Remember those freaky ‘tar balls’ that washed up on beaches up and down Sydney’s coastline last month? As it turns out, they were not made of tar after all. An analysis by scientists from the University of NSW has found that these icky black blobs were made up of waste generated by humans. We won’t ruin your lunch by giving you all the gory details, but one of the key ingredients identified was cooking oil. 

You’ve no doubt heard of the ‘fatbergs’ that have been found lurking in our sewer systems. These are caused by people pouring oil down the sink instead of disposing of it in a more *cough* responsible manner. These black balls are kind of the same thing – a bunch of waste all glued together by fats and oils. 

While cooking oils and the oil from your lunchtime can of tuna might be liquid when you sneakily drain it down the plughole, they harden as they cool, wreaking havoc as they make their way through our wastewater systems. Even if you think you’re being clever by breaking down the oil with dishwashing liquid, the oil will still solidify when it cools, so you’re back in fatberg territory either way. 

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What is the right way to dispose of cooking oil?

Small amounts of oil can be drained into a sealable container (like an old jar or bottle) and placed in your garbage bin. A funnel is handy for this. Just make sure the oil has cooled down before you do this. Once you’ve drained your pan, wipe it out with a paper towel and pop that in the bin, too. If you’re just using a small amount of oil to cook, it’s still a good idea to wipe out your pan with paper towel after you’ve finished cooking. 

If your council provides a FOGO (food organics and garden organics) bin service, you can also dispose of small amounts of oil in this, but it will need to be absorbed by paper towels or newspaper, or mixed in with other food waste first. You can also add small amounts to your home compost bin, but if you add too much, this will slow down the composting process. 

For large amounts of oil, pour it into a sealable container, and drop it off at a recycling service that accepts cooking oil. You can find one near you here. 

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Can you reuse cooking oil?

For sure! If you’re using a large amount of oil to deep-fry, you can reuse your oil. Once you’ve finished your fry-up, strain the oil into a container (through cheesecloth placed in a fine strainer is best). The more food particles that are left in the oil, the quicker it will become rancid. 

A clever tip is to add a label that tells you what the oil was used for, so you won’t accidentally ruin your next recipe (for example, if you used it to deep-fry fish, you won’t want to reuse the oil to make a batch of doughnuts). Add the date of when you used it, and the number of times you’ve used it, and then store in a cool, dark place. 

There’s no definitive rule on how many times you can reuse your oil, because it depends on what you’re using it for. But if your oil starts to look foamy on the top, smells funny or looks dirty or cloudy, it’s time to dispose of it. Properly.

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