In 2020 alone, 425 megatonnes of plastic waste was generated. Photo: ImageSelect
The plastics industry has major adverse consequences, including litter, microplastics and high CO2 emissions. More sustainable ‘bioplastics’ appear promising, but are no simple solution. The future calls for a balance between environmental impact and functionality.
Plastics. They are functional materials that have become indispensable to modern society. They are cheap and can be used for a wide range of (biological) applications. Thanks to plastics, transmitter collars are waterproof, (bio)medical devices such as pipette tips, syringes and catheters exist, and food freshness is guaranteed. Plastic materials are versatile, and moreover ubiquitous. In 2020, 547 megatonnes of plastic were produced worldwide. Yet that same year, we also collectively generated 425 megatonnes of plastic waste globally (Science, 2024). Only 22 per cent of that ended up being recycled; the rest was sent to general landfill or ‘disappeared’ into the environment.
In addition to environmental pollution, the emissions released during plastic production and waste processing contribute to climate change. The plastics industry is responsible for approximately 5 per cent of total industrial emissions, according to research published in Science on 14 November last year. Scientists agree that the plastics industry must undergo fundamental change to address these problems. Avoiding single-use plastics, reuse and recycling, as well as the use of more sustainable raw materials for plastics production, are frequently proposed partial solutions. The latter – an alternative form of plastic that does not pollute the planet – sounds appealing, of course. But how sustainable is so-called bioplastic really?
‘I actually prefer not to use the word bioplastic’, says Wouter Post, getting straight to the point. Post works as a researcher and project leader at Wageningen University & Research, focusing among other things on the development of new polymers and plastics made from biomass. ‘The term causes quite a lot of confusion. It is an umbrella term for two groups of materials with entirely different properties: biobased and biodegradable plastics.’ He explains that plastic materials can, broadly speaking, be divided into a four-part matrix based on these two properties. ‘Most conventional plastics are made from fossil raw materials, such as crude oil, and are not biodegradable. So-called biobased plastics, by contrast, are not made from finite raw materials but from biomass. Their production does not pump additional carbon into the cycle; net emissions are considerably lower. However, this says nothing about the biodegradability of these materials. The third category, biodegradable plastics, are compostable, but not necessarily made from renewable raw materials. And finally, there are plastics that are both biobased and biodegradable.’
Making the plastics industry as sustainable as possible requires both biobased and biodegradable materials, according to Post. ‘It is important that we are able to combine optimal material properties with optimal biological degradation or recycling at the end of a product’s life.’ According to Post, virtually all current plastic functionalities can be retained in a complete switch to biobased plastic, without any further use of fossil raw materials for plastics production. ‘A great deal is already possible. Technically speaking, it is absolutely feasible; the current debate is largely a matter of cost.’
One potential drawback of switching entirely to biomass as a raw material for plastics is the agricultural land required. Organic waste streams are insufficient to supply the plastics industry in full, which means that crops – such as maize and oilseed rape – would have to be grown specifically for this purpose, leaving less land available for food production. Post notes that the amount of agricultural land needed for a complete system transformation is negligible compared with the total area used by the food industry, particularly for animal feed. ‘I think there is a great deal to be gained there in terms of our eating habits. If we shift our protein sources more from animal to plant-based and do something about the mountains of food we waste every year, we will already be well on our way.’
Zwerfinator
‘The production process for bio-based plastics may be less polluting, but the materials are equally harmful to nature. Besides, everything that ends up in a public bin gets incinerated regardless, so in that case the type of plastic makes no difference either’, observes Dirk Groot, alias the Zwerfinator. Groot has spent years picking up litter every single day. He systematically records data on the items he finds and where he finds them. ‘Most of what I find is packaging from things people eat on the go: wrappers and packets from sweets, biscuits and sandwiches’, he says. By literally mapping litter, he draws the attention of businesses and government to its impact. And with results: Groot’s campaigns have led to policy changes on multiple occasions. ‘Fifty-three per cent of the litter I pick up is plastic; six years ago that figure was still 70 per cent.’ Litter is, in his view, an age-old phenomenon – a problem that cannot realistically be solved. ‘There will always be people who drop their rubbish in the street. When reusable bottles became popular a few years ago, the number of bottles I found on the street stayed exactly the same. The people who now had their own bottle had already been disposing of their waste responsibly before. You can’t reach the careless ones.’
