Biodegradable Plastic: Tackling Pollution with Plant-Based Bioplastics
We hear so much about plastic and how its inability to biodegrade affects the planet, but how can we change the world with a new type of plastic, bioplastic that is.
Plastic pollution is one of the most persistent waste problems affecting mankind and the natural environment. Synthetic plastics do not easily biodegrade, some take hundreds of years to break down, remaining toxic in soil and water. The hunt for a substitute biodegradable plastic or alternative material is now crucial to our efforts to clean up the planet.
More than nine billion tons of synthetic plastics have been made over the past 60 years, but only nine per cent has ever been recycled. Almost seven billion tons ended up as waste – landfill or litter. Even when plastics break down they become microscopic particles, measuring less than 5 mm in size, that persist in the water cycle and food chain.
Single-use plastics present the most pressing problem. Items such as plastic bags, bottles and packaging are often used once and discarded.
Biodegradable plastics are just one solution. Synthetic compounds are made from petrochemical products, but bioplastics can be made from corn or potato starch. These plant products can break down when commercially composted in three to six months. Materials as diverse as vegetable fats, woodchips, straw and recycled food waste can be used to make bioplastics.
Two main types of bioplastics are used in disposable plastics – polylactic acid (PLA) and polyhydroxyalkanoate (PHA). PLA is made from sugars in plant starches such as cassava, sugarcane or corn. It is carbon-neutral (ie, its manufacture has low or no environmental impact), biodegradable and edible. Plastic films, bags, packing and bottles can be made with PLA.
Microorganisms produce natural polyesters such as PHA with a similar structure to plastic. Industrial PHA is made through microbial fermentation of sugar or glucose. It is biodegradable and biocompatible, so it is safe for use in medicine for sutures, bone plates and skin substitutes. PHA products can also be used as packaging material.
While strong lightweight plastics enhance our lives in many ways, bioplastics derived from sources such as plant materials offer a serious alternative. Scientists in the UK say wood waste and sugar beet can be used to make bioplastics. Professor Simon McQueen-Mason at the University of York said the country could replace half of its plastic bottles with just three per cent of its sugar beet crop.
Products that incorporate bioplastics are leading to a wide range of product innovations to tackle the problem of single-use plastic. There are edible water blobs made from seaweed extract to replace water bottles. Plastic-free shampoo pods, edible cutlery made from rice and wheat, and biodegradable bags that dissolve in water made using cassava starch, are all viable alternatives.
The Plant Based Plastics Council promotes bioplastic use as part of the “circular bioeconomy” to reduce plastics in landfill and improve water quality. Other plant-based products include a biodegradable beer six-pack ring made of barley and wheat, and banana waste bioplastic. One study estimates that switching to corn biopolymers alone could reduce the US plastic industry’s greenhouse gas emissions by 25 per cent.
More than half of all plastics ever made have been manufactured in the past 15 years. Around eight million tons of plastic waste finds its way into our oceans ever year. The scale of the problem is growing. There are now massive gyres – floating swirls of plastic waste – in most of the world’s oceans.
As long-lived synthetic plastics break down in the oceans into smaller and smaller particles they become microplastics that are swallowed by fish and other animals. Microplastics find their way into the water cycle and rain down on Earth. They are found in the air, soil, oceans and rivers around the world.
People eat and inhale microplastics daily. Researchers from King’s College London found levels in the city’s rainwater at 20 times greater than measurements from Dongguan in China. The health implications are not clear but studies of air pollution show links with lung disease.
While bioplastics take a tiny fraction of the time of petrochemical plastics to break down when composted, with fewer toxic effects, there is still a question mark over the long-term impact on soils. Some bioplastics can have an adverse effect on the ocean waste problem, breaking down into microplastics the same way as traditional plastics.
Growing crops to create bioplastics is also a relatively inefficient way of making them and has its own environmental impact. Experts point to using waste products rather than food crops to prioritize land use.
Recycling for reuse or commercial composting means building up the infrastructure to do that. Otherwise biodegradable plastics that are not supported by existing recycling plants could end up being burned or put into landfill.
Creating that infrastructural shift towards bioplastics, big packaging companies like Tetra Pak are taking on plant-based polymers to create their products. “Our plant-based polymers are fully traceable to their sugarcane origin,” said vice president of sustainability Mario Abreu. “We see plant-based materials as playing a key role in achieving a low-carbon circular economy.”
Eight of the world’s leading consumer brands have formed the Bioplastic Feedstock Alliance alongside the World Wildlife Fund to create a more sustainable future for the technology. “This alliance will go a long way in ensuring the responsible management of natural resources used to meet the growing demand for bioplastics,” said Erin Simon, director of sustainability R&D at WWF.
Meanwhile the search for plastic substitutes goes on. Companies are investigating how fungi can be used to make furniture – molding into shapes just like plastic – or in packaging, clothing textiles and footwear. Milk-films make great convenience and store-bought food wrappings. Red marine algae and fish waste products are transformed into wrapping and packing. Hemp strengthens its reputation as a ‘wonder material’ and produces durable bioplastic that Henry Ford once used in a prototype car.
Scientists looking to biodegrade plastics could benefit from the chance discovery that wax worms can digest petrochemical products. While this is fascinating and may help in the fight against pollution, the advice remains to use less plastic by avoiding single-use, and reusing and recycling what we already have.