Design Life-Cycle

 Patrick Lumauod
4 December, 2019

Plastic Roads Materials

Plastic roads are exactly what they sound like, they are roads made primarily of plastic. To be more specific, they are made of recycled waste plastics such as water bottles and straws, or in some designs with rubber taken from everyday items such as bike tires. The reason for its development is relevant now more than ever, with our growing worldwide epidemic with the rise of excess overflowing in landfills both on land and in the ocean. As a result, to counter issues like these, plastic roads were developed as a plausible answer to these modern day problems. Given how much plastic is used during the production, and how reusable it presents itself to be during maintenance, they serve to be one of the potential leading products to fight against environmental pollution. As of now plastic roads are seen to be one of the most efficient means of waste recycling presently, with the goal to reduce plastic and rubber buildup in landfills around the world. With little waste emission and consistent sources of materials always at hand, plastic roads are able to increase production routinely without the need to cut down on valuable resources that can be allocated better elsewhere.

Why is this Relevant

When we consider today’s ever growing issues that are global warming and environmental pollution, the idea to reduce the amount of plastic waste through reclamation and reuse, was a huge selling point for the kickoff that is now known as the plastic road. When we compare the modern asphalt or concrete road/sidewalk to this alternative, it has shown that these roads are not only environmentally friendly, relatively speaking, but are incredibly durable as well. These attributes can only be attributed to their material makeup and choice of resources used for the production of the roads. There are two main resources used in its creation, and that is plastic and asphalt. In a basic sense, plastic roads are just a melted down mixture of the two materials which are repurposed and molded to fit the need for sustainable roads. Sustainable being the key term here, given that these roads are 100% recyclable and have a much better wear resistance compared to standard asphalt roads. Since a large portion of the road is made of plastic, and incapable of absorbing water, it is able to effectively fight against water weathering and abrasion, which would reduce costs during maintenance or upkeep. Added to the fact that the roads are incredibly flexible and able to keep a good smooth surface for a large period of time.

Manufacturing

The Plastic used during the production of these roads, comes directly from plastic waste dumps or landfills straight to the manufacturing facility, wherever it may be. The road variant in question is the one designed by Dr Rajagopalan Vasudevan in India. His road, to put it simply, is made by melting each material and mixing them. This mixture is then poured out and left to dry. With this, a large portion of the plastic used for the creation of these roads comes directly from India’s waste dumps. With Its transportation primarily relying on the use of automobiles and human labor to transfer and carry the materials over to the factory. The production process is made up of several stages: the wet process, the dry process, the preparation process, and finally the actual process. These stages follow the line of material acquisition, material evaluation, material processing, and road production.

The wet process revolves around material gathering, during the roads experimental phase, different types of plastics were selected to help determine which would be suitable for actual production. In this case low and high density polyethylene (LDPE, HDPE), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and acrylonitrile butadiene styrene (ABS) were chosen. These plastics can be found from a variety of products such as plastic water bottles, straws, plastic wrap, packaging, plumbing pipes, and electronics such as mobile phones and laptops. However, despite the large quantities of these plastics found in India, not all are suitable for the required needs found when mixing with the bitumen. Whether they are of sufficient makeup comes down to the melting point and density of the plastic. Such requirements allow roads to be made more durable with strong binding properties and reduce toxic chemicals creating from heating by using plastics with high temperature ranges.

Within the preparation phase, waste plastics are cleaned up and processed for proper mixing. During this stage, the plastic is washed, shredded, agglomerated, extruded and granulated before it enters the vat. Previous tests had a mixture made up of the previously mentioned plastics alongside two different grades of bitumen, 60/70 bitumen and 80/100 bitumen. The grade of bitumen correlates to its penetration and hardness. This is measured by penetrating the bitumen with a loaded needle over the course of five seconds, the depth of the needle following the test depicts the grade. In the case of plastic roads, 60/70 and 80/100 grade

bitumen are semi-hard grades used primarily for road construction. This is immediately followed by the dry process in which aggregates of rock or gravel are coated with a layer of melted plastic, which is designed in order to increase the binding properties of the road and increase the strength of the pavement.

During the actual process, specific measurements are taken into account when considering how much of each resource is required when making the road. Generally, the sheared plastic should only make up around 10-15% by wt. per aggregate and the mixture is to be heated from around 160-170 oC. With the bitumen mixture being heated to 160 oC. The heated product comes out as a mixture of gravel, bitumen, and plastic which is to be poured directly on the ground for drying. These hot mixtures are transported to their requested locations traditionally using a paving truck. However, Paving trucks are incredibly fuel inefficient, only capable of averaging around 6 mpg creating plenty of carbon monoxide emission during its usage. Such trucks release the raw road along a line, whilst simultaneously smoothing it out for future use.

