Bags, pouches, labels, liners, lids. Thin film (or ‘soft’) plastics are everywhere we look. Yet they are among the most harmful for human health and the environment.
In many ways, thin films are the ultimate problem plastic. Usually, they are used only once before being thrown away. They are rarely recycled, meaning a lot of them end up in our soil and oceans.
Three major seaweed plastic startups have the IP we need to stem the tide of thin film waste.
Their biobased, biodegradable films are designed to melt away naturally in the environment, solving one of the biggest barriers to more sustainable packaging.
What are film plastics for?
Thin film plastics are flexible, sheet-like plastics used across multiple industries, like food, agriculture, and fashion. Usually, they are made from the fossil plastic polyethylene.
These films are used to extend the product life of food (the clear wrap around supermarket vegetable trays) and make packaging more user-friendly (yoghurt pot lids, see-through windows on sandwich boxes). Dry cleaners and fashion brands use it as garment bags to protect clothing during transport.
In agriculture, huge spools of thin films are used to wrap hay bales or cover soil to trap nutrients and moisture.
What’s the problem with thin film plastics?
These thin, see-through materials look innocuous. However, they are one of the most dangerous household waste products in terms of health and environmental impacts.
Often, thin films are the only components of food packaging that you can’t put in your home recycling bin. This is because it gets caught in sorting machinery at facilities, causing jams. Usually, they end up either burned or in landfill, releasing toxic byproducts in the process.
Sometimes, local supermarkets offer recycling services specifically for these plastics: consumers drop them off and the shop supposedly takes them to specialist recycling sites.
Shockingly, however, a UK tracking project found the material collected by supermarkets actually ends up burnt – a practice that releases extremely toxic air particles.
Clearly, we need better solutions to thin film plastic waste.
Of course, the most sustainable practice would be to eliminate packaging altogether. However, thin films play a vital role in parts of the food system, such as preserving foods and growing crops in agriculture.
In applications where thin films support food security and sustainability, opting for new, more sustainable materials becomes necessary.
The seaweed startup trio
Many startups have turned to seaweed in order to make more sustainable versions of thin film. These startups include the three most recognisable names in compostable bioplastics: Sway, NotPla, and Zerocircle.
The attractions of seaweed for biomaterials companies are clear. Their natural components like agar, carrageenan, and alginate have gelling and film-forming properties. They also contain biopolymers like cellulose and starch, ideal for bioplastics production.
It is also easy to make materials from seaweed that are compostable or biodegradable, even edible. Unlike petroleum, seaweed is a renewable source. Unlike land plants, they lack the tough woody parts that make terrestrial species so costly to process.
One of the big three startups creating seaweed-based thin films is Sway, whose material is almost indistinguishable from ordinary soft plastic wrapping. In contrast to the conventional material, it decomposes safely and quickly in soil as well as on the home compost heap.
The company’s key technology offering is a seaweed resin, which it has branded TPSe, made from a blend of seaweed and land plants.
India’s Zerocircles takes locally cultivated seaweed and makes it into materials specifically designed to dissolve in ocean water.
An important feature of their plastic pellets is that they can be ‘dropped in’, meaning they can be fed into conventional plastic film-making machinery that usually only works with petroleum plastic pellets. This makes it easier for conventional plastic producers to switch to the material, supporting the scalability of their material.
NotPla, a London startup, is famous for their clear and compostable seaweed-based products designed to replace single-use petroleum plastics in a myriad of packaging applications, from grease-proof lining to plastic bottles and clear sandwich windows.
Seaweed startups accelerate
In 2023, Sway, Zerocircle, and NotPla won first, second, and third respectively in the Tom Ford Plastic Innovation Prize.
The prize was just the first phase of Unwrap the Future, a multi-stage accelerator programme aimed at scaling replacements for non-biodegradable thin film plastics.
The three companies then entered the second phase of the programme in 2024, working with brands like J. Crew, Tom Ford Beauty, and Stella McCartney to test the seaweed packaging for their products.
J. Crew has used Sway’s biopolymer packaging through its distribution centre on products ranging from denim to shoes.
Snowboard company Burton has been testing Sway and Zerocircle’s materials to see whether they can replace the shrink film they currently use and whether they can withstand the temperature and humidity fluctuations that occur as they move through the supply chain.
Meanwhile, designer label Stella Macartney trailed NotPla film with its poly bag supplier.
Thin films in agriculture
One of the biggest end uses for plastic film use is agriculture. The strong, thin and flexible material is ideal for mulching, where farmers trap soil moisture, temperature, and nutrients in the soil by physically covering it.
Agricultural film plastics are generally made from fossil-based polyethylene. They are particularly harmful to human health because mulch on cropland is a major source of soil microplastics. From here, they enter crops and eventually, the human body.
Agricultural films are also very difficult to recycle economically – especially when they are extremely thin.
A safe, compostable agricultural plastic would need to break down in reasonable time into simpler compounds safe for the environment – water, carbon dioxide, methane, and other basic elements.
The hunt for sustainable mulching material
Some bioplastics physically behave much like the organic matter they are made from. This means that once they are used, farmers can crush and bury the material in soil, where natural microorganisms break it down just as they would any other biological material.
Regulation in the EU has been driving up adoption of biodegradable mulch material. In 2018, the European Standard for biodegradable mulch films in agriculture and horticulture was released. In 2024, the EU formally recognised that certain soil biodegradable mulch plastics could be classed as fertilisers and therefore beneficial for the soil.
However, there remain several barriers limiting adoption among farmers. Among them are a lack of knowledge about compostable mulch options. Predictably, cost matters too. Biodegradable mulch is more expensive than petroleum-based plastic films.
To sell biobased mulch material to the agricultural industry, producers will have to focus relentlessly on the cost factor. Already, there can be cost advantages to using compostable mulch. Foremost, they get rid of the need to remove compostable plastic at the end of the growth season, since they are simply buried in the ground. This could lower transport and labour costs.
The innovation gap
Soil-biodegradable mulch films have been in use for more than 20 years, mainly made from polylactic acid (PLA). They are a crucial pathway to more sustainable agriculture and many are tested to strict standards governing soil biodegradability.
However, we still need more research investigating the long-term effects of compostable mulch on the environment. This is because biobased materials can behave in very different ways under realistic field conditions compared to the standardised test conditions normally used for certification.
Research into how biodegradable mulch behaves in soil long term is critical because this material does generate microplastics while they are in the process of decomposing completely.
Microplastics from biodegradable, biobased mulch are unlikely to be anywhere near as permanent as those generated by conventional plastic. However, they can have their own environmental impacts.
Another open research question is how the microplastics behave once rainwater or irrigation washes them into waterways. This is because biodegradable mulch does not necessarily break down at the same rate or in the same way in water as they do in soil.
In general, an innovation gap in thin film plastic for agriculture remains. The industry urgently needs materials proven to break down safely and quickly in a wide range of climates and soil types, with minimal impact on wildlife and soil. At the same time, they will need to offer the cost benefits of conventional plastics.
That’s a wrap
Material innovations in agricultural mulch may be a work in progress. Yet the thin films used in packaging already have technological solutions ready to scale.
Between them, NotPla, Sway, and ZeroCircle have the IP to fully replace fossil-based films in applications where they are necessary to keep products safe, dry, and user-friendly.
Recycling remains an important way to make the packaging industry more sustainable. On its own, however, it cannot solve the issue of plastic waste. Low market prices for these plastics rarely justify the high costs of recycling them.
Thin film plastics are a key area where new biomaterials and recycling can go hand in hand to make the packaging industry greener and safer.