Bikes, Bowling Balls and the Delicate Balancing Act That Is Modern Recycling

Reflect on some of the weird stuff you gave and received. Now think about how it is going to have to be disposed of when you're done with it. Yeah, even weirder. JL

John Timmer reports in ars technica:

A lot of technological innovation has gone into figuring out how to take a chaotic mix of items and separate it into relatively pure streams of materials. But being able to do so isn't enough—it has to be made into a sustainable business. So today, a lot of the innovation that is taking place in the recycling industry must dually focus on the economics.
A conveyor belt is keeping material flying past at speeds that require both concentration and rapid eye movement if you wanted to track a single item. Above the constant roar of all the heavy equipment, it's just possible to make out the brief hissing of jets of high-pressure air. Those jets are produced where the conveyor belt ends, and most of the material plunges onto a second belt below. Each hiss, however, causes a carefully chosen item to leap off the end of the belt and soar into a different collection area, where yet another conveyor belt takes it on its way.

The process of carefully choosing which items to sift out is all done without human intervention. It's based on how that object reflects light that's outside the range of human vision.All this is happening within just one of a dozen stations inside a modern recycling center, each of which isolates a single class of materials based on their physical properties. Over the last several decades, recycling has gone from a manual process to an extremely automated one, where things like infrared sensors and small jets of air mix with massive front-end loaders and enormous material balers.
A lot of technological innovation has gone into figuring out how to take a chaotic mix of items and separate it into relatively pure streams of materials. But being able to do so isn't enough—it has to be made into a sustainable business. So today, a lot of the innovation that is taking place in the recycling industry must dually focus on the economics.

Large-scale materials science

Recycled materials are only valuable if they're pure—a collection of a single type of metal or plastic that can serve as a feedstock for manufacturing or other industrial processes. The economics of recycling would actually be spectacular if you could get people to separate out a dozen individual classes of recyclables and then deliver them to a recycling center.
Unfortunately, there'd be almost no recycled materials then, since almost nobody would put in the effort to do all the sorting and carting. In fact, sorting recyclables into anything more than one or two separate streams causes the recycling rate to plunge. Single-stream recycling has a big advantage in transportation terms, as well. When trucks aren't required to have spaces dedicated to individual recyclables, they're more likely to end up completely filled before they bring the material to its destination.Recycling in the US: An off-again, on-again love affair

It became a booming industry despite facing a series of intractable tradeoffs.

That pushes the problem of separating out pure materials to the recycling center itself. Here again, economics limits the choices: the more people involved in carefully distinguishing each type of recyclable, the more expensive the process. For recycling, automation is key. But how can a machine distinguish different types of material and separate each of them out?
The answer is that no one machine can. Instead, a combination of hardware is used with different machines separating out specific classes of material. To get the technical details on how all of these machines operate, we visited each type of hardware at the Sims Municipal Recycling center in Brooklyn and had Eadaoin Quinn explain the process to us.

Smash and grab

As barges and trucks arrive at the facility, the material (often still in its clear bags) is dumped as a single stream onto a large conveyor. It's quickly divided into two streams; having two parallel tracks allows the facility to continue operating even if key pieces of hardware are down for maintenance, Quinn told Ars. Typically, the site is in operation for two eight-hour shifts a day.

Machines use science to separate a stream of waste into valuable raw materials.

The first material to go is glass. Lots of it gets broken during transport; large asymmetric steel rollers break down the rest into small pieces. These simply fall through the cracks and are collected below. The rest of the material is too large and continues on its way. Sims can separate out clear glass for reuse; any colored material is typically used as construction fill.
The next station uses a huge rotating magnet to pull out any ferrous metals, which range from tin cans (which have very little tin) to car parts. The problem here is that some of the metal may be buried under other recyclables that weigh more than the magnet can lift. To overcome this, the magnetic drum is located above a conveyor that's on a vibrating platform. The vibrations give everything in the recycling stream a small boost toward the magnet, allowing it to latch on to the metal.
The vibrating platform is large and heavy enough that it physically shakes the whole facility, and it accounts for a lot of the noise.
Everything that's not attracted to the magnet falls off the conveyor and onto a second one below, moving on into the facility. The rotating drum is set up so its magnetic strength drops on the far side of the platform of its rotation, allowing the metals to drop off into a separate conveyor.
It's not 100 percent effective—Quinn says you'll often see the metal hangers of a city that runs on dry cleaning hook into a plastic bag and carry it off among the metals. But it's a lot better than where things started.
Other metals are sorted by a similar machine. Materials like aluminum aren't natively attracted to magnets, so the hardware uses an electric field to induce enough of an attraction for them to latch on to the drum. Again, most other materials fall immediately off the end of the conveyor and drop onto a new one below; the drum lifts all the remaining metals across to a separate conveyor.

