You know that just chucking it in the recycling bin doesn’t solve the problem. In fact, most of it never gets recycled at all. That’s because in our wasteful society, plastic seems like a waste disposal problem instead of a resource.
The world has produced and consumed more plastic since 2000 than in the entire 20th century. Much of it becomes disposable bottles, table service, shopping bags, food packages, and much more.
Disposing of plastic has become an environmental nightmare. Plastic is not a single substance.
The familiar recycling triangle on many plastic products contains the numbers 1 through 7. So are there seven kinds of plastic? No. The number 7 means “none of the above,” a catch-all for who knows how many other kinds of plastic.
Fortunately plenty of companies and inventors are working to find new technologies to separate plastics and clever uses for waste plastic, sorted or unsorted.
Perhaps once these products become better known, people will be more willing to take the effort to recycle it. Here are just a few things we can do with waste plastic.
PET (the plastic with 1 in the recycling triangle) makes excellent polyester. Fabric from plastic is not an experimental concept. Numerous companies make it. Patagonia made its first recycled polyester in 1993.
To name just one product, Duke University and the University of North Carolina are among numerous universities, colleges, and high schools that purchase recycled graduation caps and gowns. Each gown keeps about 23 plastic bottles out of landfills.
Many companies make recycled polyester. Unifi’s Repreve (jointly developed with Polartec) alone uses more than 100 million bottles every year. Both virgin polyester and plastic bottles are made of petroleum. Making fiber from bottles reduces consumption of oil, requires less energy than making it from oil, and reduces carbon dioxide emissions by more than half.
You can look for products made from Repreve and similar fabrics when you shop.
Drive on it
Adding polymers to asphalt makes road building and repair less expensive. Polymer modified asphalt can withstand heavier traffic and heavier vehicles than unmodified asphalt.
It can be used to fill potholes at much colder temperatures than conventional processes, and the patch lasts longer.
Numerous companies make and sell polymers for road building, but cost savings are even greater when the polymers come from waste plastic.
Films (such as the ubiquitous plastic bags from stores), hard foams, and soft foams made from PET, PP (no. 5) and PS (no. 6) are all suitable materials.
Vancouver, British Columbia has found that its use of waste plastic enables mixing asphalt at lower temperatures, allows greater use of reclaimed asphalt, reduces fumes, and saves energy.
Build with it
Fill a plastic bottle with mud, sand, construction debris, or even plastic bags, and it a brick. Bottle bricks can be used in all the same ways as ordinary bricks.
Besides costing much less than standard bricks, bottle bricks are not brittle. Therefore they can absorb abrupt shock loads better.
Buildings made with bottle bricks can cover the bottles with a variety of materials, or leave some or all of the bottles exposed as a design feature. It is even possible to fit LED lights inside some bottles to make a lighted wall.
Plastic bags also make excellent bricks, including even foil-covered snack bags, without stuffing them into a bottle. It is necessary to melt the plastic and pour it into a mold. Like bottle bricks, bricks from melted plastic bags can withstand tremendous pressure.
The technique of making a plastic roof differs from making plastic bricks. It entails cutting off the top and bottom of the bottles and flattening them into sheets. After combining the individual bottles into ribbons, they can be laid on top of a building the same way grass thatch has long been laid. The Reuse Everything Institute is developing a machine to automate the process.
Plastic roofs from bottles have tremendous advantages over other common roofs in tropical countries. They do not attract insects, leak, or collapse in heavy rain like grass roofs. They do not conduct heat and make interiors unbearably hot like tin roofs.
Filter sewage with it
The California-based Human Needs Project has built a new town center in one of twelve villages that make up Kibera, Kenya, Africa’s largest urban slum.
The center includes an innovative wastewater treatment system that relies on 150 thousand discarded plastic bottles.
Kenya’s drinking water has excessive fluoride levels, so many people drink bottled water and then throw the empties on the ground. Kibera lacked not only potable drinking water, but also any kind of sewage system. Wastewater contains bacteria that, given the right environment, will eat all of the contaminants in the water and, theoretically, leave it safe to drink.