Production of the Material

As is now known, these roads are made of primarily plastic and bitumen. However, these materials originated elsewhere and were originally created to serve a different purpose. In the case of water bottles they are made of polyethylene terephthalate or PET for short, which is a thermoplastic polymer created from petroleum hydrocarbons which can be found in crude oil. Crude oil is unrefined petroleum or a type fossil fuel that can be found dug up beneath our feet. However, the usage of this oil does lead to environmental pollution, which is prevalent in this

case with one of its products, the water bottle. Water bottles are created from petroleum hydrocarbons through a course of reactions with ethylene glycol and terephthalic acid. However, in order to produce water bottles, it must first be polymerized. Which has a habit of creating unwanted wastes such as diethylene glycol and acetaldehyde. Once then could you blow the material into molds and form the water bottle.

Bitumen or asphalt on the other hand is a product of subterranean or surface tar sand which unlike petroleum hydrocarbon, is not a crude oil. Given that tar sand contains elements of nitrogen not found in crude oil. The Bitumen found in tar sand is highly viscous and has a density higher than water at 60 oF. Because of its chemical makeup of hydrocarbons and high molecular density, it is capable of creating strong adhesive bonds at low temperatures between multiple solid surfaces. Bitumen is extracted from the sand using various means such as steam or hot water extraction, thermal cracking or hydrotreating and coking and hydrotreating. It is further refined and mixed with asphalt to hold the aggregates of rock, sand, gravel, etc. together. In the case of plastic roads, the bitumen is obtained by recycling previous roads and repurposing its asphalt into the plastic bitumen mixtures which will take the space that is left by the road removal.

Conclusion

As of now these roads are not in mass production globally and are only in their infant stage of usage around the world. They are currently being used as a test bed for what could eventually come down the line, if plastic control can’t be properly maintained. Then there will be a much more noticeable shift in environmental change that could reach as close to home than we’d rather

experience. For now, these landfills are limited to select areas of the world, some parts of South America, Africa, east Asia, etc. However, a large portion is found directly in India. Roughly 26,000 tonnes of plastic waste is found in there and the country currently stands as the 15 largest polluter of plastic in the world. This creation by Dr Rajagopalan Vasudevan, was a means to repurpose the product as he believed that plastic itself wasn’t the problem, but we as people were. That there was so much more we could do with the material instead as opposed to letting it amass in a worthless trash pile directly outside someone’s home. As of now plastic roads cover about 10,000Km worth of land in India, and that number is still growing today.

Overall, the implementation of plastic roads could be a huge step in decreasing but not eliminating plastic waste. Given its reusability by nature, eventually plastic production will outpace the roads’ life cycle; and only allow it to be a temporary solution to deal the waste we have now. Regardless, it could be a major step to reduce world pollution, if projects like these take off and become standardized in more areas aside from test locations in select few areas. The idea that plastic can be properly recycled without large amounts of carbon emission is already a positive step in the reduction of environmental pollution

Hsiao-han Hung

Professor Cogdell

December 4th, 2019

Plastic Roads Embodied Energy

Plastic roads were first invented by an Indian professor named Rajagopalan Vasudevan. Seeing the trash which littered the nearby neighborhoods and came washed up on shore, Vasudevan created an alternative road mix composed of  melted down plastics bonded to asphalt. The lifespan of a plastic road has never been fully documented from beginning to end as it’s only been used in a few working roads since 2016. The embodied energy that goes into the life cycle of plastic roads claims to be a significant reduction from asphalt roads, but seeing as the product has not been fully implemented yet, there’s much more involved in production revealing that the plastic road may not be as Eco-friendly in its embodied energy from the raw material acquisition to waste as it may seem.

