The idea of incorporating waste plastic into roads has started to take off in recent years and it鈥檚 easy to see why. Not only does it make practical use of an abundant substance that is troublesome to dispose of, but it can improve performance while also reducing the amount of virgin fossil fuels required.
Companies around the world are acknowledging the benefits. In the UK, Scottish firm MacRebur is a leader in the drive for the use of plastics in roads. In Australia, contractor Downer has also developed a surfacing material that incorporates waste. Meanwhile another contractor, Netherlands-based VolkerWessels, is spearheading a completely different approach, involving the production of prefabricated units.
All three started from a perspective of wanting to keep plastic out of landfill but they have all gone on to develop products that claim advantages over conventional road-building materials. The ethos of reuse also extends to the future; all three companies make a point of ensuring that their products can one day come full circle to be recycled into a new road.
Lockerbie-based MacRebur has developed and patented a way to use waste plastic in roads and similar applications such as car parks. Trials of its products have been carried out by local authorities including Cumbria County Council, which is currently leading a government-funded innovation project that seeks to develop the use of waste plastics.
MacRebur鈥檚 UK customers have included Balfour Beatty, which used its material for a cycle lane through the Queen Elizabeth Olympic Park in Stratford; house-builder Springfield which used 20 tonnes at a development in Elgin; and Flintshire County Council, which has worked with Breedon Southern for the resurfacing of a section of road in the Welsh town of Connah鈥檚 Quay.听
MacRebur鈥檚 products are also in use internationally 鈥� including the USA, South Africa, Saudi Arabia, Australia and New Zealand 鈥� through a business model that involves licensing agreements.听
The original inspiration for the MacRebur business came from an enterprising 鈥� if rather alarming 鈥� use in southern India. CEO Toby McCartney was working with a charity helping people to gather potentially reusable items from landfill sites and sell them. He noticed that some of the waste plastics retrieved by the pickers were being put into potholes and set alight, melting to form a makeshift filler.
Thankfully, MacRebur鈥檚 products are rather more sophisticated than this. In 2016, McCartney got together with his friends Gordon Reid and Nick Burnett to launch MacRebur 鈥� the company name is drawn from their surnames 鈥� and they spent 18 months developing a way to use waste plastics safely in roads.
Essentially, the MacRebur product 鈥� comprising granulated waste plastic plus a bonding agent 鈥� is used to reduce the amount of bitumen needed to create asphalt. The company says that its roads look exactly the same as regular asphalt but that the plastic makes them more flexible, enabling them to cope better in a range of situations.
For McCartney, the enhanced performance that the plastic is claimed to achieve is a 鈥渇antastic by-product鈥� rather than the main feature; he prefers people to focus on the environmental benefits. The bitumen is being extended with waste that has no value and would have been destined for landfill or incineration, or perhaps even shipped abroad. Furthermore, the waste is being reused locally rather than being transported far afield.听
鈥淲e sell our product into asphalt manufacturers cheaper than the bitumen that we go in to replace,鈥� says McCartney. 鈥淚t鈥檚 cheaper to manufacture and there are huge cost-savings all down the line.鈥澨�
As part of the production process, MacRebur machinery turns waste plastic into fine granules no more than 5mm in size. 鈥淲e add in what we call an activator, which is a polymer bond that connects the bitumen to the plastic,鈥� says McCartney. The details of the activator are a company secret.
MacRebur produces three mixes to take account of the requirements of different situations. MR10 is the mix typically used where resistance to deformation is needed 鈥� for example at roundabouts. MR6 is the choice for heavily-trafficked roads and MR8 is for car parks or roads with less traffic.听
鈥淭he first product that we made was MR6 and from there we were able to adapt the polymers that we used to do different things to the asphalt,鈥� says McCartney. For instance, a priority in cold places is to reduce cracking whereas hotter countries can find rutting more of a problem.
The amount of plastic used varies. 鈥淲e look to replace an average of 10% of the bitumen content,鈥� he says. This would start at around 3kg in a tonne of asphalt. Each kilometre of road laid using the MR products uses the equivalent weight of 684,000 bottles or 1.8 million single-use plastic bags.
There are approximately 100 different quality grades within the seven internationally-recognised standard categories of plastics, and not all are suitable for this application. In order to produce a sticky binder and ensure there are no microplastics in the mix, MacRebur only uses plastics that melt at a temperature lower than that required to mix asphalt. As a result, it can鈥檛 take all plastic waste but it can use most, including black plastic which is notoriously difficult to recycle.
