Lignin is the most abundant aromatic biopolymer and the second most abundant polymer on the planet, and it has been estimated that more than 300 billion tons of lignin is present in the Earth with an enormous yearly biosynthesis of ~20 billion tons [1].

Lignin is produced in large quantities as a by-product in the pulping and cellulosic ethanol industries. It is one of the three main components of lignocellulose, with a content of ca. 10-25 % depending on the nature of biomass, with the other two being cellulose (30-50 %) and hemicellulose (15-35%) [2]. Most of this lignin is combusted to generate electricity.

Lignin is effective as an antioxidant and for UV protection due to its radical scavenging ability. It does however posses some disadvantages that can be managed with advanced fractionation and processing techniques.

Economic analysis has proven that it is not economically appealing, especially in the long-term, to use lignin only for energy, compared with applying lignin for high-value chemicals and materials. For instance, when used as energy or as a solid fuel to replace natural gas, lignin is worth only about 150 € per ton [3]. Valorizing lignin into aromatics and polymers, valued over 1000–1200 € per ton, could greatly improve the economics of lignin applications. Lignin's potential market has been estimated to be as large as 242 billion €.

An integral part of the establishment of a bioeconomy in Europe is the development of biobased plastics, i.e., plastics made from renewable sources, as it will contribute towards the gradual independence of our society from finite and non-renewable fossil sources. Lignocellulosic biomass is an abundant source of high added value chemicals. The utilization of lignin is a topic of intense research in the last decade [4], and one of the simplest approaches is its use as a filler in polymer composites [5–8]. Lignin can reduce the cost and increase the biobased nature of polymer composites, while imparting antioxidant, antibacterial and antimicrobial properties. Therefore, it is often blended with polymers such as polyethylene, PE and polypropylene, PP to improve their thermal oxidative resistance.

When directly used for materials, lignin has much lower strength than most synthetic polymers due to its insufficiently high molecular weight, and it has poor compatibility with many synthetic polymers. :arge particle size is a responsible factor against more widespread usage of lignin as filler, since the commercial lignin shows particle sizes ranging from 10 μm to even more than 100 μm. Reducing the size of fillers is known to be beneficial for polymer composites, as larger filler surface areas can impart improved properties to the polymeric matrices. Such particles are too large and may exhibit detrimental impacts on mechanical properties of the resulting composites containing the microfiller at variable contents. The reinforcing effect of lignin for polymer matrix intensively depends on particle size and strong interfacial bonding with the matrix. For this reason, methods to reduce the particle size of lignin have been in the spotlight to make the introduction of lignin as a polymer additive easier and more beneficial [9,10].
Nanolignin can significantly alter the properties of polymers. Small quantities of nanolignin can block UV light, improve thermal and mechanical properties the hydrophobicity and the the crosslinking densities of polyurethanes, all very attractive features for insulating materials. [11] It can also have biomedical applications, as it imparted PVA with antioxidant and antimicrobial behavior with adding only 3 wt% in the composite. [12] Nanolignin can also be used as an initiator for the polymerization of lactides, a concept that is being explored within the BIOMAC project. [13]

The BIOMAC ecosystem has the capacity to cover the whole value chain of lignin, starting from biomass supply all the way to valorization in composite materials. BIOMAC offers the following services to any client operating in the field of nano-structured bio-based materials (NBM), aiming to upgrade existing or develop new concepts within the lignocellulosic value chains of nanomaterials and polymers, starting from Technical Readiness Level (TRL) 4-5.

BIOMAC can fractionate lignin with organosolv-steam explosion and hydrothermal pretreatment of biomass.

BIOMAC can transform lignin to new attractive materials, such as nanolignin.

To increase the added value of lignin, BIOMAC offers innovative transformation processes via its Pilot Lines:

BIOMAC can add lignin products in biobased polymers via reactive extrusion and 3D printing.

Applications of lignin and its products in the BIOMAC project

To learn more about the services offered by BIOMAC and the open call!

References