The road to reduced landfill: paved with plastics?
What can we do with the piles of plastic that already exist in Nature? Perhaps we could use it to solve another problem that we have. That’s what Toby McCartney is aiming to do with his company MacReber. Chris Smith hear from Toby about his possible solution.
Toby - We take waste plastics, and I think it’s important to say, waste plastics. These aren’t recyclable plastics, these are plastics that are destined for landfill. We take those and we mix them in with an asphalt mix, so a road mix, to replace part of the bitumen which is another form of carbon to make a longer lasting, sometimes stronger, sometimes more elastic road structure that doesn’t pothole as regularly.
Chris - Can you use any kind of plastic for this so it wouldn’t matter if you had a mixture?
Toby - Because of what Steven was saying there, we can’t just take any old plastic and shove it in, it has to what we call it homogenise, it has to mix in well with the remaining of the bitumen that’s in the mix so that it works together to do different things to various different roads. We basically make cakes of various different waste plastics.
Chris - Talk me through the process then. So you take some plastic, how much do you need? What do you do with it to make it road ready, and then how is it deployed in the field - or road even?
Toby - We take those plastics; some of it comes from commercial plastic, waste plastics; some of it comes from a council, so household waste. Most people see a plastic bottle just as a plastic bottle, but actually there’s four different types of polymers, four different plastics within one bottle. You have the bottle that’s made from a particular type of plastic, and then the lid that goes on that’s another type of plastic, and then the wrap that’s another type of plastic.
What we do is we separate them all out and then, as I say, like a cake mix really. In fact, we have three different cake mixes where we put those polymers back together so that they work in to replace part of the bitumen - that’s the oil base, the black stuff that you’ll see in a road. Those pellets that we produce, the cake that we produce that’s added in at the same time as the asphalt is manufactured. So the bitumens taken out and our plastic pellets are then added in.
Chris - Is a bit like biodiesel where you end up where a certain amount is the green version and then there’s some original from oil out of the ground diesel and you get a sort of a mixture, when you do this you get some bitumen with some of your new plastic?
Toby - That’s it, yeah.
Chris - What sort of ratio?
Toby - It just depends on the road type. Again, most people just look at a road and see a road but there’s various different road forms. Some has more bitumen but we replace anywhere between 5 to 20% of the bitumen content that goes into a road. A road’s mainly made up of stone, so aggregates. Maybe 90% is aggregates and then there’s sand and stuff that goes in there but, up to 10% of the content of a road is bitumen itself.
Chris - How does it perform in practice?
Toby - It’s absolutely fantastic. We’ve had trials down now all over the UK. We’re just about to launch in places like Australia. Over in Bahrain we’ve got roads down; in the GCC countries for testing. We have to meet a British and European standard and we overly meet that, so it performs much better than a standard asphalt.
Chris - In what way in terms of wearability, durability, in terms of safety? Put me through all the different parameters are that you assess it by?
Toby - We have three different products, or three different cakes. One of them gives a higher tensile strength, so it makes the road basically stronger so if you’ve got heavy good vehicles and lots of traffic on a road it’s very good to create a stronger road.
Another product adds some flexibility into the roads. Up in say Scotland, or over in Canada where we have lots of freezing conditions, what happens is as we get a lot of rain, the rain gets kind of soaked up into the asphalt and is stored in tiny little air pockets within the asphalt. As that water freezes, and we know the science behind this, that water then expands and often we’ll see on our roads lots of cracks and therefore potholes. One of our products gives and elastic quality, if you like, to the asphalt so it reduces those cracks and, therefore, reduces those potholes.
Chris - What about the environmental impact because one of the reasons people are so concerned about plastics is that where particles, ground up plastic, ends up in the ocean, it then becomes fodder for filter feeders, and it can concentrate other pollutants and things up the food chain as well as being directly toxic for marine animals, and it’s not good on land either? Is there not a danger that if you put lots of plastic on the roads that it’s going to wear down as vehicles go over the road surface and, therefore, it’ll turn into plastic particles that wash into drains and end up in the sea anyway - we’re back to square one?
Toby - Yeah, I think there’s two points here. The first is you have to remember where our plastics are coming from. They are from landfill or destined for landfill, and what happens when that goes to landfill a lot of it’s blown out into our rivers and then off into our oceans as whole plastics. Now we’re taking those plastics and we can only take the ones that homogenise into the bitumen so they become part of the bitumen that’s in the road so there’s no microbeads. You may have heard of microbeads, there’s no plastics present in the road. It becomes part of the bitumen. The roads currently, the bitumen is the binder so that’s the sticky stuff that sticks the stone together. It’s like at the moment we have pritt stick in our roads and what we produce with our asphalt manufacturers is the superglue. If anything, it stops the leaching of that bitumen going off into our rivers.