In Vasudevan’s original creation of the plastic road, he, with the help of many others, acquired excess plastic found in towns, rivers, and coastlines to create his new pavement mixture.  At the time being, mostly renewable energy sources and animate movers were used to collect the plastic waste. Then there is the energy involved in either of the two types of processes involved in making the road mixture: wet and dry. The wet process first involves the segregation and shredding of plastic waste which is washed, and granulated. The bitumen is imported from Mumbai to Tamil Nadu, India, which is approximately 669 miles apart which is equivalent to a 1.2 hour plane ride. Using a Boeing 747 as reference, a single trip to Tamil Nadu would burn about 3,900 gallons of fuel each time. During the mixing process the plastic will be melted in with the bitumen continuously at approximately 180 degrees Celsius and stirred until cooled to about 150 degrees Celsius. It should be mentioned that the plastic and bitumen are heated separately before being combined, and due to the high heat and pressure necessary, this is the most energy extensive part of the process. Aggregates from a local quarry are mixed in which are being transported by truck. The aggregates are stacked in cold material loading with transfer machines fueled by diesel and once thoroughly stirred, the plastic-bitumen mix will be complete and ready to be used for laying at 110 degrees Celsius. The mixing alone is estimated to make up a value of 3 mega joules for each kilogram of the mix created. Next is the dry process, which again, begins with collecting and sorting through various types of plastic waste. Once the wastes are separated they are then cleaned, purified and cut using a shredding machine. This process is less energy intensive as once the plastic is melted to 170 degrees Celsius it’s merely poured over the aggregates. Overall, the raw materials acquisition utilizes the network of manpower found in India where people are gathering the plastic waste and separating the materials by hand and is reliant on animate movers with few energy involved. The manufacturing and processing on the other hand requires work from inanimate movers, such as shredders, and mixers, composing of about 75% of the energy consumption in material acquisition and processing combined. Common fuel types involved in the process of making and refining the mix are diesel, hard oils, electricity and coal.

The distribution of the plastic road mixture is nearly identical to that of a regular road. Once the mixture is transported via truck to the construction site, the mix is laid onto the ground with a roller of 8 ton capacity. In recent studies it has been determined that during road construction, the traffic caused by the construction is about 18 times more energy intensive than the construction itself and this study was based off of European roadways. By comparison, the largest city in Europe is Istanbul with a population of 14.7 million people, while Tamil Nadu has a population of 67.8 million people. Suffice to say, the additional fossil fuels burned during traffic is greater in India, however, it’s exactly why the plastic road becomes more efficient. in the long run. The plastic road’s improved durability will reduce the amount of time traffic will be interrupted to replace a road. In one regular overhauling of asphalt roads, the energy necessary to replace them came up to be about 100-300 mega joules which can be avoided several times over with the plastic road. The initial upending of asphalt roads may be energy extensive in the present, however, the longevity of the plastic road and re-usability makes it more efficient.

What most people claim is the most Eco-friendly aspect of the plastic road is that once built they can be recycled and melted down again to be used in newer plastic roads. However, when that plastic is ready to be recycled and how widespread plastic roads will be as a practice is wholly unpredictable. Nonetheless, the melting down of the existing plastic-bitumen road ensures that this long-lasting waste is being reused and not spread into the ecosystem. Ideally, very little or no energy will be used in the acquisition of materials and the recycling process will only consist of reheating the old road pavement. Waste management will be difficult to gauge as the plastic road has yet to reach its full life cycle since it was created relatively recently in 2016. The recycled parts of the plastic is as well an assumption, an intention of what is supposed to happen during the recycling and waste management phase as the first road is still in working condition today.

Alejandra Valladares

4 December, 2019

Waste & Emissions

Building roads with plastic waste is one of many innovations people have come up with to help mitigate the issue of pollution from single-use plastic. There are two different designs for the use of plastic roads, one uses 100% waste-plastics to build modular pieces of road and the other uses current road building methods and materials but adds waste-plastic into the mix which causes some beneficial chemical alterations. For this paper we will focus on the latter.  The idea of plastic in road building is not entirely new, polymer modified bitumen has been used to increase the strength and durability of roads for a while now. Unlike polymer modified bitumen however, plastic roads are made with plastic waste, not new polymers. Plastic roads have been in use for about 15 years in India but they are still in their infancy and remain in the testing phase in most other countries.

The concept of plastic roads was designed to repurpose used plastic and curb waste. The creators claim that their roads will reduce the energy used in construction when compared to conventional roads. They also believe that their roads will be able to be recycled into roads over and over again, giving the product a cyclical life. While the product is intended to have a lower carbon footprint than conventional roads and reduce plastic waste, I want to find out how much energy goes into the construction of each plastic road unit from acquiring plastic, melting it and mixing with bitumen, to transporting it to a construction site and laying it down. I also want to find out about any pollution that may arise during use and exposure to wear and tear from the elements. Adding trash to an existing product and getting a better product out of it, and with fewer emissions sounds too good to be true so I want to learn whether these claims are credible or not.

