical properties is broken down, a near‐isotropic distribution profile, with respect to mechanical properties, can be achieved in composite materials. If the focus is on the chemical components rather than the mechanical structure, then wood can be broken down and fractionated using a variety of methods. Nine of these processes are described and evaluated according to their respective technical maturity. To this end, it should be noted that there are different stages of development: from an established need for pure research through to industrial applications that have already been implemented. A distinction should be made between those processes which preserve the chemical structures - where lignin, hemicellulose and cellulose are regarded as fundamental structures worthy of preservation - to those which break down these structures. While many mature applications already exist for cellulose and hemicellulose, lignin, apart from a few applications, still requires a great deal of research in order for the synthetic efficiency of nature to be optimally exploited. When methods are used that degrade the above‐mentioned target structures further, the end products are small molecules, which can be introduced into the gas network to store energy as fuel (bioethanol) or as methane, or can serve as raw materials for other processes of the chemical industry. An essential criterion for all these processes is that no residues remain, but rather that residues from other processes can even be included in the cycle. It is of interest to the chemical industry that components can be discharged at the different stages of digestion, which can in turn be used for further production and replace fossil resources. Should further use no longer be meaningful after various product cycles, then thermal utilization is still possible and the resulting carbon dioxide can be reintroduced into the resource cycle by using catalysts and energy.