The best way to dispose of cooking oil is to collect it in a suitable, sealable container that’s large enough for storing 4 to 5 gallons of liquid oil. When the container is nearly full, take it to your local recycling centre. Cooking oils and fats that harden can be allowed to solidify and binned in small quantities.
Also: Why you shouldn’t pour cooking oil down the sink
How does cooking oil affect the environment?
How businesses should dispose of cooking oil
Things you can do with used cooking oil in the home
Make soap from used cooking oil
If you don’t have large containers, you can store cooking oil in smaller plastic bottles, which have, for example, contained drinks. It may not be so easy to fill a small plastic bottle but as long as the bottles can be sealed tight it’s good enough for storing before taking it to the recycle centre.
Put safety first when disposing of cooking oil
Cooking is all about getting things hot. Where there is heat there is danger and hot cooking oil in the kitchen can be one of the biggest dangers that there is. When we cook anything in a pan the oil is likely to reach a temperature of around 120°C. When we use cooking oil to bake in an oven, we can expect temperatures in excess of 180°C.
The biggest risk of all has to be when we have large volumes of cooking oil in one vessel, for example a deep fryer. To get cooking oil hot enough for us in a deep fryer, the temperature needs to be between 160 and 180°C.
Before we think about how to dispose of cooking oil, we need to be aware of these high temperatures and the potential hazards.
The simplest and safest approach is to allow hot cooking oil to cool down before we set about disposing of it.
You need to know about how to dispose of cooking oil and the ways of doing so, even if it’s just a small amount that needs to be disposed of. But before we look into those methods, we need to understand why we need to take the issue of cooking oil disposal seriously and why a small amount of effort from each of us can make a big difference.
The importance of why & how to dispose of cooking oil
Why you shouldn’t pour cooking oil down the sink
The first advice that you will get when you ask about how to dispose of cooking oil will be how not to dispose of it. It cannot be repeated often enough that we must not dispose of cooking oil or fat by pouring it down the plughole.
While this may appear to be a convenient way of removing cooking oil from your life, the small amount that you may be throwing away will be a contribution which, when added to everybody else’s contributions, will cause a sizeable problem in the drains for somebody else to deal with.
It’s easy enough to think that your small amount of cooking oil can disappear out of sight into the underworld of the drains and that it won’t make any difference. It isn’t until it’s fully explained what happens when cooking oil and other liquefied fats find their way into the sewage drains that the horror of it comes to light.
Warm cooking oil will run easily to find its way down into the drains but when it gets there it will quickly cool down and solidify. When this happens it will stick to the walls of the drains and will gradually build up. Added to this there is often the complication of other materials that have been flushed into the sewage pipes, for example wet wipes and a whole variety of household materials.
The cooking fat that finds its way into the drains will become a glue that will stick everything else together and allow a mass of material to build up in one place. This mass of material is affectionately known as a ‘fatberg’.
Where there are large drains in the sewage system, ‘fatbergs’, generated from disposed-of cooking oil, will grow to a size that the space will allow. There have been reports of ‘fatbergs’ that have been allowed to grow to the size of a bus and in some cases even bigger.
The Thames Water Authority, London UK, is believed to spend £18 million a year on the removal of ‘fatbergs’ from the sewers. Understandably, this draws the comment that this is money that’s going down the drain just like the cooking oil.
Boiling water won’t clear the drains
Some people have the idea that if you mix cooking oil with boiling water and detergent that this mixture can safely go down the drains. Up to a point, this will work but it shouldn’t be advised by anyone. Detergent will break down the structure of the oil to an extent but it would take an excessive amount of detergent to break down cooking oil enough to avoid blocking the drains.
There is also the issue of sending detergent down the sink and into the drains. Detergent can be described as an anionic biodegradable surface-active agent which means that it will break down. But large concentrations of it in one place can cause a short term pollution complication until it fully breaks down, so, this is better avoided.
As for the use of boiling water going down the drains, it may clear some of the cooking oil residue that collects near the outlet of the sink but will do nothing any further than that. Hot water will cool very quickly as it flows along underground pipes.
How does cooking oil affect the environment?
In small quantities, spread over a large area, it could be said that cooking oil would have little or no impact on the environment. All oils, including cooking oil, are actually an energy food source to certain forms of life, usually microscopic life-forms.
Cooking oil will therefore become digested and broken down in the environment where the conditions are favourable for this to happen.
The problems begin when a large quantity of cooking oil is deposited in one place thus overloading the environment’s capacity to break it down by natural means. If a large measure of cooking oil finds its way into a water course, it would then become a pollutant.
This doesn’t mean that cooking oil, itself, is toxic but the microscope life-forms that feed on it will multiply to such an extent that they will remove much of the oxygen in the water of a river if the river becomes contaminated. This is when you may see evidence of reduced oxygen levels in the form of dead fish. This will, however, be temporary.
In a case where a waterway or area of land becomes overloaded with a deposit of cooking oil, there will be consequences to the immediate environment but it will not be anything long-term. Cooking oil is, essentially, organic in the true sense of the word, being carbon-based and once living.
