Let’s talk about it: Unconventional plastic waste solutions
25. 9. 2019 | Source: BusinessInfo.cz
Thanks to one of our most used materials, today often gets nicknamed the “plastic age.” We use plastics in numerous applications, from the food industry and healthcare to construction and automotive. Imagining modern life without plastics is a nearly impossible.
"Let´s talk about it" is a project of Unipetrol company. It´s aim is to explain various sustainable solutions, including all their benefits and drawbacks.
But seeing the growing amount of plastic waste in nature makes many wish we could just ban this material altogether. But could there be a better solution? This time on “Let’s talk about it”, Michael Londesborough invites Alexander Goldberg from Tel-Aviv University to discuss a new way and an unexpected source.
Alex, tell me something about bioplastics and the unique way that you make them.
Bioplastics are a mixture of polymers. Today, most are derived from synthetic sources. There are families of different bioplastics with different properties. The idea is that all of them should come from renewable sources such as biomass. Our focus is on how to best source the biomass to create these polymers to avoid using arable land and drinking water for production. We came up with using seaweed as raw material for the biomass. It did take us a bit of time to identify organisms which are able to eat that seaweed, but we found the right type of polymers in the form of polydydroxyalkanoates, or PHAs.
So one of the largest benefits is that we don’t sacrifice any land or water that we can instead use for food production.
That’s correct. This debate has been going on ever since biofuels first began to penetrate the market. Biofuels also began with the idea of using biomass instead of petroleum for fuel production. Once we began getting into high scale production, we saw an immediate rise in food prices, leading to food riots. This provoked a global debate about how best to produce biofuels. Should we use land that’s currently being used for food production to produce fuel instead? Bioplastics prompt us to ask the same question. Are we willing to sacrifice land to produce polymer materials?
Ultimately, it’ll come down to cost- using whatever is cheapest. How does using seaweed stack up?
Cost isn’t only about what is cheapest, but also what is the most sustainable. The Earth will end up paying for everything. I think that today already, seaweed can compete with other biological sources.
Tell me a bit more about the microorganisms involved in the conversion of this biomass into a biopolymer.
Our initial idea was to use bacteria. That has changed and today we are using a specific type of microorganism called archaea. Archaea are structurally different from regular bacteria and are halophytic, meaning they are able to live in extremely salty environments, such as the Dead Sea. The archea that we use are able to live in environments that go up to 170 grams of salt per liter. They are also able to eat many types of food, not only salt and sugar, but also polymers, copolymers, oligo-sugars, lipids and so on. Eating all of these encourages their growth and PHA production at the same time. We can achieve up to 60-70 percent of their biomass as the PHA.
As a single polymer?
PHAs are a mixture. They are polyhydroxyalkanoates, a mixture of polymers. The major ones we produce are PHB, polyhydrobuterates, but it’s always a mixture of things coming together.
How energy-intensive is the separation of this mixture of polymers from the rest?
Today it’s a rather complicated task. We are working with micro-sized organisms which we need to separate from water or another medium they grow in. We also need to separate PHAs from the inside, so it’s actually quite a challenge. We are exploring numerous techniques to determine the best way to achieve this.
Are the produced polymers thermoplastic? Can we heat them up, melt them down and form other types of materials out of them?
The materials we are talking about are polyesters. Properties ultimately depend on their chain length and exact composition. Today, PHAs are thought to be thermostable plastic composites, meaning that over time we will need to extract them, purify them, separate them by size and then make composite materials out of them. They provide both mechanical and thermal stability.
What do we understand about the decomposition mechanics of the bioplastics you produce and their impact on the environment?
PHAs are interesting materials we harvest from marine organisms. We already have some indication that in a marine environment, they could decompose more rapidly than other materials. From literature, we know that in a marine environment, about ten to twelve percent of these polymers decompose within 400 days. This is a very good rate in comparison with other material decomposing in this specific environment.
Is there any evidence of their accumulation in marine life? Or is it too early to determine the finalities of where they end up?
We still don’t understand their complete life cycle. We do know that in orders of magnitude they do decompose faster than regular, petroleum-based plastics, whose decomposition takes hundreds of years. But it’s too early to determine exactly what will happen to them in the marine environment if we start to produce them in the same volume we produce conventional plastics today.
We’re talking about the production of polymer molecules by living microorganisms. That involves enzymes with specific jobs making chemical adjustments and transitions. Could we potentially study these organisms’ genetic code and modify them to be able produce whatever we want?
