Pescaíto, squid, fritters, donuts, croquettes, churros. Even milk likes fried in Spain. Oil is part of our culture and is present in the kitchen of our day to day. In Spanish homes, almost 12 liters of oil per person were consumed in 2021, according to data from the Ministry of Agriculture, Fisheries and Food. If we add its industrial and restaurant use to domestic consumption, in Spain some 150 million liters of used cooking oil are generated each year.
But... Once used and reused, oil becomes waste. And then what do we do with it? Where is it going to stop? Oil is a 100% usable waste with a rich composition. Properly recycled and treated, it can have different lives in various sectors such as mobility, construction, healthcare or agriculture. One of its most promising uses is the production of renewable fuels, a complementary solution to achieve decarbonization that favors the circular economy and helps reduce greenhouse gas emissions. "Used oil is waste that must be disposed of and an excellent opportunity is to use it as a raw material to manufacture advanced biofuels," says Rafael Roldán, a researcher at the Repsol Technology Lab. "With its use we can generate this type of renewable fuel which is zero net emissions and can be used in current car, truck, plane or boat engines”, says the expert.
Currently, the collection of cooking oil already used in the Spanish hospitality sector is high. According to calculations by the National Association of Edible Oil and Fat Waste and By-Product Managers (Geregras), the Horeca sector (hotels, restaurants and cafeterias) recovers 72% of the oil it uses in its kitchens. In Spanish homes the figure does not reach 5%, which means that there is still a lot of pedagogy to be done. But the recycling figure will increase from 2025, since Law 7/2022 on waste and contaminated soils establishes the obligation to segregately collect used cooking oil from homes as of December 31, 2024 (collection obligations and management are municipal competence).
This boost to the collection of used oil -also called UCO (Used Cooking Oil)- to manufacture biofuels with a low carbon footprint has already given promising results in pioneering projects in Spain. In Cartagena (Murcia), Repsol is advancing in the construction of the first advanced biofuels plant in Spain, which will produce fuel from waste from the agri-food industry, used cooking oils, among others.
Used household oil must be recycled by taking it to a collection point. Before taking it, wait for it to cool down and pack it. And remember not to mix leftover cooking oil with motor oils or industrial greases.
It is clear that used oil can be 'liquid gold' and that its recycling fulfills two functions: preserving the environment and favoring the circular economy. After being collected, how is it turned into useful products?
Raw materials for the production of new products
Much of the collected oil is regenerated into new lubricants. This is done in treatment plants where, in addition to water, additives, heavy metals and other sediments are removed. As a result of the entire process, a refined oil is obtained that is used in the aforementioned manufacture of high-quality lubricants, or an asphalt product for the manufacture of waterproofing fabrics and roads, for example.
energy resource
Another option is to chemically modify the oil through a transesterification process. This is done in industrial plants, where advanced biofuels are obtained –such as biodiesel, biojet, bionaphtha and biopropane– which are used in planes, ships, trucks or cars.
Companies, municipalities, waste managers and, of course, the citizen, join efforts to give new life to used oil. Recycling the oil that we use daily is within everyone's reach and it only means a change in habit that can be key for the future.
