Nowadays, there is a growing need for consumer products such as plastics or resins, which mainly originate from fossil fuels. Plants, including energy crops, agricultural and wood waste are renewable resources with significant potential. Lignin, which is one of the components of plants, is a natural polymer, acting as the glue that gives plants their structural integrity. Currently, it is unfortunately seen as ‘waste’. Yes, this is how the industry sees lignin. ‘You can make anything you want out of lignin except money’ – a slightly ironic, though frequently heard joke in the scientific community. But times are changing. The chemical structure of lignin shows that it has an array of profitable uses and an exciting future!
Can you imagine a bio-sourced brown powder that is not coffee but could still be worth up to $2000 per ton in the future? This idea brings a lot of excitement for plant chemistry scientists. In the last couple of years, lignin has gone through different steps: from a residue that was only useful for energy applications into a sustainable alternative for fossil fuels. It might sound impossible, but you can even use it to make vanilla!
Economic analysis shows that use of lignin for energy applications alone is not economically viable. ‘The economic incentive of bioethanol plants is currently very low, but if we can make value-added products from the largest side stream, that might change’- said researchers from Aarhus University.
Direct use of lignin or its conversion to building blocks for polymer production can create a commercial opportunity in upcoming years. A primary objective is to develop new synthetic materials using natural resources as a starting point which will provide similar or enhanced properties to their petroleum-based counterparts.
Let’s give an example. Synthetic adhesives which are made out of oil and their components, such as formaldehyde, are highly toxic (formaldehyde is clasified as a carcinogen in the US). We want to stop using it, but first we need a good alternative. And lignin fits this gap perfectly. It’s just like a ‘hot’ item.
The main aim of my research was to identify potential technologies for new lignin fractions and make them a truly feasible resource. In order to convert biomass to main components, a pre-treatment process is needed. It breaks apart the plant structure and makes extracting the main components easier. Imagine you are making a spinach smoothie using a blender. Once you press the start button, the leaves break apart and you get a liquid, which is easy to drink.
My innovative method was based on combining a pre-treatment process called steam explosion and an extraction method called organosolv. Steam explosion is a very valuable technology. By using steam, it is more environmentally friendly than other processes. On the other hand, the organosolv process produces relatively pure lignin. It was hoped that the combination of these two processes will influence the chemical properties of lignin, thereby making it a more viable product in terms of suitability for production of plastics or resins. It was not easy to strike a balance and find the lignin which would fit a whole range of good properties, but ‘no gain without pain’- they used to say.
By the look of it, wheat straw lignin obtained from a combined steam-explosion/ organosolv process seemed to have all the needed properties for production of different materials like polyurethanes, phenolic resins and polyesters. It’s only a matter of time before these results can be implemented in practice, but the old joke has already been proven wrong. I predict that in the near future, lignin will become a serious raw material for the chemical industry and a serious source of money.
About the Autor:
Anna Suchy is a biology graduate with an MSc degree, currently based at Aberystwyth University where she is completing her PhD. Her current research activities include converting plants and agricultural waste into biomaterials. She also works on a start-up project Cophenol (converting coffee waste into high-value products) and leads science outreach activities for kids. She is
particularly interested in climate change, sustainability, teaching and public engagement. Apart from science she loves travelling, singing and playing music.