Over a relatively short passage of time cooking oil will break down by natural means and leave no long-term adverse reaction.
Any cooking oil that finds its way into the sewage drains has to be broken down, along with everything else. The remaining liquid that emerges from water treatment plants will be free of cooking oil and will cause no harm to the environment. By reducing or avoiding the release of cooking oil into drains, we can all play a part in helping to reduce the load intensity on the water-treatment works.
How businesses should dispose of cooking oil
Businesses in the food-cooking industry are likely to be using larger quantities of cooking oil compared to domestic situations. A business has a legal obligation to dispose of cooking oil in a manner that doesn’t pollute or adversely impinge on others. The disposal of cooking oil that’s used by business for industrial cooking processes is regulated and there are fines waiting for operators who fail to comply.
The situation is made easy for any business that needs to dispose of cooking oil. There is a new industry emerging that will take such waste and process it into biofuels.
Dispose of cooking oil legally
Ensure that those who collect your cooking oil for disposal are operating legally. Before you release it to be disposed of, check that they are registered with the Environment Agency for your district. Beware of ‘cowboys’ who turn up and offer the service of cooking oil disposal. They may try to charge you for collecting it and then take it out into the countryside where they will just empty it into an open field.
A genuine, legally registered cooking oil collection service will collect it and pay you for it. They will recycle your used cooking oil into biofuels. Domestic quantities of cooking oil tend to be lower but there are disposal firms that will collect this for free, depending on the quantity involved.
There will be a minimum quantity level for disposal of used cooking oil as this service is aimed at the commercial food industry.
Storing of used cooking oil for business
There are legal requirements of food industry businesses to store cooking oils in a safe and secure manner while waiting for a registered waste disposal company to collect it. Used cooking oils must be stored in designated storage tanks with no risk of leaks. If any oil does leak, there is a risk of drain-pollution, smells and general hygiene issues which will, likely, contravene standards.
Always use a registered waste carrier
It’s the responsibility of any business to dispose of cooking oil waste by legal methods. Only Environment Agency Registered companies that offer the service of disposing of cooking oil, can be used.
When a registered waste-disposal company collects cooking oil they are legally required to provide a ‘ waste transfer document’ for the tracking and tracing of the cooking oil consignment. Business owners are also required, by law, to keep records of all the disposed-of cooking oil for at least 6 years.
What happens to waste cooking oil?
Historically companies found it convenient to dispose of cooking oil by sending it to pig farms where it would make up part of the pig-swill content, used for feeding pigs.
Things have moved on. Cooking oil now has a value that makes it worth collecting to be refined into modern biofuels. The process of refining used cooking oils into ‘green’ or biodiesel has become big business. This makes it worthwhile for those who generate moderate amounts of used cooking oil. It can be sold to processors, thus reducing the risk of pollution or causing blockages to drains.
The ecology figures look good as well. In the UK the Renewable Energy Association has stated that converting cooking oils to biodiesel can achieve a carbon reduction of 88% over fossil-fuel diesel. It’s also been noted that the recovery of used cooking oils triumphs over the practice of crop-based fuels. Crop-based fuels secure a carbon reduction of 50-60% over fossil fuels.
The technology of refining cooking oil into biofuels has led to a demand for it, with cars, lorries and buses being able to run on it.
You may not need to dispose of cooking oil
Things you can do with used cooking oil in the home
Old cooking oil is being used in many ways in the home and garden. If you can make use of it, yourself, you may not need to dispose of cooking oil at all. Here’s what some people have some success with:
1. Garden tools
Metal surfaces tend to rust and wooden handles tend to deteriorate when left in storage. Take a cloth, soak it in old cooking oil and wipe a thin layer onto the entire surface of all your garden tools. Take a look around and see what other items are exposed to the elements. Anything that’s metal or wood will benefit from a wipe over of cooking oil.
2. Removing paint from hands
Some people have success when using old cooking oil to get paint off their hands. It seems to work if you rub some cooking oil over your hands, and hair, if necessary, then leave it for a few minutes. Then rinse it off and the paint should come away. I haven’t tried this but I suspect you will need to follow on with soap.
3.Use old cooking oil as a weed killer
Here’s an eco-friendly way of tackling weeds. Pour some old cooking oil into one of those hand sprayers and spray over specific weeds that you want to remove. For best results you need to coat the whole weed-plant with a layer of cooking oil. This is enough to stop the plant from functioning.
4. Cooking oil as a make-up remover.
This appears to work for some. Cooking oil is known to remove some of the toughest make-up. Some have experimented and found some success with cooking oil but gone further and fared better when using coconut oil or almond oil.
5. Cooking oil as a hair conditioner.
No. You wouldn’t want your hair smelling of bacon fat or fish and chips. There are some oils that can be used with good effect. Olive oil, coconut oil and orange oil appear to be effective for some. Apply the oil of your choice then cover your head with a towel or shower-cap. You need to leave it undisturbed for an hour or two; some people leave it overnight. It will take a lot of rinsing, then wash with a shampoo.
