Until recently I used to sneak used pizza boxes into the recycling bin, even though I knew you're not meant to.
"What harm can it really do?" I'd think.
Well, it turns out there's a perfectly good reason why pizza boxes can't be recycled.
The Garbage Queen on TikTok, who's a scientist and works in recycling, explains exactly why gross, greasy and oily pizza boxes can't be recycled.
Pizza boxes are made of corrugated cardboard and, when it gets recycled, it's melted down into pulp. Oil and grease can't be removed from the cardboard during the pulping process. If there's too much oil, the pulp has to be sent to landfill, so your soiled pizza box could be responsible for even more waste.
So what can you do with a greasy pizza box?
If some of the box doesn't have any oil on it – for example the lid – then that can be torn off to go into the recycling bin. Then any part of it that has grease stains on it can go into a compost bin. If you have a green waste bin, the oily box can go in there too.
What else can't be recycled?
As well as greasy pizza boxes, there are plenty of other items that are often put in the recycling that mess up the whole system.
Here are the most common offenders:
1. Plastic bags
This can't be repeated enough: plastic bags and soft plastics, such a pasta packaging, bread bags and biscuit wrappers, cannot be recycled in your kerbside recycling bins.
There's also no point in putting your recycling in a plastic bag and putting it in the recycling bin – this could potentially contaminate the contents of the entire bin.
The reason they can't be recycled is because they can easily be caught in the recycling plant conveyor belts and have been known to shut down the entire system.
This doesn't mean they need to go into landfill though – oh, no! – instead you can take them to soft plastic collection bins and they will be recycled.
2. Takeaway coffee cups
Most single-use coffee cups have a plastic lining made of polyethylene which makes them waterproof. So even though the cups also have a paper layer, they can't be recycled because the materials can't be separated. Crazy when you consider New Zealanders throw away 295 million coffee cups a year.
Chucking a coffee cup in the recycling will contaminate the bin and may mean other recyclable items are sent to landfill.
Put your single-use coffee cup in the general bin or swerve the single-use cup altogether and buy a KeepCup or similar cup.
Some cafes stopped taking reusable cups due to Covid but in June, 119 scientists from 18 countries signed a statement to say that reusables are safe.
3. Toothbrushes and toothpaste tubes
Because they're made of multiple layers of different plastics fused together, toothbrushes and toothpaste tubes can't go in the general recycling. There is a great solution though.
The company TerraCycle has a free Oral Care Recycling Programme which means you can put your old toothbrushes and used toothpaste tubes in an envelope and attach a printable barcode they will send to you to post them out for free. They will then be melted down and turned into new products such as park benches and playgrounds.
• Riah Matthews is the commissioning editor for news.com.au