Jayashree Arcot & Martina Stenzel: Are bioplastics the answer to the future?

Jayashree Arcot is an associate professor in Food and Health, the School of Chemical Engineering at UNSW. She focuses on micronutrients, fortification in foods and bioactives in foods and uses innovative techniques to understand nutrient bioavailability.

Martina Stenzel is an ARC Laureate Fellow and professor in the School of Chemistry at UNSW. She's an expert in designing complex polymers, creating glycopolymers, and developing drug delivery nanoparticles.

Both professors share a passion for tackling food waste, which led them into collaborating on their bioplastic research project. In this interview, with a curious mind, we speak to them about their 10-year journey in bioplastics discovery. 

Could you tell us about your bioplastics research project? 

Martina: Our research project turns ‌surplus banana plants into biodegradable plastic bags. When people think of plastics, they often think of synthetic plastics. But‌ nature provides us with a lot of biopolymers; they can be found in plastics and in your compost bin. I always look at a compost bin thinking, there must be more to it, something we can use.

Jayashree: Australia has a huge banana industry, but only 12% of the banana plant is used for food. There’s a lot of waste material on agricultural land, for e.g., through the process of cutting the banana plant and leaving it on the ground to nourish the soil before the next crop is planted. This is to naturally moisturise the soil. There's still so much waste happening on agricultural land. That's how the banana pseudo-stem came into being.

Martina: We both have a passion for waste. Jayashree had the idea. I put my chemical hat on and thought about how we could isolate and modify it. Chemistry modifies things to become useful, we have to tweak it a little bit. That was more than 10 years ago now. 

A lot of grinding and cutting down the plant to a powder. Then you can start extracting anything that's valuable. That's where the chemicals come in. We used a procedure to isolate nanocellulose from the plants, to create a soft material. We then needed to work out how this material behaves in the environment. We really came full circle in that whole process. 

The process did require chemicals to extract materials from the banana plant. Where possible, we aimed to minimise using harsh chemicals, opting for those that can be recovered or recycled. 

What is the lifecycle of your bioplastics? 

Martina: It’s important that a biodegradable product breaks down into products that wouldn’t contain any microplastics, and degrades down into non-toxic materials. It gets absorbed by nature without leaving any trace. 

The nanocellulose we isolate is basically cellulose, a different morphology which brings superior mechanical properties, but also degrades nicely in the soil without any toxic materials. 

Jayashree: When we started the project in 2012, there weren’t many bioplastic products around. We were still trying to understand some fundamental science as to how the degradation happens. 

In the studies, we put the material into soil for six months. After that time, it had become powdery, and very small pieces were left. Had we left it longer, it would have been completely degraded. We used a micro CT scan, to look at the structure of the material and to see what happened to it. We hypothesised that there were soil microbes eating into the material.

What happened was there were soil microbes, which were actually eating into that particular material, and we could actually identify it under the scan, that there were cavities around the material to tell us clearly that there was a microbial attack of the materials.

Are commercial bioplastics as eco-friendly and degradable as claimed?

Martina: Biodegradable means something gets absorbed by nature without leaving any trace, but the term ‘bioplastics’ is very loosely used today. Companies seem to be using the term to describe what they've come up with, be it made fully from natural sources or not. 

Most commercial bioplastic products are not truly degradable. They fall into pieces, or degrade into toxic compounds. These bioplastics may be blended with petroleum plastics to obtain certain properties, such as flexibility, stability or strength. It could be for hydrophobicity, which is for the material to repel water.

In fact, compostable and biodegradable packaging is currently not permitted in the NSW EPA’s Food Organics & Garden Organics (FOGO) program, as their research showed some compostable products contain harmful chemicals. 

‍Jayashree: If we blended our materials with polystyrene, we could produce something useful and relatively cheap. The cellulose will degrade over time and what’s left are small pieces of polystyrene, which is microplastic. 

Microplastic is a huge problem. We are seeing it in the waterways. Plants absorb microplastic from the soil. This is not where we want to go. While a blended material reduces the amount of synthetic polymers, we don’t know what the long term impact is. It could be as bad as using 100% synthetic plastic.

So you have to be very careful. It’s important that a true bioplastic uses building blocks that are naturally found in nature. You need to create something that not only degrades, but also degrades without any toxic chemicals. So we have something that comes from nature and goes back to nature.