6. Can you dispose of cooking oil in the compost bin?
This can work. I do it all the time when feeding the Rolypig composter. But you need to know the limits. A small quantity of cooking oil added regularly to a compost bin can be digested very effectively. A compost bin is no place for gallons or litres of cooking oil being added all-in-one-go.
The best way to dispose of cooking oil in compost is to absorb it onto some newspaper. This way you will have it contained in the compost; it won’t drain away. The microbes in the compost will get to work on it and break down both the paper and the cooking oil.
Some will tell you that you mustn’t put animal fat into compost because it will attract vermin. This is true but you can negate the problem quite easily by sprinkling hydrated white lime over the oil-soaked newspaper after you’ve added it to the compost. It will help if you only add cooking oil or animal fat oil to a compost bin that has a good amount of compost in it. Don’t start by adding cooking oil from the point of having an empty bin.
More ways to dispose of cooking oil
Re use cooking oil and cook with it again
This may not seem to be hygienic to some but never forget that when we cook with cooking oils, we cook at high temperatures. The main issue with reusing used cooking oil is filtering out all the bits of food that become immersed in it from the previous cooking session.
Before thinking about reusing used cooking oil you need to know that the oil hasn’t been overheated. That is, it hasn’t been heated beyond its smoke point. If it has, then, it must be considered as partly burned.
Straining out the bits of food from the previous cook isn’t difficult. You just need a membrane material that will catch all the bits and allow the oil to pass through. For this you can use coffee filters, cheesecloth or even paper towels. Do the filtering when the cooking oil is warm. This will allow it to flow through the filter membrane faster.
How you store the filtered cooking oil is important. The fridge or freezer would be good places. Before you use it again, check that it’s good enough to use. This usually involves using your nose to tell whether it’s gone off or rancid.
Cooking oil and if you live in Scotland UK
If you are lucky enough to live in Scotland there are no less than 7 cooking oil collection banks located in ‘Sainsburys’ car parks. From there it’s taken to a recycling plant to be turned into biodiesel.’
Don’t dispose of cooking oil, turn it into soap!
Make soap from used cooking oil
Using some basic chemistry and exercising care at all times, you can actually turn cooking oil into soap that you can use. The process has to be called potentially dangerous but if you wear protective clothing and watch what you’re doing it’s possible to make a passable bar of soap rather than dispose of cooking oil.
- You will need a new pair of rubber gloves. ‘New’ because you will be sure that they have no holes.
- You must wear goggles to protect your eyes.
- Plastic apron
- You will need utensils for stirring the mixture. Use plastic or wooden utensils if possible. Metal utensils may emit hydrogen vapours.
- A plastic, glass, china, earthenware or stainless steel container to mix the ingredients. Avoid ferrous or aluminium metals.
- A mould for forming the solid soap.
The ingredients for making soap from cooking oil
- 1 litre of used but filtered cooking oil
- I litre of water (preferably distilled)
- 160g of 90%caustic soda (aka sodium hydroxide – available at a pharmacy) About caustic soda
- 30-40ml of essential oil for fragrance. (This is optional)
The stages for making soap from cooking oil
- Put on the goggles, rubber gloves and apron.
- Put the water into the mixing container
- Carefully add the caustic soda, stirring to dissolve it fully. As you do this you will note that the mixture will heat up. It will reach about 80°C. There are likely to be vapours given off at this stage which you must avoid breathing in.
- After mixing, move away from the mixture and allow it to cool to about 30°C. When cooled add the essential oil at this stage.
- Gradually add the cooking oil into the caustic soda solution. It’s important that you constantly stir the mixture as you add the cooking oil and continue to do so for 35 to 45 minutes thereafter. It’s also important to constantly stir in the same direction throughout (this will help with the structure of the finished soap).
- Keep mixing until the mixture starts to thicken (this stage is known as the ‘saponification’ process).
- Look for a texture that is stiff, almost like a runny paste. This is when you can pour the mixture into your mould or moulds.
- Allow the soap to harden and dry, this may take 4 to 5 weeks.
Things to know about caustic soda
Caustic soda or sodium hydroxide (NaOH) is available at pharmacies. It’s available in a white powder. As the name indicates, it’s caustic, meaning that it will burn your skin in its concentrated form.
Keep it out of reach of children
When having anything to do with caustic soda it’s recommended that you keep a bottle of vinegar close at hand. If, by chance, you spill some concentrated caustic soda on your skin, pouring vinegar on the area will neutralise the situation instantly. The acid of the vinegar should be enough to react with the alkaline of the caustic soda.
It’s advisable that you wear long-sleeved clothing together with the plastic apron in addition to the goggles and rubber gloves when making soap from cooking oil. Carry out the whole process in a well ventilated area as there’s likely to be vapours which mustn’t be inhaled.
Find out what else you can recycle:
How to dispose of razor blades
Image sources: pork in oil | food oil | samosa cooking | Fry potatoes | bacon | soap bars