Designing a Lignocellulosic Bioplastic

Abstract

This paper concerns the development of thin films from lignocellulosic biopolymers using deep eutectic solvents (DES). The primary objective is to modify the lignin component and alter material properties, through inclusion of ethylene glycol in a previously proven choline chloride based DES. Additionally, citric acid-based systems are investigated as a greener alternative to more conventional DES chemicals.
This research contributes to the growing field of lignocellulosic biomass as a valuable resource to substitute fossil fuels. The material characterization techniques utilized were scanning electron microscopy, for surface structure analysis; thermogravimetric analysis, for thermal property assessment; contact angle measurements, for hydrophobicity evaluation; and nuclear magnetic resonance for assessing
the recyclability of the DES. Findings from the study indicate that the addition of ethylene glycol significantly influences material properties, likely due to the protection of important linkages in the lignin component, generally resulting in improved lignin distribution and hydrophobicity. However, the findings
also signaled that DES systems containing ethylene glycol were less effective at fractionation of the lignocellulose, compared to the reference DES without ethylene glycol. Finally, the study demonstrated promising recyclability of the DES used in the process, with NMR analysis confirming no detectable impurities. While unsolved challenges regarding the optimization of the film fabrication process to achieve higher mechanical strength remain, the research can conclude that ternary DES systems hold substantial potential. The recyclability of solvents and the, at the moment of writing, abundance of lignocellulosic waste make this method a viable option for future material development, which should focus on optimizing the alternative DES solutions and fabrication parameters.

Popular Abstract

Without question one of the 20th century's most transformative inventions, plastics are cheap, durable and so versatile that it is a challenge to find a product made without them. The unprecedented growth of the plastic industry has coincided with a global shift towards single use plastics and a steady increase in
the global waste generation. The strength of common plastics - their incredible resistance to decay - is also their biggest problem. While only constituting approximately 10% of discarded waste, they don't
decompose. As a result, we see an overrepresentation of accumulated plastic in our natural environment. Completely abstaining from fossil-based plastics is implausible, but it's critical that we strive to replace them with sustainable alternatives with practical end-of-life options like recycling, composting or biodegradation wherever we can. An obvious solution could be the the waste from our farms and forests.

Found in every plant on earth, lignocellulose is a tough and complex material that takes on many different forms based on the properties of its three components - strong cellulose fibres, supporting hemicellulose, and the protective glue that holds it all together, lignin. Today, many production chains
underutilize lignocellulosic resources, primarily agricultural or forest residues, even simply discarding them as waste. As such, the feedstock has huge potential if a simple method of converting it to a usable material is found. One key to unlocking this potential are Deep Eutectic Solvents (DES) a group of non-volatile solvents capable of breaking the bonds between the lignocellulosic components to extract high quality lignin. The term eutectic, from the Greek words eu (well) and teko (to melt), was coined by a British scientist to describe a mixture with a lower melting temperature than its individual parts. The variability of DES systems is practically infinite, and researchers have found that specific combinations will not only dissolve the lignin, but also modify it - making the molecules longer, shorter, or more water-resistant. The low energy consumption and ease of preparation, combined with the abundance of the chemical components make DES promising for sustainable applications even on larger scales.

The process is straightforward in theory. Ground biomass is treated with a DES around the boiling temperature of water for several hours, dissolving the lignin, and breaking the structure of the plant fibres. When water is added to the mixture, the lignin re-solidifies from the DES, creating a regenerated pulp where the cellulose fibres are entangled in a new lignin network. After filtering and drying, we
obtain a solid composite film. The product retains many of its natural properties like biodegradability, while the new internal structure can give it increased strength, flexibility and water resistance. Not only can this process be reproduced using a range of DES systems, but the final material properties, such as rigidity or hydrophobicity, can be tuned based on which DES is utilized. Another benefit of the material is resource efficiency. The primary resource, lignocellulose, is still considered waste in many industries, and the DES and water used in the process might be recyclable.

Despite the advantages, there are many challenges ahead. Reaching the full potential in strength and durability is tricky in practice, requiring careful optimization of the process, for each unique combination of biomass and DES. Large scale production is still far away, requiring more research on the processing and the combination of different types of material pairings. Unlike fossil-based plastics, bio-based alternatives are complicated. But with knowledge and research, complexity doesn't have to bea weakness - it might just be their greatest strength.

• author: Norrman, Hannes
• supervisor: Karen Edler; Maggie Kroon
• organization: Centre for Analysis and Synthesis
• course: KASM15 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: polymer technology, lignocellulose, deep eutectic solvents, film fabrication
• language: English
• id: 9210800
• date added to LUP: 2025-09-25 12:02:18
• date last changed: 2025-09-25 12:02:18