Unless you’re able to know what exactly goes into a particular bioplastic, it's hard to understand whether it's going to be biodegradable or recyclable. It may not degrade at all. 

What factors should be taken into consideration when working with biomaterials?

Martina: In terms of chemical footprint, we need to be aware that every time we produce a material we leave behind a chemical footprint. There is no other way around unless we use a banana leaf as it is. Everything else has been processed in some ways, with chemicals that can be potentially quite harsh. Our aim is to reduce the amount of chemicals we’re using or recycle them.    

Jayashree: When sourcing organic materials, we need to consider ethical sourcing like child labour, modern slavery and responsible land management.

The practice at banana plantation is also a circular practice. As far as we know, in terms of banana waste, farmers actually use banana stalks to decrease the need for water consumption. There is up to 90% of water in the banana stem to be utilised. New shoots will feed on this, requiring less water until the plants mature. The dried stem became manure on the field. 

For our project we sourced our plants from the Royal Botanical Gardens in Sydney. We now work with banana fibre directly, sourced from other companies, which process the raw materials for other purposes including textiles. It saves us time and energy, as processing the materials from bottom up, like getting the stem, drying them and processing them. 

It’s a complex question. If you make a polypropylene film, you know where it comes from, and you know how it's processed. But for something like bioplastics, there are ethical, financial, economic, ecological aspects to consider, besides the product itself. 

What challenges do you face with your innovation? 

Martina: One of the key questions is how can we reduce our environmental footprint to the absolute minimum while maintaining good quality? We experimented with other organic waste like the outer husk of rice and cotton waste. They require a lot more blending with the appropriate material to reach a quality to be usable by the users. 

We also look at how we can reuse the materials. With bioplastics, as you reuse it, it will be exposed to moisture and bacterial absorption. So making it 100% hydrophobic is key but also the most challenging. We're still trying to understand how to make natural material hydrophobic, without blending any synthetic material. 

Jayashree: One of our missions is also to tackle food waste, and that comes with the question of sourcing. Households are the largest contributor to food waste in NSW. A solution could be to turn them into bioplastics. But in the end, we need to be able to source things at a ton scale, not contaminated and relatively stable in terms of quality.   

Back to the sourcing question, how can we make sure the materials are sourced ethically, but also suitable for our needs and safe to use? As mentioned we now source fibre directly from companies, rather than making our own. How can we do that on a large scale? How can the ecosystem support the production? 

‍Martina: All that are barriers to commercialisation. The reason why synthetic plastics are so successful is because they're easy to process and cheap. Natural materials don’t provide us naturally with those qualities that would be suitable for commercial use. So to overcome all the challenges and really get into commercialising innovation, we really need everyone to work together. 

We need funding into further development and building the ecosystem. 

The industries like the idea of biodegradable products, but there's no willingness to put any resources into the development. If we could turn our bioplastics into a product, we may see more traction in it. But we need funding and resources to develop it into a truly sustainable product. We haven’t seen such interest in Australia yet. 

Consumers also need a shift in mindset. They need to understand what goes into a bioplastic product, and be more willing to support better products, even if they need to pay a little more. 

Are bioplastics the answer to the future? 

‍Martina: We don’t know the answer. But I think in the end, it does not matter how good a biomaterial is, it’s not footprint free. Therefore, we should think about how we can reduce our material use in everyday life. Do we really need to put tomatoes in plastic containers? Do we really need this takeaway container?

Jayashree: We went through an era where products were introduced to save time and effort. It has made us lazy. Think of how our ancestors lived. It may require more effort, but it helps us to live sustainably. For example, bring your own coffee cups, compost, and shop at your local farmers markets. 

If you live in Randwick where our university is, join the council’s FOGO food waste recycling program. These are the things we can all do in everyday life. 

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To explore partnership opportunity with Professors Jayashree and Martina, please contact

Jayashree Arcot: j.arcot@unsw.edu.au
Martina Stenzel: m.stenzel@unsw.edu.au

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This interview is part of ReCo Circular Sydney 2023 Series, supported by the City of Sydney Knowledge Exchange Sponsorship program. Explore more free content at: reco.net.au/circular-sydney