The world is drowning in plastic. It pervades all corners of the planet; we eat it; we breathe it. We need an alternative, truly sustainable packaging. ‘Bioplastics’ are often touted as the panacea of sustainable packing. But what exactly are bioplastics? As it turns out, whatever manufacturers want them to be. With the term being used for materials no more planet-friendly than polluting plastics, we need to separate the good from the bad, the greentech from the greenwash.
What are bioplastics?
A good starting point is the following definition, provided by National Geographic:
“…plastic made from plant or other biological material instead of petroleum…either made by extracting sugar from plants like corn and sugarcane to convert into polylactic acids (PLAs), or from polyhydroxyalkanoates (PHAs) engineered from microorganisms. PLA plastic is commonly used in food packaging, while PHA is often used in medical devices like sutures and cardiovascular patches.”
While this provides an accurate definition, ‘bioplastic’ is subject to the same laws governing all non-patented words: it can be used slightly differently by different individuals and groups. This inevitably means that the term evolves over time, gaining an increasingly wide definition. To fully understand what bioplastics are, we need to break down this deceptively simple word. Let’s begin with precisely what ‘bio’ means; crucially, what it is used to mean.
The prefix ‘bio’ is familiar – recognisable from seemingly eco-friendly terms such as ‘biodegradable’ and ‘biobased’. Herein lies the first problem. A ‘bioplastic’ can refer to a material that is biobased but not biodegradable, as with Coca-cola’s (in)famous plant-based PET Bottle. It can also be used for a biodegradable plastic derived from fossil fuels. One example is PCL, commonly used in drug and food packaging. To add further complexity, ‘bioplastic’ may be used for ‘oxo-biodegradable’ materials, which are conventional plastics supplemented with oxidants to make it easier for environmental microbes to degrade the material.
Turning our attention to the ‘plastic’ in ‘bioplastic’, we begin to get a sense of the issue. For some bioplastics (the aforementioned plant-based PET) renewable materials are used to create precisely the same polymer chains as petro-based plastics. The resulting material is technically identical, and it behaves as such. For other bioplastics, the material fulfils the same function as conventional plastics but behaves differently in the environment. The intention is to provide either a planet-friendly end-of-life plan (biodegradation in industrial compost sites) or a sustainable life-cycle (degradation into reusable parts, recycled in the standard way).
Do any of these materials constitute a genuinely green option for sustainable packaging? Or, alternatively, is the term ‘bioplastic’ being used to cover a multitude of sins?
How ‘sustainable’ is this ‘sustainable packaging’?
Let’s delve into linguistics again. The word ‘sustainable’ literally means that something is able to be maintained at a continuous rate. In the context of materials, this would mean that a supply (hence, an ability to use) will never be depleted. In modern usage, however, ‘sustainable’ tends to refer to something that is environmentally friendly. We therefore need to ask the question: “even if bioplastics are technically sustainable, does this mean they are environmentally friendly?”
What happens to our ‘earth friendly’ coffee cups, bags or straws when we’re finished with them? This is is what is known as the ‘end-of-life’ of a product, and it is here where the scientific community has been especially diligent.
One study is particularly illuminating, directly comparing different types of bioplastics in one of their most recognisable forms: shopping bags. Given that across Europe, 100 billion of these bags are used per year, this is a study that needed doing. Researchers from the International Marine Litter Research Unit at the University of Plymouth compared a conventional plastic bag, a compostable bag, a biodegradable bag, and two types of oxo-biodegradable bags. To test the extent to which they degraded, the bags were monitored for three years in three environments: the sea, the soil and open air. Here’s what they found:
No single type of bag reliably breaks down in all environments over this time period. When buried in earth (approximately replicating common landfill conditions) none of the bags disintegrated. In seawater, only compostable bags disintegrated. Biodegradable, oxo-biodegradable, and conventional plastic bags remained intact after three years. In the open air, all types disintegrated within 9 months.
This, as the researchers were keen to point out, does not constitute a good result in this condition. Oxo-biodegradable plastic differs from regular plastic only in its ability to fragment. Thus, when they disintegrate, the result is simply smaller, more penetrating micro-plastics. As for the biodegradable plastics, because most cities lack industrial composting facilities, most would end up in landfill. This would either mean no degradation or, as they are deprived of oxygen, the releasing of methane (a greenhouse gas) as they break down.
This means that if the potential benefits of bioplastics are overstated, there could be actively harmful effects. Overconfidence can lead to complacency, which leads to irresponsible behaviour. A recent report by the UNEP found that items labelled with the prefix ‘bio’ are more likely to end up as litter, with the public assuming this to be harmless. Evidently, this is far from always being the case. Even where bioplastics have a relatively good end-of-life plan, this is only true if they end their life where the manufacturers intend.
For an overview of the current science, this article provides a reliable source.
