A new life for used cooking oil

One of the biggest headaches in any kitchen is used cooking oil. After being used to fry food, what do you do with the oil?

Should we keep it or throw it down the drain? Can it be reused? The uncertainty of what to do with it can even make you lose your appetite for that falafel you just cooked. If you see yourself in this picture, know that your used cooking oil can be useful – and helpful for the environment.

We are talking about biodiesel, which may represent a reduction of up to 80% in carbon emissions compared to conventional diesel. Biodiesel is a fuel of non-fossil biological origin, renewable and biodegradable.

The problem: disposing of cooking oil without criteria

Did you know that, according to EU estimations, every year over six million tonnes of used cooking oil could be collected for recycling in Europe? This is almost two and a half times more than the current collected amount. This means that there are nearly 3.6 million tonnes of cooking oil not being properly taken care of after serving its purpose in kitchens all over Europe. And much of these million tonnes of oil may end up in sewage systems.

Just 1 litre of used cooking oil can pollute up to 1 million litres of water – almost half of the water in an Olympic swimming pool. At the same time, it can also cause problems in wastewater treatment plans, since the accumulation of grease can block the cleaning filters.

When discarded to the common trash, the oil is mostly sent to landfills, where it will degrade in the absence of oxygen. This process of biodegradation is, however, responsible for the emission of greenhouse gases such as methane. It is indeed a better solution than literally throwing it down the drain, but there are other, and better, options at play here.

For each tonne of used cooking oil sent to recycling instead of to a landfill, it is possible to avoid the emission of around 14 tonnes of greenhouse gases.

How to store and recycle used cooking oil?

After using oil to cook, let it cool completely. Pour it into an empty plastic bottle and store it tightly closed in a cool, dry place until full. Once completely full, put this oily bottle in the appropriate bin. This depends on which country you live in and what garbage collection facilities are there.

For instance, in Portugal, there are a type of recycling bins specially designed to collect used cooking oil. These are called Oleões from the Portuguese word for oil – óleo. You can find them in more than 250 Pingo Doce stores all over the country, and so you can dispose of your used oil with a clear conscience.

Between 2009 and 2020, more than one million litres of used cooking oil were collected in Pingo Doce's "Oleões".

In such bins you must only discard of used cooking oils, be it from deep-frying, general cooking, olive oil or tinned foods like sardines and tuna. Engine lubricant oils must never be deposited in these bins.

Do not use glass bottles or jars to store the oil. Glass has a higher risk of breaking either at the collection centre or during transportation to and from. Instead, use that single-use plastic bottle you bought when you forgot your reusable one, or an empty juice bottle.

Used cooking oils can be used to make soap and biodiesel.

What happens after the recycling bin?

If there is a possibility to separate them by type, used cooking oils can be used to make soap. In case separation by type is not possible, these oils can become biodiesel.

Each 1,000 litres of used cooking oil yield around 950 litres of biodiesel. To produce biodiesel, several methods are used. The most common method includes submitting the oil to a chemical process known as transesterification. The final product is biodiesel and glycerine as a by-product. While biodiesel is used as fuel for cars, buses, trucks, coaches and even aeroplanes, glycerine may be used for soap production. Circular economy, indeed.

The cooking oils used in Pingo Doce’s kitchens, as well as the oil used for grilling in-store, are properly forwarded to valorisation facilities. Part of it becomes biofuel, and the remainder becomes fertiliser for agriculture.

In 2020, more than 620 tonnes of residues deposited by customers at Pingo Doce and Recheio (Portugal), Biedronka (Poland), and Ara (Colombia) stores, were sent to recycling at valorisation facilities. These residues included more than 100 tonnes of used cooking oils.