Solving the plastics problem, in Groot’s view, does not begin with more sustainable materials but with a good overarching collection system and a reduction in packaging. ‘Adding ever more new plastic streams gets us nowhere. Steps like that are necessary, but we mustn’t become fixated on them and leave everything else unregulated. I think it is important first and foremost to ensure that the millions of kilograms of plastic we throw away every day are reduced and recycled as much as possible. That business benefits from the simplest possible waste composition – the less sorting that needs to be done, the better.’ Post agrees: ‘When new plastic enters the market, it initially contaminates the waste-processing stream.’
Alongside developing new, more sustainable plastics, Post and his research team are also working on fitting existing plastics into the current recycling system. ‘Redesigning that system is a major challenge. Our team has expertise in new plastic materials that need to be recycled by existing processes but behave slightly differently. We replicate recycling on a small scale, observe what the changes are, and pass on advice about appropriate process adjustments to industry.’ When it comes to finding a solution to the recycling problem, different parties often point the finger at one another. Large-scale studies at the European level are currently examining how this should be handled in the future. Both Post and Groot emphasise that a plastics system that is as circular as possible must be the starting point. Ideally, plastic derived from fossil raw materials would also feed into that cycle. ‘If we already have it, we might as well use it. But’, Post adds, ‘new plastic must come from biomass.’
Coastal protection
Whether biodegradability – the second key criterion in Post’s plastics matrix – should also be an objective depends heavily on the product, he says. ‘For some products, the last thing you want is for the material to degrade quickly; in those cases the persistence of conventional plastic is actually ideal. Plastics are used in coastal protection, for instance, where it is absolutely not the intention for holes to appear in the materials.’ For plastic applications where leakage into the environment cannot be prevented – think agricultural plastics or synthetic clothing – biodegradable plastics are a good option, Post argues. ‘Single-use packaging also carries a high risk of ending up in the environment; that can perfectly well be made from biodegradable material.’
‘When companies opt for compostable plastic, they are often very proud of the fact. It is frequently stated on the packaging’
Groot rarely encounters biodegradable plastics among the litter he collects, but what he does find comes from the food industry. ‘When companies opt for compostable plastic, they are often very proud of the fact. It is frequently stated on the packaging.’ Ten years ago, Groot never came across biodegradable plastics at all. That he does so now is, in his view, a sign that people are trying to change. ‘The fact that people are trying something should be applauded. Things are supposedly impossible all the time – it is important to look at and try what is possible’, argues Groot, who is himself of the opinion that packaging that frequently ends up on the street simply should not be made of plastic, regardless of the type. ‘It still takes a long time to break down, and in the meantime causes all manner of problems.’ The best alternative, in his view, is no packaging at all; paper or cardboard is a perfectly good second choice. When neither of those is an option – as with water-resistant coatings on takeaway food – biodegradable plastic is welcome on Groot’s podium.
How quickly and easily biodegradable plastics actually break down depends, according to Post, on both the material and the environment. There are compostable plastics on the market that degrade naturally in the open environment: polyhydroxyalkanoates (PHAs) are one example. This class of polymers is produced by bacteria. ‘The fat reserves of the bacteria form the basis for these types of polymer’, Post explains. ‘Within two years, PHA in the soil is fully converted into biomass, water and CO2. There are also biodegradable plastics that break down only very slowly in nature and require industrial composting. Polylactic acid (PLA), for instance, is one of the few polymers that is both bio-based and biodegradable, but at present can only be composted rapidly at temperatures above room temperature.’ Further research is needed to establish what environmental impact biodegradable plastics have when they end up as litter in various settings, and whether material modifications can enable polymers such as PLA to break down under more natural conditions.
The extent to which compostable plastics contribute to microplastics – another well-known aspect of this wide-ranging problem – is not yet entirely clear to Post. He does note, however, that there are demonstrable differences compared with conventional plastic materials: ‘Biodegradable plastics also first become microplastics before they are fully broken down. But when you study the same quantity of PHA and conventional plastic in the soil, after a period of time you find fewer PHA microplastics than fossil microplastics – because it continues to break down. The accumulation of microplastics in the environment is harmful; with materials such as PHA, that does not happen.’