The problem with bioplastics

The argument for bioplastics

The biggest draw of bioplastic is that it uses more renewable resources (biological material – or biomass – which can be replenished) in its production, instead of fossil fuels, and is therefore responsible for fewer carbon emissions. Bioplastic will release carbon upon disposal, but only the carbon that the biological matter sequestered while it was growing.

A number of studies support this argument, with one indicating that switching all US plastics to corn or grass-based products would cut the industry’s greenhouse gas (GHG) emissions by 25%. Advocates also argue that since biomass is renewable, it can be grown all over the world and support agrarian economies. This contrasts with fossil fuel feedstocks like oil and gas, which tend to be concentrated in localised areas and owned by large multinationals or governments.

The biggest potential area of impact for bioplastic is in the food industry. Packaging food items in bioplastic means that the packaging material and any residual food or liquid stuck to it could – in theory – be composted altogether. At present, a lot of food packaging waste is sent to landfill as it is unsuitable for recycling because it is contaminated with food. So, in theory, composting bioplastics might reduce the amount of plastic  and food waste being sent to landfill However, this is only feasible if materials are properly sorted and can be industrially composted, and as we’ll see below, this isn’t always the case.

The argument against bioplastics

While it may be the case that bioplastic has an overall lower GHG footprint than its petroleum-based counterpart, it comes with a number of additional environmental considerations.

Firstly, a large volume of crops, land and water is needed to make bioplastic. As one study indicates, making just one tonne of PLA requires 2.39 tonnes of maize, 0.37 hectares of land and 2.9m litres of water. While these resources could, technically, be sourced anywhere, the vast majority will come from developing nations which are already facing increased loss of natural habitats, pollution, conflicts of land and food and water shortages. One of the biggest arguments from critics of bioplastics (and, similarly, biofuels) is that growing biomass depletes the land available to grow food, and with the global population set to hit 10 billion in the coming decades, food insecurity is a deepening challenge.

Then there are issues of toxicity. While bioplastic is comprised mainly of ‘natural’ ingredients, it still requires a host of chemicals to create the characteristics (strength, rigidity, and so on) that enable it to perform like regular plastic. The toxicity of these chemicals varies, but one literature review – which examined around 20 scientific papers on the matter – found that bio-based plastics are just as toxic as their petroleum-based counterparts.

But perhaps the biggest challenge around bioplastics is that any inherent benefits can only be realised if the material is disposed of correctly. As evidenced above, the term ‘bioplastic’ is confusing – if not misleading – to consumers, who may mistakenly assume such a product will break down as easily and naturally as banana skins or apple cores.

If bioplastics end up in landfill, without enough oxygen to break them down they can last for decades and release methane, a GHG 30 times more potent than carbon dioxide. If they end up in the general environment or in oceans, they’ll function the same as regular plastic.

This issue is compounded by a global lack of industrial composting facilities equipped to manage these materials, with a growing number of them rejecting bioplastics entirely. There are two reasons for this. Firstly, compostable packaging and bioplastics do not add any valuable nutrients to compost, so these products have a net negative impact on the final product created by these sites. Secondly, consumer confusion around types of plastic and their disposal means a lot of conventional plastic – which can’t be composted – ends up at these sites.

It’s not just consumers, either. The UK Parliament, for example, launched its own dedicated collection for compostable plastics in 2018. But within the scheme’s first seven months, all of the collected material had to be sent for incineration instead because of high levels of contamination from regular plastic.

What are companies doing?

Despite these challenges, a number of major brands continue to explore bioplastics as a means of reducing their environmental impact. Coca-Cola, for example, is pressing on with its PlantBottle initiative, where 30% of each drinks bottle is made from sugar cane and other plants. In 2021 it began experimenting with bottles made from 100% bio-based material.

Mars has tested bio-based chocolate bar wrappers, while coffee brand Lavazza now offers coffee pods that can be (industrially) composted. Meanwhile, UK supermarket Co-op was the first UK retailer to launch certified compostable carrier bags back in 2007, rolling them out to all of its stores in 2021.

Given the many challenges associated with bioplastics, however, greenwashing remains an issue, with critics accusing brands of adopting bioplastics as an easy win instead of doing the more complex and expensive work to tackle the root of the plastics problem. Danone, for example, has been a pioneer in bio-based packaging since 2011, but is now facing legal action from environmental groups for its plastic use and reporting practices.

Is there a role for bioplastics?

Bioplastics are clearly not a panacea to our plastic problems, but that doesn’t mean they can’t play a part in the transition to a greener economy, namely in driving innovation and spurring consumer interest in better environmental behaviour. For example, there is research being conducted on bioplastics made from sugars grown in algae, which would limit the impact on food production, while scientists are working on processes that can make bioplastics more easily compostable.

The reality, however, is that we need to completely rethink our relationship with plastic. According to a report from Pew Charitable Trusts, the only solution to our growing plastics problem is a massive $600bn overhaul of the world’s plastic system that reuses and recycles plastic in a circular economy, along with other, smaller-scale changes – including bioplastics. If its recommendations are adopted, the Pew report says, plastic waste could be reduced by 80% over the next two decades – change on a scale that bioplastics alone will never achieve.