Brown is the new green: Lignin in plastic
Lately I’ve been learning about plastics and recycling. Today, I stumbled on something new: lignin. It’s the brown stuff inside trees that usually gets burned as waste in the paper industry. But now, a company in Sweden, Lignin Industries AB, is turning it into bioplastics.
Lignin is basically the natural glue in plants. It makes wood rigid and brown. In paper production, it’s the part they remove to make white pulp, and normally it just gets burned as waste. Old book papers and newspaper are yellowing with age just because lignin left inside of paper. So, less lignin means more quality in paper production.
But today we are going to learn that with some basic chemical tricks, lignin can be used as a carbon negative additive to plastics.
Bad news is, it is something slightly more expensive and uglier than shiny white plastics.
Let’s get into details.
Scottish forestry family in Sweden
Dr. Christopher Carrick, founder of a Lignin Industries AB, is actually the fifth generation of a big forest industry family. I mostly learned what I learned about lignin from his voice and company website.
Interesting that they actually came from Scotland a while ago. Just because they ran out of trees in Scotland :) And they introduced football in Sweden.
Natural carbon capture: Photosynthesis
His argument is if nature already has a very solid carbon capture mechanism, why not use it as much as we can.
Beautification of Forest Industry
People often think chopping down trees is automatically bad, but forestry has actually been one of the oldest and most sustainable ways humans have produced materials. It takes about 50 years for a tree to grow back. Compare that to fossil fuels — their “life cycle” is 400 million years.
Yet we rarely see oil being pumped, so it doesn’t trigger us. But when someone cuts a tree, it’s visible, and people get angry. A lot of it is cultural, not ecological.
Praise for plastic
Dr. Christopher Carrick and I think in the same way here. Plastic is, without any doubt, great technology. We owe a big thank you to plastic, If we are happy about all technological advancement. But nowadays, every culture started to realize plastic waste is a growing big problem.
I don’t think the carbon footprint of the plastic is actually a big problem. If you compare it to not use it, fine. But If you need to use package or whatever you need, whatever material you choose probably has way worse environmental impact to the world.
The real cultural shift we need is use less. But today, we are going to say, let’s put some carbon negative lignin to plastic powder to make it more environmental friendly.
Lignin powder: Renol®
Direct quote from Christopher:
We buy it as a powder, we inject that, or we feed that into a plastic extruder. It’s called lignin, two warm screws that heat up the material. And then we combine that with a natural oil, something that grows as well, because that lignin molecule as such is not so useful. So we upgrade it by, by attaching natural oil onto that structure.
what happens is that that material becomes obviously more oily. And the more oily transformation makes it soluble in other plastics. So we use this material as a drop in material to partially replace the fossil counterpart.
They convert lignin by combining it with a bio-based oil, producing thermoplastic granules called Renol®. They say lignin isn’t just sustainable — it’s scalable. Over 700 million tons of lignin are produced globally every year.1 But what does that mean, really? For context, global plastic production today is over 460 million tons per year (and rising).2 It was just 2 million tones in the 1950s.3
Since lignin is carbon negative due to the photosynthesis, because it’s absorbing atmospheric carbon dioxide when forming biomass, it surely reduces carbon footprint of plastic. It is also recyclable by design by remaining stable through multiple cycles.
But it makes plastic less functional, a bit brown and more expensive. Less functional means it can’t be used everywhere, but thankfully plastics have plenty of applications where that’s fine.
So, reducing average carbon footprint without reducing total consumption is a bit hard to understand. Sure, it’s economics of scale — any reduction in carbon footprint is good. But history tells us: when you make something easier and cheaper to produce, consumption usually skyrockets. Maybe what we really need are taxes that make plastic more expensive, not cheaper. Anyway, at least this time we have slightly more expensive solution :)
Usage areas
Consumer electronics
They are trying to work with consumer electronics. They are making some speakers, computer items, headphones. But it is new material, it is brown instead of beauty of white. It has increased price and uncertainty of product functionality. When blended with polypropylene:
Renol achieve up to 98 % CO2 reduction compared to virgin PP by combining Renol® masterbatch with recycled PP
Enables full recyclability with the lignin component bringing high amounts of antioxidants to the mix
Its natural color is a brown, reminiscent of the trees from which it is derived
Possibility to colour in to other colours, except white and transparent colours
Strong forest and circular narrative4
Pallets
They are also producing pallets for industrial applications. There, you can tolerate ugly plastic, but it supposes to be cheap and functional there as well.
Renol® virgin ABS 5050 (a masterbatch with 50% Renol® and 50% virgin ABS) is our first lignin-based ABS masterbatch resulting in a 20% CO2 reduction in injection molded products compared to virgin ABS.
E-commerce bags
E-commerce bags based on recycled plastics and lignin. Both reducing fossil use and lowering carbon emissions. Even compared to paper bags, lignin e-com bag has lower GHG emissions, comparable energy use and reduced storage needs.6
Waste bags
Waste bags, garbage bags and those kinds of stuff. Can be easily ugly, even preferred to be ugly. He said, they can produce as much as customer wants.
Design Items
And design items. That might be the easiest market to penetrate. Being proud of using tree based plastic.
What so
So, another attempt to use residual material from other industry to make plastic more environmental friendly. Probably, there are a lot more important things in plastic production. But, today we learned together that we can basically add some paper to plastic powder.
Sources
Bruna Pinhoni
Further Reading
https://www.sciencedirect.com/science/article/pii/S2589004224006394
Sarah Millard