A further restriction that MacRebur has imposed on itself is that the plastic must be truly waste. 鈥淲e don鈥檛 want anything that can be recycled,鈥� says McCartney. 鈥淚f it鈥檚 a plastic water bottle and that can be turned back into a plastic water bottle then we won鈥檛 use it. If it鈥檚 destined for landfill or incineration, that鈥檚 the kind of plastic that we want.鈥� There is no shortage of input materials, however; 鈥渦nfortunately for the world, most plastic is not recycled,鈥� he says.听
MacRebur鈥檚 products have already been installed on a number of local authority roads in what have been classed as trials. Further development is being carried out under a research programme run by the Association of Directors of Environment, Economy, Planning & Transport (Adept). Under the programme, the Department for Transport is providing funding for a range of innovations across the road network.听
Cumbria County Council secured a grant of 拢1.6m to work with MacRebur on developing the use of waste plastics across all applications from minor patching and pothole repairs through to major surfacing. Asphalt manufacturers Hanson and Aggregate Industries and consultant WSP are among those involved in the Cumbria project. As well as extending Cumbria鈥檚 existing trials, the work is also intended to produce guidance on the use of waste plastics in roads.听
As part of the project, a 200m stretch of Lowther Street in Carlisle was surfaced over two nights in early July. It is the first stretch of road surfacing featuring MacRebur鈥檚 product to have been paid for by the DfT.
The Adept project, which runs until November 2021, is not just about innovation to enhance the physical road; it is also looking at aspects such as the business model, the kinds of waste plastic available and how much can be used. McCartney hopes to prove that waste-polymer-modified bitumen is a viable option for every local authority as an alternative to standard bitumen or polymer-modified bitumen.听
Major Australian contractor Downer has also developed a road surfacing material that incorporates soft plastics 鈥� as well as other waste 鈥� and has secured approval for its use.听
Downer maintains more than 33,000km of road in Australia and more than 25,000km in New Zealand. The company is also a leading manufacturer and supplier of bitumen-based products. A business within Downer, Reconomy, is focused on landfill avoidance and repurposing. 鈥淲e provide a range of services internally and externally to support our customers to increase their sustainable and circular economy activity,鈥� says the general manager of Downer鈥檚 Reconomy business, Jim Appleby.听
The road surfacing product, Reconophalt, contains a high proportion of recycled materials such as soft plastics, toner and glass.听
Reconophalt comes in a range of blends, as it can incorporate different constituents and different recycled percentages, depending on the customer鈥檚 needs. Soft plastic and toner provide the addition of polymers, which increase the performance of the asphalt, says Appleby. The glass is used as a natural replacement for sand, which is becoming increasingly costly to obtain.
Each tonne of Reconophalt contains over 800 soft plastic items, 252 glass bottles and the residual toner from over 20 printer cartridges, says Appleby. 鈥淲e don鈥檛 use plastic bottles. We use soft, 鈥榮crunchable鈥� plastic 鈥� the sort you can scrunch into a ball. This includes a lot of food packaging,鈥� he says. The soft plastic is sourced from supermarket collections and converted via a highly-controlled process into an additive for inclusion in asphalt.
Reconophalt is laid in the same way that all other asphalts are laid and has been used on all types of road 鈥� council, state and strategic infrastructure 鈥� across Australia. 鈥淩econophalt has been extensively tested domestically and overseas to ensure it exceeds the performance criteria of a virgin asphalt, but also has no negative environmental impact,鈥� says Appleby.听
The New South Wales (NSW) Environment Protection Authority (EPA) has recently approved Reconophalt鈥檚 use following an extensive testing programme to ensure both performance and a positive environmental legacy. NSW has specific legislation that requires any repurposed waste material to be approved by the EPA prior to its use.听
May 2020 saw the second anniversary of the first road in Australia that had been laid with Reconophalt. In that two-year period Downer has laid over 77,000 tonnes on roads in six states or territories. 鈥淲e are in discussion to extend the product beyond Australia to provide the positive impact Reconophalt provides on a wider scale,鈥� says Appleby. 鈥淲hen Reconophalt reaches the end of its life it will be able to be removed and reused within asphalt production again and again.鈥�
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