what is lignin? Lignopure

Written by: Wienke Reynolds – Co-Founder and CTO at Lignopure


Fossil-based products, especially those derived from petroleum, govern our daily life. Not only for transportation, but especially in the materials and chemicals that surround us: Plastics in packaging and more durable products, fibres, foams, foils, paints and resins, adhesives, solvents, cleaning products and even cosmetic ingredients – the list appears endless! And our consumption is massive. For 2021, BP estimated the annual production of oil products to be 4221.4 million tons, including crude oil, shale oil, oil sands, condensates and natural gas liquids.  

The climate change urgently calls for a change, but fossil products are still too cheap, too convenient and well available, the industrial transformation a significant effort. For 2014, BP published a number of estimated 1.700 billion barrels of crude oil still available in the worldwide reservoirs. This equals approximately 270 billion m³. And despite the still growing demand, we keep finding more oil.  

For the energy and mobility sector, alternative solutions like electromobility or hydrogen are under development. But especially for chemical products, bioresources will need to play a major role. Out of the consumed oil, far less than 10 % are used for chemical products via a finite number of so-called platform chemicals, the rest is being burned. Still, this is an incredible amount, and in order to replace this massive fossil resource with a renewable one, a huge, ideally industrial, bioresource is required.  


Industry is still avoiding the change 

Lignocellulosic biomass as the biggest renewable terrestrial bioresource seems to be our best candidate. Lignin is the second biggest fraction in lignocellulose and as an industrial side stream of the pulp & paper and biorefining industry, it is considered a major pillar of the biotransformation in the European bioeconomy strategy. According to literature, the worldwide production of lignin was approximately 100 million tonnes/year in 2015. Lignin is a phenolic polymer and its huge potential to act as a renewable alternative to many fossil-based materials. Especially its natural protective properties, such as antioxidant or antimicrobial activity, UV-protection, mechanical reinforcement and reactivity are attractive for diverse applications. However, depending on the biomass type, isolation and downstream processing, lignin quality differs significantly between the sources and often even shows strong inhomogeneity within the same source.  

Unfortunately, lignin itself or even lignin-based intermediates will not necessarily form a true drop-in solution for established fossil-based chemicals and materials and new processing routes will need to be implemented. Furthermore, product formulations and manufacturing processes will need to be redesigned in a lignin-specific manner. Consequently, industry is still very hesitant to invest in the development and production of novel lignin-based products, although the consumers demand novel sustainable solutions. Sadly, lignin, this characteristic brown and variable material, is still widely unknown – both by consumers and industry.  

History levers out the most common prejudices against lignin as fossil replacement 

But why do the challenges with lignin sound so familiar? They do, because the beginnings of petroleum use were quite similar. Already 12 000 years ago, the sticky, black-brown viscous liquid was used to seal boats, later also for lighting. From the 9th century on it was even used as medicine in the Islamic countries. The modern use of oil started in the 19th century in the USA when petroleum became a cheap and successful alternative to whale oil, which urgently needed a replacement. Later, people started to refine it and further develop its applications. It even played a decisive role in both the first and second world war. However, the petroleum’s major application was fuel, the first oil-based phenolic plastic Bakelit was only developed in 1907, thousands of years after its first discovery.  

So, will it take us as long to establish lignin as a major resource in our daily lives? We believe not, because we have learned a lot from oil processing, and we already know a lot of lignocellulose refining from the pulp & paper industry. Furthermore, we can transfer many of the principles to enable a much faster and smoother rise of the lignin. Reading more on crude oil composition and use, the similarities are quite striking. If we blame lignin diversity as a major hurdle for its use, why is this not an issue with crude oil any more? On our most well-known online encyclopaedia, an impressive list of 286 different crude oil products can be found, all varying in composition and properties with over 17 000 components. Interestingly, crude oil is even being classified according to density and its sulphur content, just like we would group lignin types into sulphur-containing and sulphur-free ones, ranging between 0.0 and 5.7%. Also, the phenolic content would vary significantly between the different sources. Oil was formed in nature and is a variable as lignin, but the petrochemistry has come up with smart technological solutions for this, specialized plants or simply blending of crude oil to achieve the desired consistent raw material quality. These principles we can transfer to lignin processing as well. The controversial discussion, if the technologies and industry would been developed as fast without crude oil as resource, we shall not address here.  

Fun fact: At Lignopure, we are continuously growing our library of sulphur-free lignins for high value applications. We have roughly the same fair two-digit amount of sulphur-free lignins in our library as crude oils can be found in the list with a sulphur content below 0.075 %. A good quality “sulfur-free” hydrolytic lignin on the other hand could easily contain 5 times as much sulphur naturally.  

Lignin, as major fraction of wood, grasses and other wood-like biomasses, of course has been a part of our lives even longer than oil, and we have benefited from its properties in many ways through our everyday wood-based products. However, lignin (or “le materiel incrustant” as it was originally called), was isolated and recognized as separate fraction only in 1838. After this, first pulping processes were developed and research on lignin intensified. In the 1930s and 1940s early lignin products (lignosulfonates and Kraft lignin) came up with applications in leather tanning, as dispersants, in rubber or ceramic industries, where they are still being used today.  


The change is possible 

Interestingly, the actual necessity for raw materials and crude oil shortage already resulted in viable biorefining concepts producing lignin as a side stream already almost 100 years ago. In the former USSR, dilute-acid hydrolysis plants were in operation using softwood as raw material. The first demo plant was commissioned in 1935 and until 1985, 18 bioethanol, 16 fodder yeast and 15 furfural/xylitol hydrolysis plants were in operation – some of them until 2010s! The lignin was incinerated or landfilled. These landfills are mined today for firing briquettes or pellets, but also for material applications or even food supplements in Russia.  

Higher value applications start to appear from the 1990s, for example with Tecnaro’s lignin-based bioplastic compounds, and have been strongly developing since then! At Lignopure, we especially aim to replace harmful fossil-based chemicals in cosmetic products. This is a rather new field, the first ideas of using lignin as filler in cosmetics appear in research papers in the early 2000s. After 2010, research started to emphasize the UV protection and multifunctionality provided by the lignin, with a real hype from 2015 on with an increasing number of publications. However, this has been almost exclusively research focused and an actual marketing, scale-up and application validation were still missing. This is the challenge we accepted and what we are passionately working on at Lignopure. We see huge potential to not only provide safer and more sustainable ingredients for our daily cosmetic products, but to actually create awareness of lignin as an alternative to fossil resources and to create a demand from the consumer side.  

What makes lignin different from oil is of course the fact that it mostly would be available as a solid, not a liquid. The processing routes starting from the crude material would need to be different from the petroleum-based industry, focussing especially on transforming the lignin into ready-to-use dry powders with a defined and consistent quality that meets the requirements of as many end applications as possible. With our particle technology expertise for lignin transformation, we are actively supporting this goal and act as pioneers in the field of high value lignin applications with our flagship product LignoBase. Other routes, like for example proposed by Vertoro, focus on a depolymerization of the lignin into liquid fractions, just like crude oil constituents would be cracked into shorter chain fractions.

We are eager to walk the extra mile 

So, yes! It can be possible to build a lignocellulose and lignin-based bioeconomy if the demand as well as the necessity and motivation are strong enough. And they should be with the climate actions we have to face! With the experience from managing the naturally also very heterogeneous crude oil or big biobased resources such as cellulose, we do have a strong basis and smart technology solutions at hand to give lignin its rightful place in our daily products. What we need to do is to join our forces amongst all stakeholders and industries and to actually make it happen! 

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