How to dispose of cooking oil

Olive, sesame, chilli-infused — we love to add lashings of tasty oil to our cooking equipment to help those ingredients sizzle. But what’s the best way to dispose of leftover cooking oil?

How many times can you reuse cooking oil?

Falafel frying in oil

Waste not want not — if you’re making a dish that requires a lot of oil, like pakoras or doughnuts, chances are you’ll have oil left over. Often, this excess oil can be safely reused. The question is: how many times?

Well, there’s no hard and fast rule. It depends on the oil type and how well you treat it. It’s important to make sure you don’t burn the oil the first time around, or it’ll impair the flavour of your next recipe.

Oil with a high smoking point, like extra-virgin olive or sunflower oil, can generally be used about five or six times. Once your first dish is done, leave the oil to cool, strain it through a sieve, and store it in a sealed container to use again. 

Keep an eye on it and make a judgement call. If your oil darkens, starts to smell, or has a lot of sediment, it’s probably best to throw it away.

It’s also worth noting that oil will take on the flavour of whatever you fry in it. So unless you want garlicky pancakes or fish-flavoured fried banana, you may wish to keep separate oils for different types of cuisine.

What can you do with used cooking oil?

Once you’ve cooked your meal, the logical thing to do with leftover cooking oil is to throw it away. But did you know that used cooking oil can actually come in handy around the house?

Get your tables and chairs gleaming by mixing equal parts vinegar and used olive oil. It makes a fantastic wood polish! Apply liberally, then buff away with a microfibre cloth.

Used cooking oil makes an excellent lock lubricant, too. If your key tends to stick in the door, add a little oil of any kind to loosen it. 

On a larger scale, vegetable oil can be used as a renewable energy source. ‘Biodiesel’ is becoming an increasingly popular alternative to fossil fuels, and there are a number of power plants that recover used cooking oil to produce electricity. You can check with your local recycling centre to see if they accept cooking oil to transport to a biodiesel plant.

Can I put cooking oil down the sink?

kitchen sink with water coming out of the tap

Pouring oil down the sink might seem like an easy option. Unfortunately, even the runniest oil eventually hardens and can leave a horrible build-up in your pipes. Cooking oil build-ups are a common cause of poor drainage and an unpleasant pong. 


The problem doesn’t just stop at your sink, either. When oil solidifies farther down, it can cause huge foul-smelling ‘fatbergs’. These enormous collections of oil and debris create sewage blockages that affect whole neighbourhoods. 

Any oil that does make it through the sewer systems can reduce the amount of oxygen in the water and harm wildlife.

It might be tempting to help cooking oil on its way with a chaser of boiling water. However, while this might temporarily clear any oil in your kitchen pipes, it’ll quickly cool and solidify farther down the system.

Can you put cooking oil down the toilet?

Putting used cooking oil down the toilet unfortunately has the same effect as pouring it down the sink. Once flushed, the oil will travel the same route, down the pipes and into the sewers, adding to those troublesome fatbergs. 

To avoid your bathroom becoming a plumber’s nightmare, it’s safer to collect your cooking oil in a container and either reuse it, recycle it, or bin it.

Can you put cooking oil in the compost?

A few types of vegetable oils can be a beneficial addition to your home compost pile. 

Worms love rapeseed oil, sunflower oil, corn oil or olive oil, but be careful to only add very small amounts. Too much can attract rodents and create a water-resistant barrier that blocks drainage and slows down the composting process.

It’s also important to only put vegetable oils in the compost. Animal-based products, like lard and tallow, will attract rats and other animals. They can also cause harmful bacteria and pathogens to develop. If you put vegetable oil in the compost bin, make sure it hasn’t come into contact with any meat or fish first.  

How to dispose of used cooking oil at home

When you’re looking at how to dispose of cooking oil, first consider what type of product you’re using. Is it the kind of oil that stays liquid at low temperatures, like olive oil? Or are you using an ingredient like coconut oil, which solidifies when cool?

coconut oil is easier to dispose of because it goes hard when cool

If you’re cooking with an oil that hardens at room temperature, or animal fat such as butter or lard, collect the leftovers in a jar or container and leave them to cool. Once they’ve set, you can scoop them out and pop them in the bin.

Oils that remain liquid at lower temperatures can be a bit trickier to get rid of. Pouring them straight in the bin can get messy — especially if the oil is still hot and melts through the bin bag!

Your best option is to wait for the leftover oil to cool, then collect it in a tub. Many recycling centres offer oil disposal, and you can call your local one to double-check. To save lots of trips, you can collect excess cooking oil in a larger container until it’s full, then take it to be recycled all at once. 

To remove any remaining oil residue on your cooking equipment, you can blot your pans with kitchen paper, then throw the paper away.

If you’re looking to reduce your oil use and avoid the problem of disposing of it altogether, try looking for high-quality non-stick pans, like the Zyliss Ultimate range. The innovative non-stick coating is so effective you don’t need oil or butter. 


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