Plastics: the great sustainability challenge

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When Sir David Attenborough highlighted the extent of plastic pollution, public opinion fundamentally shifted. The concern crossed over to become a mainstream issue.

This mind shift caused a significant packaging revolution with plastic being phased out, but has this come at a cost? Are we making more environmentally safe products, or are we just creating a different environmental crisis? Well, as in many situations the answers to those questions are more complex than they first appear.    

It appears that the industry’s answer is to replace plastic with paper; as paper is instinctively more sustainable. However, this warrants some further thought. The most common way to make paper comes from using wood pulp, which (unless using recycled content) involves chopping down trees, thereby removing them as a natural store of carbon. This in itself might not be an issue; forestry operations can be sustainable, and many are. Established forests will tend to absorb as much CO2 as they release, so in principle it is possible to maintain a carbon neutral position if the forests are well managed with any removed tress subsequently replaced. But unfortunately not all forests are sustainably managed, and a rapid rise in the demand for pulp will likely result in poor forestry practice. Stark contrasts in forest management can be made between areas of Europe (where the forested area has increased by an area the size of Portugal since 1990), and Russia, Brazil or Indonesia where there have been vast loses in forested areas for agriculture, mining, or conversion (to pulp or palm-oil plantations); all of which highlights the critical importance of supplier accreditation.

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Nevertheless, even when sustainably sourced, the processing of raw wood into pulp consumes a range of chemicals such as sodium dithionite, ozone, chlorine dioxide and hydrogen peroxide, as well as plastics such as polyethyleneimine and polyacrylamide. All these chemicals can get caught in the runoff from the paper making process. To remove and dispose of these effectively, large volumes of water are used; the subsequent treatment of which is an energy consuming process. To make a single sheet of A4 paper, up to 20 litres of water can be required 1. It should also be noted that in some nations 10% of all the freshwater goes into the pulping industry. There is potential for this water to be returned to the system, but only after the energy intensive treatment. A further key limitation of paper is that it is not waterproof. This can be addressed through the use of a coating, but this again raises further issues. Is this coating good for the environment? Are you adding another material that makes recycling more challenging?

An alternative approach to the reduction of plastic pollution within the industry is to make the plastic materials themselves biodegradable (i.e. make the plastic behave more like paper). But there are of course challenges here as well. Virgin plastics produced from oil by definition aren’t sustainable, so biomass derived plastics are often considered here instead. The raw ingredients for these tend to be crops such as cane sugar; so we must factor in that this removes land from other crops required for food production, and potentially removes the very forests that are needed to store CO2. Though, perhaps given the current trends to reduce sugar-content in foods, there is an opportunity to transition any excess sugar cane production towards these biodegradable bio-plastic solutions.

Over the last few years, research into biodegradability of plastics has continued to deliver a wide range of products. When considering these, the completeness of degradation, the conditions required for degradation, and the typical speed of degradation are all important factors. Given this, it is crucial for product designers to better understand the end-of-life pathways for such materials. Many products are looking to claim that their products are compostable, but this may only be possible if consumers compost their waste in the right way! Furthermore, getting this wrong can also potentially be the difference between aerobic and anaerobic degradation; the latter producing methane rather than CO2, which has 25 times the global warming potential.

In a final twist, as newly introduced bioplastics intend to mimic current plastics, it can be hard to tell them apart from other plastic waste streams. In many cases this may not present an issue, but specific risks may arise, such as the possibility for PLA to contaminate PET recycling streams as they are challenging to separate from one another.

So, the challenges are multifaceted, and all too often in tension with one another. But these are issues that we have to address if we are to protect the planet we live on. At CDP we are helping our clients navigate this complexity to make their products more sustainable, more cost effective, and more attractive to their customers.



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Dan Mayhew

Senior Laboratory Technician