Plastic has a bad rep, but it is virtually irreplaceable for some applications, says Dr Anthea Blackburn – we just need to produce it in a more sustainable way
The news coverage of marine wildlife living among plastic bags and bottles has pulled at the world's heartstrings. With media campaigns against plastic pollution gaining impetus, and the general public inundated with a regular flow of distressing headlines, it is hardly surprising that plastic is being perceived as wholly to blame for the planet's environmental crisis.
It is easy to understand why plastic is seen as the villain: of the 6.3bn metric tonnes of the material that has been created since 1950, 80% has found its way into our landfills or oceans. It is little wonder that calls to ban it have gained traction.
A nuanced approach
“Not only does plastic have a wide range of applications, but its properties also make it ideal for a number of uses“
Despite the numerous advantages of single-use plastic, including its energy and resource efficiency, there is no disputing its negative effects. However, we need to maintain caution. While much pollution is caused by single-use plastic, combined with our 'use and throw' mentality, not all plastic is single-use in the short term. This is an important nuance that is often lost in the debate. Plastic is more than just shopping bags and straws; it has a range of uses that are integral to our everyday lives. From thermal undergarments to reusable plastic containers, trainers and mattresses to cars and industrial components, these wide-ranging applications offer significant positives. A blanket ban on plastic would be unfeasible.
Not only does plastic have a wide range of applications, but its properties also make it ideal for a number of uses. As plastic is often cheaper and better suited to certain purposes than other materials, we must not classify it as unequivocally 'bad'. The issue is bad use.
Helping to curb the improper use of plastics is a responsibility all must take, and a change in mindset is already well under way. Consumers are becoming more waste-conscious, turning to reusable coffee cups and water bottles in an effort to reduce throwaway culture. Multinational companies from Lucozade to Lakeland are committing to ensure their plastics are recyclable or compostable, and to incorporate increasing proportions of recycled plastic. The European Commission has proposed a tax on non-recyclable plastic packaging in an effort to curb irresponsible usage.
The plastics industry itself is also endeavouring to produce plastics using more environmentally friendly methods – whether this in the sustainability of raw materials used, the efficiency of manufacture, or in their ability to be more easily recycled.
Modern staple
One plastic that features more in our everyday lives than we may expect is polyurethane (PU). The third most widely used plastic in the world, PU accounts for almost 10% of all plastics produced. It is found in the rigid foams that insulate our homes (reducing heat loss by almost 60% when compared to other insulative materials) and the flexible foams in memory mattresses. PU is also in the coatings that protect our clothing, the adhesives that prevent our shoes from falling apart, and the elastomers that make up the wheels of rollercoasters. Simply put, PU's stability, durability and variety of applications have made it a staple of the modern world. It can't easily be replaced.
Producing PU is an energy and petrochemical-intensive process, and many would be minded to replace it with biodegradable or natural alternatives. While cork and mineral wools may be less carbon-intensive alternatives to PU insulations, more than twice the amount of material is required to prevent the same amount of heat loss as PU foams, so the performance value of these long-life materials should be considered. We also mustn't forget to consider the environmental and societal effects of these materials, including import costs, agricultural demand, and waste profile of such materials.
The production of PU has historically relied upon petrochemical-based feedstocks that make up the polyols inherent in the chemical structure of PU. These polymers are often prepared from epoxides, which are industrially produced using the processes of oxidation or hydrochlorination of an alkene collected as a by-product of oil refinement. This has an enormous carbon footprint; replacing the epoxide feedstock could be an effective approach to greener polyol production.
Finding an alternative
Increasing numbers of polyols are industrially developed from plant oils or compounds, such as castor, cashew, peanut or soy oils, with castor oil being one of the few natural products that does not require chemical modification. While bio-based polyols offer advantages over their wholly petrochemical-based counterparts in terms of the renewable nature of the feedstock, these polyols also put a strain on agricultural resources. Furthermore, natural oil-based polyols require additional processing to remove odour, and often have to be blended with traditional petrochemical-based polyols to achieve comparable properties.
The solution then, lies in finding an alternative feedstock. What if the solution is literally all around us? Carbon dioxide, the molecule seen as most responsible for global warming, offers PU manufacturers an opportunity. The abundance of atmospheric CO2 means that adopting it as a raw material could only be a win-win: with a number of industries and nations taking steps to reduce their carbon footprint, the plastics industry can now follow suit.
When producing polyols this way, for every tonne of epoxide replaced by CO2, a further two tonnes of CO2 could now be avoided. A 50% adoption in the PU market alone could mean close to 10m tonnes of CO2 reduction annually, equivalent to taking more than four million cars off the road. Polyols utilising CO2, known as polyethercarbonates, are increasingly becoming the focus of a number of companies that are endeavouring the reduce their impact upon the planet.
Step in the right direction
There is now catalyst technology that takes this approach one step further, allowing for the bespoke incorporation of CO2 into polyols at industrially relevant temperatures and pressures. This lets polyol producers tailor their products for the needs of their downstream PU users. Incorporating CO2 also offers significant product advantages: the subsequent PU rigid foams have improved flame retardance properties, while coatings, adhesives, sealants and elastomers show increases in their chemical, oil and hydrolytic resistances. Economically, waste CO2 is currently, and is expected to remain, considerably cheaper than its petrochemical-based alternatives. These irrefutable advantages are achievable in all aspects of the production of these sustainable polyols – benefits that are in turn passed through to businesses in the PU industry, as well as their consumers.
The increasing momentum behind the environmental movement is a step in the right direction, and there is no doubt that the plastics crisis must be addressed. But our concerns over plastic pollution should not cloud our judgment and cause us to label all plastics as 'bad'. With so many materials used widely in a variety of applications, a total ban is unworkable. Instead, we ought to keep in mind the environmental and economic benefits that plastics offer and seek more innovative ways to make plastics more sustainably – and use them more responsibly. One solution could lie within the molecular chains that make up plastics themselves.
Dr Anthea Blackburn is senior scientist – catalyst development at Econic Technologies
