The Plant Industry's Dark Secret: Black Plastic

That black plastic plant pot you threw in the recycling bin likely ended up in a landfill. Here’s why.

You just bought a house plant for your apartment. You feel great: Your place looks nicer, and you’ve contributed to one of the greenest industries in the world. Or have you?

Under that beautiful Monstera plant hides a dark secret: The black plastic pot you will throw in the recycling bin after you’ve repotted the plant might not be recycled.

“The problem is that optical readers at recycling facilities cannot detect black,” said Marie Chieppo, a researcher, landscape designer and horticulturist.In 2020, Chieppo looked into the recyclability of plastic plant pots for the Association of Professional Landscape Designers. Through her research, Chieppo found that “most optical readers used at recycling facilities cannot identify black plastic pots.”

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That means that the scanners can usually detect things like white plastic forks, blue plastic cups and green lids and set them aside for recycling. But when it comes to black products, the scanners simply can’t see them.

“They're often thrown aside into bins and so forth, because the recycling people know that the optical reader is not going to read it. So they just toss it to the side,” Chieppo said.

Many recycling facilities use what’s called near infrared sorting systems to detect color. In the United Kingdom, an analysis of data showed zero percent of plastic that is the color carbon black is detected with that technology.

And anything that is not sorted for recycling? 

“They go to landfills,” she said.

“The color black is difficult to capture with optical sorters,” Balcones Resources, one of the companies that handles recycling for Austin, Texas, said via email. “This is why we always implement a combination of optical sorting and manual sorting (machines and people).”

Chicago has similar additional lines of “defense.”

“The material is sorted manually and mechanically using technology that distinguishes the plastic’s resin from the black conveyer belts,”  a spokesperson for the City of Chicago told LX News. 

San Francisco says it also says “advanced sorting technologies” that allow it to detect black plastic. But even then, there's another problem. The quality of the plastic.

Recology, San Francisco’s, recycling service provider, says thick black plastic pots are usually recycled at their facilities. That’s because the plastic that makes up those pots, HDPE, or high-density polyethylene is considered a high quality material.

The problem, they say, comes with thinner black plastic.

“The thinner ones are more challenging to recycle if there is no corresponding market,” a spokesperson for Recology told LX News.

It’s important to remember that recycling is a business. Someone has to buy the plastic after it’s recycled for a city as big as San Francisco to put time and resources into recycling it. And Chieppo says some black plastic — usually the thinner variety — is considered “cheap plastic,” because of its composition. 

Black plastic is usually made up of different types of resins, or types of plastic. 

“You cannot recycle a product that contains different resins. You just—you can't,” Chieppo said.

That’s because different types of plastic melt at different temperatures. Because of that, facilities risk pots not melting completely and contaminating entire loads of waste.

So why not just use pots that are not black? Chieppo’s research found that colored pots aren’t that much better. For one, pots don’t always arrive clean enough to be recycled. You also still run into the issue of different types of resin, which makes them difficult to recycle.

As a result, many plastic pots, regardless of color, are simply sent off to landfills. There is no recent data, but a 2015 Nursery Management article said 98 percent of plastic containers for plants ended up in landfills.

“That in and of itself has created a huge nightmare in terms of the recyclability of these parts,” said Chieppo.

So what is the solution?

“Fiber-based pods are coming on the market,” Chieppo said. “I'm talking to manufacturers. I'm talking to producers. Bioplastic pots are making their way onto the market.”

These alternatives are made from biodegradable alternatives like sawdust, vegetable oil and paper. But Chieppo says they haven’t reached the level of mass production that black plastic has — and they are also more expensive.

The good news is I think people are becoming much more aware of the environment and climate change and the emissions that are being used  for a number of reasons,” said Chieppo. “And [research] has shown that consumers are willing to pay a little bit more.

Some plant shops are piloting makeshift solutions to divert black plastic pots from landfills.

“We try to reuse plastic parts as much as possible,” said Danae Horst, the founder of Folia Collective, a plant shop in Los Angeles.

We have a bin here in the shop where customers can come and either leave pots that they are getting rid of and don't need anymore, or they can come and take them if they're ready to pot up a bunch of new things,” Horts said. “So we're really trying to keep the pots themselves out of landfills at all costs.”

But Horst says the biggest hurdle is awareness. 

“There really is a big knowledge gap when it comes to recycling,” said Horst. “Especially with things like plant pots where customers assume that because they're plastic they can be recycled.”

Chieppo is hopeful manufacturers will soon start mass-producing non-plastic alternatives that are just as strong as plastic. But in the meantime, she wants consumers to “hold on a little bit longer.”

“Find different purposes for them. And the best scenario would be if these [plant] nurseries took them back.”

However, if you cannot reuse them, recycling centers would still prefer you throw the pots in the recycling bin as opposed to the general trash bin.

“Recycling markets are always changing,” Recology said. “It’s still best to put all of the rigid plastic material into the blue bin and let the sorting machines do the rest of the work. We want to remind consumers that all of the plastic material must be clean, free of dirt and residue, in order to maximize recycling value.”

This story is part of Connect the Dots, our series that shows how different aspects of our lives are connected to each other. Watch the video above to see what ties house plants, street vending and brunch together.