It is a possibility, but not one we are currently pursuing. We don’t yet know enough about the diverse nature of these organisms to use such advanced tools. At this stage we’re looking for new organisms with new polymers, new enzymes which will produce the kind of properties we are looking for. Synthetic biology has tools which enable the manipulation of specific enzyme pathways, so we probably will start doing that in the future, but we must first truly understand what we are working with. We will probably achieve this in a natural way, where a certain microorganism will produce the polymers we need to replace a lot of the polymers currently used in synthetic plastics.
We want to have a library of different biological polymers, where we can use different blends to replace the plastic polymers we are using today.
That means you have to observe an entire population of these microorganisms, look at the polymers they produce, try to isolate a particular strain and then look to culture those to achieve a purity of a particular polymer property that might be desirable.
Exactly. The process is very similar to one we already use today with regular polymers used in plastics. For example, polypropylene is not a single polymer but a library of numerous polymers with specific numbers and specific properties that we build off of for use in composite materials. We need to create such libraries from marine organisms and combine multiple polymers with differing properties
Compare for me the properties of synthetic polymers and seaweed based biopolymers.
We are currently mainly analyzing thermal and mechanical properties. We can surmise that we need to make blends in order to achieve properties close to the ones in synthetic polymers. We use not only PHAs, but also different mixtures of PHA and PLA, for example, polylactic acid, to achieve flexibility. For very robust material, we use less PLA; for small materials, we probably need more PLA. These are the pathways we are looking into.
So you’re claiming that if you get those mixture proportions correct you can easily reproduce important properties that we can achieve with synthetic polymers?
That’s what we’re aiming to achieve. We want to have a library of different biological polymers, where we can use different blends to replace the plastic polymers we are using today.
One challenge that I am aware of for bioplastics is their porosity to gases and fluids, which could prevent their wide-scale use in, for example, food packaging and medicinal applications. Is that the case?
I think it’s too early to come to such conclusions. Bioplastic research is still in its infancy. With more time and effort being invested, I have no doubt that the polymers will overcome these challenges. One advantage of using archaea bacteria is that they don’t contain endotoxins. When you create the same polymer in bacteria, you need to get rid of endotoxins, rendering medicinal usage challenging. Since archaea don’t contain endotoxins by nature, they don’t present this problem. This is a prime example of how choosing a different organism can give you the same polymer without added complexities.
You’re painting an optimistic picture of what could be in the future for these materials. Ultimately, however, we have to talk about volume and capacity. Using this technology, will we be able to produce a high volume at low cost?
Let’s look at polylactic acid as an example. Polylactic acid is a synthesized polymer, but it’s initially produced by fermentation, so it’s of a biological origin. This polymer already makes up about one percent of global plastic production, a significant amount for a biologically derived material. Given the developmental processes which are currently taking place and will enable low-cost production of these polymers, I think it will be possible to achieve high volumes in the future.
What is the future?
The future is about timing. It took us about a hundred years to get to where we are today with plastic materials. We cannot afford another hundred years to develop biologically degradable, biologically derived plastics. We need to condense it into five or ten years. We need to be able to replace the majority of plastic production with biologically derived and biodegradable materials within about ten years. So that’s the challenge.
Who’s going to drive that? Companies who are currently involved in polymer production? Will it ultimately be down to consumers? Will it be government legislation?
We need a triangle of consumers, legislation and big companies. It’s impossible to achieve this goal without all three working together. Multiple environmentally friendly projects show us that without proper legislation, it’s almost impossible to penetrate the market. Both legislators and big companies are influenced by consumers. If the majority of people say that they want these materials, legislation will move very fast. Companies will follow, because they want to sell their product and it’s the people who decide what to buy.
Guest: Alexander Goldberg
Alexander Goldberg received his PhD in Bioengineering from the Hebrew University of Jerusalem. Dr. Golberg interests are in biological systems engineering, bioenergy, macroalgae biorefineries, new sources for food, chemicals, fuels from macroalgae, energy and applied thermodynamics, droplet microfluidics and electroporation. His water research related projects deal with bio-sensors using microfluidics devices and bioremediation technologies with macrophytes.
Host: Michael Londesborough
Michael Londesborough received his Ph.D in chemistry from the University of Leeds. He is chairman of the Czech Academy of Science’s Institute of Inorganic Chemistry in Řež. He collaborates on popularization projects of the Czech Academy of Sciences, Czech Television and the National Technical Museum.
Watch the interview with Alexander Goldberg (19 min)
Source: Unipetrol's “Let’s Talk about It” project site.
The aim of this discussion platform is to highlight areas such as the circular economy, alternative fuels, recycling, responsible production and corporate social responsibility.