Flatten and blast

With the glass and metals gone and paper in a separate stream, what you're left with is plastic. To us, the average hunk of plastic looks about the same, other than the color. But colors aren't a reliable indication of the chemical characteristics of the plastic—laundry detergent bottles, for example, come in a variety of colors despite the fact that they're generally all made of the same plastic.
But if we could see in the infrared, things would look very different. Many carbon bonds absorb infrared radiation, with the precise wavelength being determined by the precise chemistry of the nearby atoms. Since that chemistry differs between types of polymer, each type of plastic has a distinctive signature in the infrared.
To take advantage of this, the Sims facility has a series of optical scanners. These are reprogrammable so that it's possible to switch one from sorting out HDPE to PET without changing anything else about the processing lines. The optical scanners shine light down from over the conveyor and read the wavelengths that are reflected back to it. That way, it identifies where items with a specific composition are on the conveyor.
For this to actually work, however, items can't be piled on top of each other. So there's a separate piece of machinery placed upstream of the scanner. There, a series of physical barriers and moving plates push items that are stacked on top of each other. By the time the conveyor belt emerges on the far side, everything is in a single layer of flattened plastic items.
The optical scanners are placed a set distance from the end of the conveyor; given that it's moving at a known rate, it's possible to know when a specific item will reach the end of the conveyor, its rough shape, and what it's made of.

Off target

During our trip through the Sunset Park facility, we frequently saw hardware festooned with long trailers of VHS tape—Quinn said it's a constant there. We also saw things like plastic furniture, the remains of a computer keyboard, and a carpet moving down the conveyor belts. So we asked Quinn what the most unusual thing she saw come through the machines."One strange thing we get pretty consistently is bowling balls," she responded.  "It’s very thick rubber with cement inside—definitely not recyclable, but we get them pretty often. They break in our shredder. Our shredder can handle it, but don’t put them in."
Bowling balls were just one of a number of things that Quinn said “we don’t want, and we never told anybody we wanted.” But there are a number of unexpected objects that can go into the recycling in New York City. "Bicycles," Quinn said. "We’re happy to get bicycles. You can put in ovens, refrigerators. They do have to be de-polluted, so they get a Department of Sanitation sticker put on it saying they have CFCs removed or whatever. We’ll keep that separate, pull it to a side, we’ll put it on a barge, send it over to our metal management side of the business, and they’ll send it through big shredders."

At the edge where the conveyor dumps its materials, there's a bar with a series of small holes in it. When a piece of the desired plastic crosses it, these holes let out a blast of compressed air in the region where it passes over the bar. That's enough to flip the plastic over a barrier and into a separate stream. Everything else falls straight down and continues for further sorting.
Bit by bit, as each type of material is pulled out, the remaining stream is increasingly pure. In the end, there's typically nothing but misplaced trash or non-recyclable materials. Sims pulls out plastic bags, too, even though Quinn said that "Plastic bags are something we put a lot of work into separating out, and then there’s hardly anyone who wants to buy them. (They typically export those bags, but Quinn is a strong advocate of shopping with reusable bags.)
None of these systems are 100 percent accurate, however; as a final step, humans get involved. While the mixed recycling stream rockets past the automated hardware, there's a dedicated room where a slower-moving belt takes the final streams past a small group of employees who pluck out any mis-filed material. Quinn said there are about 20 of these quality control specialists on each shift. When they see something misplaced, they have the option of moving it to a different conveyor or, if it's a non-recyclable, dropping it into the trash.
Each conveyor eventually dumps a single material into a large bin. From there, it's sent on to a baler, which bundles it up for shipping.

Designed for flexibility

At Sims, the machines at the heart of this system largely came from Europe. "In general, Europeans have been involved with recycling for a little bit longer, landfill costs are higher, they just put more emphasis into recycling for longer,” Quinn said. So, a lot of the pioneering work in developing this hardware went on over there, and a lot of the hardware in the Sunset Park facility was sourced from European companies.
For the Sunset Park recycling facility, Sims worked with a system integrator that found suppliers for all the different hardware required. Designing the final form looked like a challenge, as the hardware had a very complex, three-dimensional arrangement. Unless you were at the floor or roof level, there were always conveyors moving both above and below you, often heading off at perpendicular angles. This arrangement appears to be very space-efficient; for the amount of equipment present, the facility is remarkably compact.
Despite the intricate arrangement of the hardware, Quinn also said it's designed so that additional sorters could be added if needed. "It’s definitely developed with the idea that markets are always changing; there will be things we’ll want to separate out in the future, things that won’t be worth it to separate out as well."
Existing optical sorters could also be reprogrammed to handle materials they're not currently used for. "This facility has 16 optical scanners; our old facility had four," Quinn told Ars. "So that really opened the number of plastics we’re able to separate out. That also allows us to do more double-checking so we can clean up the material faster."
This flexibility could be critical, as there's been talk of shifting New York City to a single-stream recycling system where paper would be mixed in with the rest of the metals and plastics.
Sims Municipal Recycling also has facilities that handle recycling in Chicago. And it's part of a larger company, Sims Metal Management, that focuses on recycled metals more broadly. A lot of the material comes from larger sources like appliances.