‘Sustainable’ production does not mean planet-friendly production
We’ve focused on end-of-life, but what about the beginning of the life-cycle? The results are mixed. Columbia University report that bioplastics do, over the course of their lifetime, produce far fewer greenhouse gases than their traditional counterparts. If these are corn-based bioplastics, yearly reduction could be 25%. If the bioplastics are produced using renewables, this could be higher than 75%. However, given what we now know, those ‘ifs’ are quite big. As is clear from the biodegradation issues, greenhouse gases are far from the only harmful pollutants.
A 2010 study from the University of Pittsburgh found that, when beginning-of-life is considered, bioplastic production results in a greater level of overall pollution. The use of pesticides and fertilisers to grow crops was actively harmful and extensive land-use is required. The chemical processing required to turn plant-matter into plastic causes more pollution. Perhaps most shockingly, ozone depletion resulting from bioplastic production was far greater than from conventional plastics.
This raises the possibility that bioplastic production has inherited the pitfalls of both intensive agriculture and chemical processing. To avoid the former, the plant sources would need to be organic. To avoid the latter, a far more efficient production method would have to be found. Even if these conditions are met, the overall benefit may only be felt if the bioplastic in question is bio-based, biodegradable and is disposed of in the ideal environment.
The picture painted thus far has not been a promising one for bioplastics. However, necessity is the mother of invention. The concept of a bioplastic is a fantastic one. For this reason, the scientific community has remained focused on its potential. The University of Pittsburgh study, notably, was conducted 11 years ago. So, what progress has been made since then?
New technologies: a new hope?
The industry has come a long way from PLAs, PHAs and oxo-biodegradable plastics. New sources are continually being considered, with some promising candidates.
Dr. Frederik Wurm, a chemist at the Max Planck Institute for Polymer Research in Mainz, Germany, hails Lignin as one of the most promising candidate for bioplastic production. As a by-product of paper production, 70 million tonnes of the mass is produced each year. The incredibly complex and manipulatable structure of lignin means it is ideal for use in 3D printing or to reinforce other bioplastics. A potentially key advantage of biodegradable Lignin over other bioresources is that it doesn’t require extra land, fertilisers or pesticides to produce. It already exists in vast quantities, with the chemical processing relatively minimal.
Waste – a truly sustainable resource
Kartin Chandran of Columbia University has been investigating use of solid and liquid waste for transformation into biodegradable bioplastics. This complex process uses a community of microbes which feed on carbon. This Columbia article provides a neat summary:
His system works by feeding wastewater into a bioreactor. Inside, microorganisms (distinct from the plastic-producing bacteria) convert the waste’s organic carbon into volatile fatty acids. The outflow is then sent to a second bioreactor where the plastic-producing microbes feed on the volatile fatty acids. These microbes are continually subjected to feast phases followed by famine phases, during which they store the carbon molecules as PHA.
This is particularly exciting, not just because it creates a potentially closed loop with waste constituting resource, but because it is economically viable. A big issue of plant-based bioplastics is the relative cost. Due to low oil prices, bio-based alternative costs remain relatively high and incentives for investment low. With Chandran’s approach, not only would there be little money required to make the product, but money could actively be made if producers are paid to take food or water waste away. In one swoop, this eases the perpetual food waste problem and creates a sustainable (in all senses) material.
This is one of many new innovations jumping on the potential of waste. California company Full Cycle Bioplastics generate PHA from food and crop waste, which crucially is fully recyclable, marine bio-degradable and non-toxic at end-of-life. Meanwhile, Pennsylvania’s Renmatrix have created a technology which drastically improves the processing of plant-based bioplastics. By separating sugars from the biomass using water and heat instead of acids, solvents or enzymes, the process is comparatively quick and clean.
There is a lot going on in the world of bioplastics. New sources are being investigated, new means of processing and more efficient methods of processing continually being discovered. The outlook is promising. Is it possible that bioplastics are indeed the future of sustainable packaging?
Currently, 100,000 marine mammals and turtles and 1 million sea birds are killed annually. We’d all like to live in a world where this figure is a flat 0. We also currently live in a world completely reliant on plastic. For these two things to be compatible, and for bioplastic to be a genuinely viable alternative, several things need to happen.
Firstly, the relative cost of plant-based products used for bioplastics needs to be reduced. This could be, as Wurm suggests, done by taxation of less environmentally-friendly materials as part of governmental climate policy. Even in this case, bioplastics are only effective if their entire life-cycle is considered. To truly get a grip on the extent of biodegradability (and the output of this biodegradation) in different environments, a unified standard of degradation needs to be implemented. Once this is in place, the hope is that technologies will continually develop to meet these standards, and materials produced that degrade into biomass in a reasonable time-frame. In this regard, things are looking promising. Finally, then, approaches such as Chandran’s, Renmatrix and Full Cycle need to be championed and incentivised to promote further innovations. With schemes such as the UK’s Sustainable Innovation Fund, the scenario in which all of these conditions are met is not impossible.
Are bioplastics the future of sustainable packaging? Potentially. Perhaps, however, a change in mindset regarding disposability and superfluous packaging would be more beneficial. In one way or another, the world needs less plastic.