All the center’s gray water (most wastewater) and black water (sewage from toilets) gets filtered through a series of filtration tanks filled with sand and plavels—cut up plastic water bottles stuffed into mesh onion bags. The plavels’ high ratio of surface area to volume provides an ideal home for the bacteria to much away on everything that isn’t pure water.
Monitoring the output to make sure it’s pure enough to drink is beyond the scope of the project, so drinking water comes from a well. The recycled wastewater gets used for flushing the toilets and irrigation. Similar centers are planned for the rest of the slum.
The California Department of Transporation has installed a similar system at the Dunnigan rest stop north of Sacramento. It gets about 2,000 visitors every day, who produce 4,000-5,000 gallons of wastewater. That water no longer enters a sewer. The plastic bottle filtration system produces all of the water necessary to flush the rest stop’s toilets.
Just imagine the savings in water, oil, and landfill space if every rest stop in the country used shredded waste plastic to filter and recycle water!
Use it in 3D printers
The advent of 3D printing has the potential to revolutionize technology, but it uses a lot of plastic and releases unhealthy fumes. The world wastes enough plastic as it is, and 3D printing has the potential to add even more to that amount.
Fortunately, recycled HDPE (no. 2, as in milk jugs) makes an excellent 3D printer filament. Researchers at Michigan Technological University have developed an open-source machine that is inexpensive enough that anyone who can afford the printer in the first place can buy one (or make one) to make their own filament.
Eventually, I suppose, 3D printers will become as common as the printer you probably have by your computer. So remember, if you decide to buy one, also to get the machine that lets you make your own filament from your own trash.
Commercial plastic filament is expensive, at least $35 per kilogram. Using a “recyclebot” requires about 10¢ worth of electricity per kilogram of home-made filament.
Dirt cheap 3D printer filament can do more than save money and reduce the volume of waste plastic. It has the potential to lift some of the world’s poorest people out of poverty. The 15 million or so people worldwide who pick through trash at open dumps looking for recyclable material typically make less than a dollar per day.
If they had these low-cost machines, they could convert at least some of the recyclable discards into printer filament. The added value could bring them 15 times the income for the same amount of plastic.
Turn it back into oil and gas
Plastic came from oil and can become oil again through a process called pyrolysis. Heating plastic in a chamber with little or no oxygen prevents combustion (which would produce dioxins among other undesirable environmental impacts). Pyrolysis reduces the volume of waste by 50-90%.
Instead, the heat cracks the long plastic molecules to make shorter ones: coke, liquid oil, and gas. The gas can become part of the fuel that operates the system. The easily transported oil can be used directly as fuel, made into diesel or gasoline, or used as feedstock to make new plastic.
Feedstock of PE or PP produces a clean-burning fuel. HDPE (no. 2) and LDPE (no. 4) produce a thicker and heavier fuel that requires additional processing. PVC (no. 3) cannot be used in pyrolysis because it releases chlorine, which will corrode the reactor. PET cannot be used because it releases oxygen into the chamber and slows the process. Pyrolysis is not only a sustainable technology, but also very profitable.
At a much higher heat than pyrolysis, plastic becomes a gas without ever passing through the liquid state. Gasification of plastic produces results primarily in a mixture of hydrogen and carbon monoxide (syngas), which can substitute for natural gas or serve as feedstock for numerous chemicals. The process leaves very little ash or char.
Almost all of the waste input becomes useful raw materials and energy. Gasification does not require any separation of one plastic from another. It works with mixed plastic or contaminated plastic and requires little pre-treatment. Therefore whatever plastic cannot be used for any of the other processes described here can still stay out of the landfill.
The world does not so much have a problem with what to do with waste plastic as with failing to recognize the economic and social benefits of recycling it. Used plastic is an environmental menace only because we treat it as a waste instead of a valuable resource.
Do you know people who think recycling doesn’t matter? Share this post with them.
Plastic on a riverbank. Some rights reserved by Horia Varlan
Repreve chart. Polartec
Vancouver asphalt. Source unknown
Kibera Town Centre. Human Needs Project
Bottle brick wall. Source unknown
3d cube printer. Source unknown
Pyrolysis. Source unknown