For the most part, the company's bottom line and environmental consciousness go hand-in-hand. The more materials it can recycle, the more products it can sell on to manufacturers. During the last several years, since New York's recycling program restarted, new classes of plastics (such as takeout food containers) have been added to the list of materials that can be recycled, in part because Sims added the capacity to handle them and found buyers for them.Quinn is also part of the company's education program, which frequently hosts school trips at the recycling center. The site has a room filled with interactive displays intended to help them understand what's going on in the hardware we visited. That also could help the company's bottom line. "More than half of everything we should be getting is going straight into landfills or incinerators," Quinn told Ars. "We call it the capture rate—of everything that’s dedicated recyclable, we’re only getting 44 percent."
Getting more of the city's families with the program could start shifting the amount of recycled materials, again helping the company's sales. "That’s all stuff we have the infrastructure to deal with tomorrow if people just started putting it in the bins," Quinn said.
But an environmental ethos seems to run a bit deeper at Sims. It takes a fair bit of energy to have a constant supply of compressed air running to dozens of sorters or to keep a giant metal frame vibrating at a high frequency to help magnetic sorting. But Sims gets some of the needed power from renewable sources. "Our renewable energy on site, from solar panels and from the wind turbine, that covers about 20 percent of our energy needs to power our equipment," Quinn said.
The roof of the facility is covered in photovoltaic panels. With its unobstructed waterfront location, these are probably operating at about the best capacity factor that's possible in New York City.
The site also hosts the city's first commercial-sized wind turbine. It was a windy day when we visited, and the blades were whipping around at a high pace, providing a barely audible whoosh as each blade swung by. But the peaceful operation belies the multi-year struggle it took to get it installed—the city had no permitting process in place for something like that, and getting all the paperwork in place was apparently a slow slog through red tape, even though the city was supportive.
The fact that the company appears so committed to renewable energy suggests that the company is committed to the environment in ways that may not have a direct impact on its bottom line.

Economics for the long haul

Despite the high-tech nature of the process, the biggest innovations here might be economic. The finances of recycling are remarkably complex. Simply delivering recyclables to a sorting facility requires a transport infrastructure that completely parallels one that handles non-recyclable trash. There are typically fees involved in receiving a city's waste, whether at a recycling center or a landfill.
And then there's the value of the recycled material itself. In some cases, like aluminum, there's a huge gap in price between recycled material and freshly produced metal. But for items like plastic, recycled material is less pure than newly manufactured plastics. Since those are typically made from natural gas or petroleum derivatives, their price will depend on fossil fuel costs. "This is a really tough time for recycling, with the oil prices being very low, companies that used to buy recycled plastic are switching towards virgin plastic, because it’s currently cheaper," Quinn said. "Recycling companies are having a hard time trying to keep up with those super low prices."
All of this may mean that at any given moment, recycling can be anything from highly profitable to a struggle to cover costs. If we were to shut these facilities down during periods where they weren't profitable, however, we'd be wasting infrastructure and expertise we'd want when costs shift in the other direction.
Many cities have struggled to manage this economic complexity. New York was one of them, with Mayor Mike Bloomberg famously canceling the city's recycling program shortly after taking office.
But Quinn said that was mostly a product of the early recycling attempts, which involved a collection of small projects that were difficult to keep profitable. Bloomberg wanted something that was efficient and likely to be profitable in the long-term. "Although it was maybe not the best PR move to stop recycling, it really was done with the intention of making this a long-term, sustainable plan,” Quinn told Ars.
After Sims bought a company that was working on recycling with the city, it led to a public-private partnership between the city and Sims. The city owns the Sunset Park site and leases it to Sims. It handles the collection of recyclables and either delivers them directly to the recycling center or to a transit station where Sims transfers it to one of its barges. (Each barge can hold the equivalent of 100 trucks, so it's highly efficient transport.) The city does pay a tipping fee to get rid of the materials, but it's less than what it would pay to landfill them—plus it avoids the cost of transporting everything to the landfill.
The city even has a chance to get some of its tipping fee back. When recycled materials are sufficiently valuable, Sims shares a percentage of the profits back with the government. During periods where these materials are priced low, the company gets to keep any profits it can eke out.
The net result is that the city can benefit when recycled materials are valuable. And when raw material prices are low, it's still profitable to keep the facility operating. And its operation has value that goes beyond simple economics, Quinn argued. "Some people say, ‘If we’re not making profits, it we’re not making money out of the recycling, why are we doing it?’ But there are a lot of other reasons we’re recycling, and if right now we’re not making money, we hope that when the oil prices go back up... this will be a viable alternative."
Regardless of the price, however, Quinn told Ars that there are always buyers for the bales of recycled materials that the site produces—except for maybe those pesky plastic bags.