New Chemistry for Renewable Raw Materials
Tetsuo Kondo, Kyushu University
What is the goal of “New Chemistry for Renewable Raw Materials” ?
It is no doubt that it will provide novel green processes for utilization of renewable biomass as an eco-friendly, low-energy, low-cost material-producing method to establish the future sustainable society.
Then, what is “New Chemistry for Renewable Raw Materials”?
The answer is diverse. Prior to the details, we have to define the renewable raw materials, namely bio-based materials. When the large amounts of them exist, we call it “biomass”. Bio-based materials are categorized into two aspects, which are for biological functions, as well as material-functions for human usages. Biological functions of renewable raw materials are more fundamental, and thereby basic researches are required.
Nature always creates patterns including shapes, colors and movements, which strongly connect with various functions in lives. To study them is for understanding not only creation of nature itself, but the pattern-property relationship that can also inspire and guide a novel fabrication of bio-based materials. Here, the double helix of DNA is the most typical and minimum pattering of all bio-based materials. Therefore, attempts to understand the pattern are one of the hottest topics in scientific fields, and further based on the understanding, a design for fabrication of unique materials would be of great importance to utilize renewable raw materials as an alternative resource for fossil fuels. So-called “bio-refinery” concept is included in the above.
Bio-based raw materials are built up from self-assembly of molecules till a higher leveled structure. The key process for each step is formation of the interactions at the individual sizes. The obtained structure is called as “Hierarchical structure”, which is fabricated by the unique architecture of nature. Thus, it is important to realize the 3D hierarchical formation. This understanding is also applied to the top down or down sized process of biomass from the large sizes into small scales including nano-levels. Our technique in Kyushu University1, the nano-pulverization by “Aqueous counter collision”, successfully decomposes only the interaction, and finally liberates the components including bio-nanofibers at various sizes into water to provide a transparent and homogeneous component/water system. Another down-sized method is using supercritical water to perform saccharification of lignocellulosic biomass as a source of bioethanol.
Again, what is “New Chemistry for Renewable Raw Materials”?
We have to re-consider it from the view point of advantages using renewable raw materials. The present advantages are i) conversion into bio-energy by fermentation and ii) conversion into bio-based functional materials including biomass plastics and fiber-reinforced composites. As an alternative of fossil fuel, biomass energy conversion has attracted much attention. However, much less attention for the biomass conversion into bio-based functional materials is paid at present. The bottleneck is a relatively high energy cost, slow process and a complicated processing for final products. The “aqueous counter collision” method and supercritical water above mentioned are listed to rationalize the disadvantages. It should be noted that international sharing of new technologies is negotiable among the countries.
We, of course, should not forget drastic increasing amounts of CO2 in recent years. Therefore, C1 chemistry from CO2 to bio-based functional materials attracts much attention, which required new catalysts to modify CO2. The details will be discussed by Prof. Nozaki, our speaker.
Concerning fabrication of the specified functionalized materials, extensive efforts are inspired by nature, though they are not necessarily composed of bio-based materials. As described above, understanding structural pattern-property relationship in the natural products is an initiation. For example, the Lotus effect due to the rough surfaces of the leaves exhibits hydrophobicity and a strong adhesion of geckoes is in fact due to the micro/nano hierarchical hairs. Then, they will be modified to fabricate artificial ones.
In this way, we should develop superior bio-based materials with 3-D novel nano/micro hierarchical structures. It is noted that those proposed methods should be environmentally friendly, compared with conventional methods in terms of both energy efficiency and cost performance.
1. Kondo, T. et al., US patent No.7,357,339.
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