This story was first published on December 27, 2021. It was republished on October 8. 

Whether it’s for saving space in your recycling bin or wanting the satisfaction of something being crushed under your feet — it’s time to squash our can-crushing habit.

Why? Well, it turns out, it’s a lot harder for aluminium drinking cans to be recycled if they are flat. 

When we throw things in our recycling bins, the first thing that needs to happen at the recycling plant is for them to be sorted. 

Wellington City Council’s waste minimisation manager, Jenny Elliot, says the machinery at these facilities separate 2D objects, like paper and cardboard, from 3D items like bottles and cans. 

The 2D items go upwards on the conveyor belt while the 3D containers drop down to a different stream for further sorting. 

“I know there is that temptation to stand on cans because it's really satisfying but if they are squashed flat like that there is a good chance they will go off to the 2D items, along with the paper and cardboard and then they contaminate that stream,” she says. 

Elliot says there are sorters who can catch and pull out plastic or cans from 2D streams. 

“But they don't necessarily have time to make sure that they then go nicely into another recycling stream, so there is a good chance they end up in landfill.

“Sorters will do their best to keep it separate but it happens quickly and there is so much to get through.”

Recycling streams need to be really clean and have minimal contamination so they can be recycled and that’s why people need to wash out any food or drink that is in recyclable containers before it is thrown away, Elliot says. 

“Our recycling plant, where the wider Wellington region’s recycling goes, processes about 135 tonnes of recycling daily. But every day about eight tonnes go off to landfill because it's contaminated.”

That is the weight of five average-sized cars going to landfill every day. And that’s only Wellington. 

“We will see up to 47,500 cans go through there a day. Most of them will be recycled but where there are problems, they will go to landfill,” Elliot says. 

“It’s a common issue our teams will see every day.”

You may have seen those huge bins of squashed cans outside schools or churches being collected.

Because these cans are already sorted, Elliot says them being squashed isn’t an issue.

“It’s when the recycling needs to be sorted is where the issue comes up.

“At the end of the day, being squashed doesn’t affect the way the can is recycled. The cans all end up going to a scrap metal recycler overseas.”

“But not squashing cans allows them the best chance to be sorted correctly so they don’t end up in landfill,” she says.

If the can has a dent in it, Elliot says it will most likely still be recognised as 3D but it is best to keep them in their original shape as much as possible.

This no squash rule also stands for things like milk bottles or yoghurt containers. 

It’s also important to remember that plastic and metal lids on bottles are not recyclable through the kerbside recycling system. 

In fact, anything smaller than a yoghurt pottle is too small to go through the sorting process. 

But don’t worry, the Sustainability Trust has a free collection point for metal bottle caps (like the ones you find on wine bottles), plastic lids and lids for glass jars. 

If you are tossing up between beverages in cans or glass this summer, which one is better for recycling? 

“It's a difficult one,” she says. “There are lots of different ways you can look at it which would probably give you different answers.”

On the one hand, cans are lighter so if your beverage is shipped from somewhere far, lighter packaging means less gas and less CO2 are being produced. 

But on the other hand, glass can be recycled right here in New Zealand. Cans have to be shipped overseas to be recycled.

“I think ideally, we would be using glass and the glass would then be cleaned out, sterilised and reused so it wouldn’t have to go through the recycling process at all. That's where I'd like us to get back to.”

“But while there are some places where you can take your own vessel to be refilled, we are not at the stage where that is practical for everyone,” she says.

“So for now, I’d probably choose local drinks in glass bottles.”

Top image: Pile of crushed drink cans. Photo: Ryan McVay/Getty Images

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