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What is the best way to dispose of cooking oil?

By: Jon Greaves on Dec 21, 2022

We've all been there. You have spent ages cooking a meal and just need to pour away that leftover fat so you can serve the dish. So you pour it down the sink; then rinse your greasy pots, pans, and plates and forget about it.

This might seem innocuous enough, but millions of people over the country are doing the same with oil, butter, and cooking fats. Every year, British households pour 18 million litres of cooking fats down their sinks—enough to fill seven Olympic-sized swimming pools.

Who are the country’s worst offenders?

A study conducted in 2016 looked at the percentage of people in different areas of the country who admitted to pouring fats and oils down the sink.

  1. North East (62%)
  2. South East (60%)
  3. South West (58%)
  4. London (56%)
  5. North West (55%)

What’s the problem with pouring fats and oils down the sink?

When poured down the sink, fats, oils, and greases cause plumbing, environmental, and economic problems. 

Clogging: Fats and oils can solidify and stick to the sides of pipes, eventually forming a clog that can block water from flowing. This can lead to slow-moving or completely blocked drains; eventually, the drains will have to be unclogged, or the pipes replaced. 

Burning pipes: Pouring hot oil down a sink can burn plastic piping by eroding the inside. 

Odours: Fats and oils decompose over time and produce unpleasant odours in your plumbing system.

Environmental issues: When fats and oils enter a building’s wastewater treatment system, they can disrupt the system and cause problems in the treatment process. If they enter bodies of water, they harm plants and animals.

Also, blockages arise when fats and oils combine with plastic wipes and other items that are flushed down the toilet (that shouldn't be). These can happen in a domestic sewage treatment plant, a building's local wastewater treatment plant, and the public sewer network. Overflowing sewers cause severe damage to the environment and are a grave threat to human health. 

Economic issues: Not correctly disposing of fats and oils costs home and business owners a hefty sum on plumbing repairs—plumbers can charge over £60 an hour. And local councils have to spend tens of thousands of pounds a year. Businesses operating in the UK's food industry are legally required to dispose of cooking oils and fats correctly. Non-compliance can result in huge fines and the forced closure of their premises—as stipulated in the Food Safety Act (FSA) 1990. 

When does cooking oil cause fatbergs?

Perhaps you remember the largest ever fatberg discovered in Whitechapel, London, in 2017, measuring 250 metres long. A fatberg is a vast buildup of oil, fat, grease, and sanitary products—all of which have been incorrectly disposed of down sinks and toilets.

These materials accumulate, congeal, and then become very hard. Fatbergs block public drains, which can spill wastewater into gardens and houses. 

In the UK, it costs over £100 million annually to remove fatbergs and make sewers safe. The fatberg first needs to be broken un with a high-pressure water jet. It is then extracted either manually or using a combination tanker. Finally, the pieces are transported to a specialist facility where they are either disposed of correctly or recycled, if possible. 

What is the best way to dispose of cooking oil?

All food waste, including cooking oils and fats, should be placed in a sealed container and then put into the general waste. There are several different ways of disposing of cooking oil and fat.

1. Allow the oil to cool: It is essential to let the oil cool before disposing of it. Hot oil can be a fire hazard, and it can also cause your waste container to break or melt.

2. Remember, don't pour the oil down the drain: Pouring grease down the drain can cause it to clog pipes and cause damage to the sewage system. It can also harm wildlife if it makes its way into rivers or streams.

3. For small amounts of oil: When cool, small amounts of oil, from a frying pan, for example, can be spooned directly into your general waste once it cools. 

4. Remove as much oil as possible: Remove oil from every greasy item, not just big pans, before washing them or putting them in the dishwasher, as even a small amount of oil can cause problems. Soak up any oil or grease on the bottom of plates and pans with a paper towel before throwing it away in the kitchen bin.

5. For larger amounts of oil: Pour the oil into a sealable container, such as an old plastic takeaway container, bottle, or jar—anything that has a tight lid. This will prevent the oil from spilling and make it easier to dispose of. It's a good idea to leave a container next to the sink to use several times and then dispose of it when it is full. 

6. Dispose of the oil correctly: Many places around the UK have access to a food waste recycling service that deals with the disposal of cooking oil. This service uses specialist equipment to recycle the oil into biodiesel or other products. Moreover, some supermarkets collect used cooking oil. However, if you do not have this service in your area, you should dispose of the oil in your general waste bin in a sealed container.

Following these tips can help contribute to positive water management for the environment and prevent costly damage to your pipes and sewage system.

Can I reuse cooking oil?

If you have a large amount of oil, it is still in good condition, and it has not been contaminated, you may be able to reuse it for cooking. 

  • Strain the oil to remove any food particles using a sieve
  • Store it in a clean, airtight container for reuse. Oil can generally be reused several times, but dispose of it if it becomes dark or smells bad.

A common misconception about cooking oil disposal

It's a common misconception that you can wash hot oil and grease away with soap and warm water. Water and oil cannot mix as water is denser than oil; this means oil still remains in the pipes causing damage. 

In fact, 'washing' oil this way will likely exacerbate the problem. Putting more washing-up liquid down the sink causes the pipes to harden, and the soap sticks to other debris, adding to the problem.  


Incorrectly disposing of cooking fat and oil can cause severe damage to our homes, wastewater plants, sewers, and rivers. When poured down the drain, grease solidifies and builds up inside pipes, creating challenging and costly blockages.

If we put fats and oils in the bin rather than down the sink, we will save ourselves money and hassle, and we protect our environment. 

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Topics: Wastewater Treatment

Jon Greaves

Written by Jon Greaves

Jon has progressively worked through operational roles, account management, technical management, and senior management roles over the last 16 years within one of the group companies before moving into the role of Water and Air Managing Director. Jon has experience across multiple sectors of water and air compliance, including district energy networks; data centres; healthcare; food and beverage and facilities management. Jon acted as a corresponding steering committee member on CIBSE CP1 – Heat Networks Code of Practice for the UK released in 2020.

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