A think piece by Katherine Adams, Technical Associate, ASBP
Choosing what materials and products to use for the multitude of applications in construction is not always straightforward – not least when you need to ensure they are fit for purpose. One important aspect to consider is the type of material that is used, its environmental impact and in some cases, its recycled content. In the case of plastics, there are many end-uses for recycled plastic in construction which can provide an excellent opportunity to remove circulation of plastics into waste streams for many years. However, we do need to be careful; these applications should act as a means of cleaning up our existing legacy of plastic waste and not perversely encourage the use of more and more plastic. We need to turn down the tap for virgin plastic and focus on plastic-free alternatives where viable.
Plastics, as we know, are used in many applications in the construction sector. Some are long lived, and some are short lived, some are highly successful, whilst others may provide cause for concern.
Plastic production has grown rapidly – with one study estimating that the global production of resins and fibres increased from 2 million tonnes in 1950 to 380 million tonnes in 2015 .
As the growth in the use of plastic products continues there are opportunities to increase their recycled content. This is already happening in some applications, for example, certain types of pipes can contain up to 40% recycled content; PVC for cabling can contain up to 50% recycled content and vinyl flooring up to 60%. There are a few plastic construction products, in fact, which can be made from 100% recycled plastic with some of this recyclate coming from our household waste stream.
In these situations, the construction sector is acting as ‘sink’ for waste plastics, utilising recycled plastics as a raw material and helping to improve domestic waste recycling rates. This is much needed, as we create a lot of plastic waste in the UK with an estimated 3.4 million tonnes in 2017, a third of which is sent to landfill, a third sent to incineration and a third for recycling (and of this recycling – two thirds – 0.7 tonnes is exported which brings its own concerns about how it is managed). 
There is now much more attention paid to the environmental impact of construction, albeit largely focused on carbon reduction and the necessity to reach net zero. There is a greater awareness of the embodied carbon impacts of products and one way of lowering embodied carbon is to increase recycled content. Plastic products with recycled content should have a lower impact than those from a virgin feedstock, but not necessarily lower than alternative products (e.g. ones made from natural materials). Using recycled plastics in products can also be part of a circular economy strategy.
As yet, there is no specific focus on increasing the recycled content of plastics used in construction, but the above drivers are bound to encourage this. The Government is also encouraging more recycled content, with a tax on the production and import of plastic packaging of £200/tonne with less than 30% recycled content . The European Union, in their new Circular Economy Action plan, also are looking to introduce mandatory requirements for recycled content and waste reduction measures for packaging and construction materials .
So, this all sounds great – so what is the problem? Well there are a few. It could be that by focusing on increasing the recycled content of plastic products, we are not addressing other (more important?) issues. Using recycled plastics in construction could be seen an ‘easy’ option and if it acts as feedstock, there is little incentive to reduce it. For example, if we continue to use plastic products (albeit with more recycled content) where viable alternatives exist, this adds to the demand and growth in plastics.
An estimated 6% of global oil production is devoted to the production of plastics, contributing towards considerable greenhouse gas emissions. 
The plastic products we use in construction, will at some point end up as waste, and, as already mentioned, we do not have enough capacity to deal with the plastic waste that we generate. Whilst it is difficult to know the source of plastic which ends up polluting the oceans, we still need to address how to manage it better.
Recycled plastic in construction, could be seen as downcycling (lowering the value of the material). For example, is it better to make a plastic bottle into another bottle or use it as an aggregate for road construction? I mention roads as there are a few examples of where these have been constructed using recycled plastic by mixing it into the asphalt . However, a 2019 report from Austroads  highlighted some potential issues of this application:
“…there are concerns about hazards road workers could be exposed to while handling recycled plastics… Some plastics, when heated, release toxic emissions such as chloride, formaldehyde, toluene and ethylbenzene. Another major concern is microplastics leaching out from our pavements into waterways, posing a serious threat to our marine life.”
From a health point of view, there are concerns with some of the chemicals that are used in plastic products and by recycling them, these chemicals remain in the product. This has recently come to the fore with the recycling of PVC, whereby the EU Parliament has recently blocked the use of recycled PVC containing legacy lead substances . This ultimately means that these products will now have to either be incinerated or landfilled (in the EU). The burning of plastics is also an issue, with research showing that the widespread use of combustible materials increases the growth and severity of fires and produces a higher concentration of toxicants .
Some types of plastics, such as foam ones, are very hard to recycle although technology is being developed. There can also be limitations on how many times certain polymers can be recycled. And just because a plastic product has recycled content, this does not mean it is recyclable at end of life. For example, wood polymer composites, used in flooring, decking, benches, outdoor furniture, walls and planters, could be problematic at end of life.
To conclude, if we are to continue to use plastic products in construction, then it is better if they contain recycled content. However, it should not stop us investigating and developing robust alternatives. We should also be asking questions to those that supply our plastic products and packaging with regards to where the plastic comes from (both virgin and recycled), how it can be managed at end of life and their commitments to increase the sustainability of their products.
Since 2019, the ASBP has been running a Plastics in Construction Group. The group is not ‘anti-plastics’ but is committed to identifying solutions and alternatives that can help to reduce the over-use of plastic building products and packaging in the construction industry. We have produced an introductory guide to plastics in construction, a stakeholders and activities map, and ran an Innovation Pitch Series which sought to identify innovative construction products, some of which may contain recycled plastics.
Find out more at at https://asbp.org.uk/group/plastics-in-construction.
 Some of this research was presented at the ASBP Healthy Buildings Conference in 2019.