The 3 main materials that make up plastic roads are gravel, asphalt (also known as bitumen) and waste plastic, usually single-use plastics that have served their purpose. Although it sounds like plastic roads would be solving the plastic problem, plastic roads only divert plastic from landfills but encourage another fossil fuel dependent activity - driving. Finding a “solution” to the plastic problem might encourage the production of plastic by leading people to believe that as long as they recycle it, plastic is fine to use freely. One article I found discussed the difficulty that some companies face when trying to source waste-plastic. People do not always want to sort their garbage so even in places riddled with plastic waste, it is not a streamlined process to get that plastic back to use. Traditional roads require less work in the sourcing of materials because the infrastructure is already in place. Plastic roads, being so new, may require more work to acquire materials so the 43% of total emissions from traditional road building that comes from acquisition of materials may be higher. 

The same set of emissions from any plastic used in the roads is also a part of the lifecycle of the road itself.  According to IVL, it takes 7,890MJ of energy and 1,100kg of carbon dioxide are released in the manufacturing process of one ton of plastic (Chehovits, 4).On top of this we must consider the production of bitumen. According to Eurobitume, it takes 4,900MJ of energy and emits 285kg of carbon dioxide to manufacturing of one ton of bitumen (Chehovits, 4). These numbers include the energy and emissions for the acquisition (via drilling) and refinement process of raw bitumen.

Manufacturers of plastic roads claim that no toxic emissions are released in the production process because they only heat the plastic to its melting point  of 160ºC. I was not able to get data on how much carbon dioxide is released during the melting process but according to the manager of construction for the city of Vancouver, the use of plastic in an asphalt mix lowers the viscosity of the mix so that it requires a lower working temperature. This leads to a reduction in volatile organic compounds (VOCs) and carbon dioxide released at the manufacturing plant and at the paving site. They also reported lab findings of a 20% decrease in gas used in this process over traditional road making methods (Ridden, p4-5). But these findings contradict MacReber’s statement that there are no emissions during production. Going further, one study found that the levels of diverse aldehydes and resin acids, irritants and carcinogens with sensitizing effects on people exposed to them, were significantly higher when waste plastic was added to the mix (Vaananen et al., p34). The lower temperatures required for manufacturing of plastic roads lead to less emissions overall as it is the heating and mixing of bitumen and gravel that creates about 54% of the total emissions from production of roads (Feng et al). 

Manufacturers also claim that the chemical properties of the plastic are altered during the melting process so that there is no risk of microplastics from the roads getting into the environment. This source, the manufacturer, does not seem too reliable however and there does not appear to be any proof of this. Whole pieces of road could potentially crumble off during the process of recycling or repairing the plastic roads and I believe that this is where plastic and bitumen could enter the surrounding environment. I was not able to find much information on whether the plastic is modified enough to prevent the possibility of microplastics being littered into the environment but it seems to me that this claim is just based on the fact that the plastic is modified into something else that does not necessarily fit under the title of microplastic. Throughout the research process I ran into this problem of credibility a few times because much of the information published about plastic roads is written by the manufacturers of the roads. 

If we want to take into consideration the emissions from the machines used to coat gravel and bitumen, we should look at the machines transporting the material to the site. The waste and emissions during transport of road/materials to paving site are pretty comparable to traditional roads but there have been lab findings of reduced amounts of greenhouse gasses produced during the rolling-out process compared to traditional roads  (Ridden, p4-5).

One great aspect of the plastic roads is that they can be reused. There is not much data on the reuse of plastic roads since the oldest roads are still in pretty good shape but 99% of all roads are already recycled into new roads so this is nothing new and the claims that manufacturers make are probably true here. The plastic roads have a projected lifespan that is three times as long as traditional roads so the emissions from recycling and maintenance are lower than with traditional roads but these numbers have not been tested with roads, only other petroleum products that have had waste plastic added to them have been found to have longer lifespans when compared to traditional products.

While plastic roads seem to provide a promising way to recycle some plastics that are currently un-recyclable, they do not solve the problem of single-use plastic or the deeper problem of human’s complete dependence on fossil fuels. The addition of plastic into the mix of asphalt and gravel that make up the road results in lower emissions but creates new fumes that are not only greenhouse gasses but are also carcinogens and dangerous to the workers exposed to the heated mixture during the formation of the roads. This clearly shows us that plastic roads are only a temporary fix to a larger problem, we are able to divert waste from landfills but we create more emissions. They may make us feel better about ourselves for the short-term but the fact is that we are not really able to recycle plastic without using more fossil fuels and encouraging more fossil fuel use. The only real solution I see is to find an alternative material to use with a lower carbon footprint than plastic and to improve our transportation infrastructure.