More answers from the woods – The potential of lignin
Background: Wasted waste
When it comes to sustainability, it is increasingly about the substitution of problematic substances. Many once vaunted “miracles” are becoming more and more known for their negative impacts on the environment. Hence, many sectors are constantly on the lookout for new or alternative materials. But we don’t have to look far! Germany has a high share of an interesting “waste material” which, with 50 million tons annually from the paper industry alone, has a huge potential for users worldwide1. We are talking about lignin!
Lignin [from * lign-], wood pulp, is one of the main constituents of wood and therefore, in terms of quantity, one of the most common natural substances (alongside cellulose) 2. Lignin gives plants shape and stability; the forming of wood in plants is also known as lignification1. The reason why lignin is so incredibly interesting is because of its abundance of aromatic compounds. Lignin is a phenylpropanoid and can be used to make polymers. The resinous substance is the only one with such a high number of aromatic compounds (within renewable resources). These are otherwise obtained from fossil resources and used to produce plastics, paints, fuel and other chemicals. Replacing these limited and environmentally harmful ingredients is desirable on many levels. Especially when, as with lignin, cultivation is CO2 neutral and the manufacture of long-lasting products can even be viewed as a carbon sink.
Lignin is mainly obtained from paper production, although it is currently seen mainly as a waste product. 98% of it are burned. A waste for such an interesting renewable raw material. The substance can also be obtained directly from wood. Lignocellulose is first divided into cellulose, hemicelluloses and lignin. The processing of lignin in the conventional way is currently still too energy-intensive (requires 500°C and 200bar3) and waste-intensive. But more research is being done and new, more economical ways are being invented.
Innovation: The vastness of lignin based products
The innovative potential of lignin seems to be growing steadily and is not limited to one area of application. Here we introduce you to various innovations based on lignin that have sparked our interest.
Due to the high carbon and aromatic content, lignin can be used in a variety of ways. It has already been utilized into various forms of plastics and could replace many plastic products as the price improves (with economy of scale). A lot of items can be produced with lignin-based bioplastic: from office items, to cases of electrical products, kitchen products, to baby toys and many more. The fabric is durable, heat-resistant and very hard-wearing, which makes it an ingenious alternative to fossil resources! In addition, lignin is 100% biodegradable.
Other sectors are also experimenting with the substance. Conventional batteries are based on metal compounds such as lithium, lead and vanadium4. It is well known that the extraction of these precious metals is associated with considerable environmental problems. Recycling the materials is also laborious and rather uneconomical. But anyone who thinks that sustainability and batteries are in opposition to each other could be surprised. CMBlu Energy AG has shown that so-called “eco batteries” are possible. The electrolytes for redox flow batteries, which contain the metals mentioned above, can be replaced by a sustainable, non-flammable and non-explosive alternative. Lignin can be used as a starting material for the production of plant-based electrolytes and thus be a renewable and inexpensive option for new types of batteries5. CMBlu and its partners have already demonstrated the feasibility of electrolytes based on lignin and are now working on improving the economic and environmental friendliness.
Another lignin-based innovation deals with the production of carbon fibers. Companies and research institutions from all over Europe are working on this future-oriented task. The aim is to replace the petroleum-based raw material, the plastic polyacrylonitrile (PAN), which is conventionally used for carbon fiber production6. For a renewable raw material, lignin has a high carbon content. This way, high-quality fiber material can be developed on basis of plant material and fossil alternatives can be replaced.
Lignin can also be used in the field of building materials. It is already known in the construction sector as a binder that does not require formaldehyde. Aerogel (see here: what is aerogel?) Based on lignin could be particularly interesting7. A highly porous panel with excellent insulation properties was, which surpasses conventional insulation materials. This is thanks to the aerogels in the panel. These are normally based on silicon and are complex to manufacture and associated with increased costs. Researchers are now working on a lignin aerogel (so far with 78% lignin)7, which should be far better off in terms of the environmental balance to the previous ones. To what extent the product can be introduced economically is still unclear, but with the constant growth in wood construction and constant production of paper, lignin offers constant accessibility and high potential.
Potential: Lignin and miscanthus
The incredible variability in the use and processing of lignin shows the high innovation potential in a wide variety of areas. As one of the most common natural substances and so far, unused waste product, availability is secure and sustainable. Additionally, we see particular potential in obtaining lignin from miscanthus. Miscanthus is a type of reed, rich in lignin, that also grows on polluted and difficult to manage soils, repairing them and bringing high yields for farmers. With its partner company IVT, BE Solutions has been researching a new type of insulation panel for the last 3 years and now sees the potential in the combination with aerogel. You can look forward to an update and results of this project soon. In summary, lignin has the potential to replace many fossil substances and to shape a climate-neutral future based on renewable raw materials!
References
1 https://www.biooekonomie-bw.de/fachbeitrag/dossier/lignin-ein-rohstoff-mit-viel-potenzial
2 https://www.spektrum.de/lexikon/biologie/lignin/39320
5 https://energyload.eu/stromspeicher/forschung/akkus-elektrolyt-lignin/
6 https://www.maschinenmarkt.vogel.de/lignin-als-rohstoffquelle-fuer-bio-carbonfasern-a-
