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Olives turn into heat and electricity

Production of olive oil generates a huge amount of toxic waste, but now there’s a fully functional plant in Spain that eliminates the waste problem.


Carina Lagergren. Photo: Swedish Royal Institute of Technology

It takes about 6 kg olives to produce one liter of olive oil and because Spain is ranked as the world’s largest exporter of olive oil, there are naturally some residual products. The total world production of olive oil is between 2.5 and 3.1 million tons, according to the Agriculture Administration.

Researcher at the Swedish “Kungliga Tekniska högskolan” (Royal Institute of Technology) (KTH), Carina Lagergren, is a senior lecturer at the Institute of Applied Electrochemistry and the person responsible for the research project “Biogas2PEMFC”. The research project is funded by the EU and in addition to KTH also Powercell Sweden AB, Helbio (Greece), Idener, Leitat, Faeca and Ingenostrum (all four from Spain) and Marches Biogas Ltd (UK) and KTH-doctoral student Yasna Acevedo Gomez are involved.

They have now set up a test facility together with San Isidro de Lojas olive oil factory, located in Loja (Granada) located between Malaga and Granada.


From olive oil production. Photo: Swedish Royal Institute of Technology

Today the plant produces around 2 kilowatts of power, but there are plans in the factory to increase the capacity to 200 kilowatts, which would cover half of the olive oil mill consumption. It is possible to have 50% efficiency of the fuel cell, i.e. to convert 50% of the bound energy into electricity, sais Carina Lagergren.

How it works
One starts by putting the waste into a tank, where the waste is decomposed and broken down into biogas, which consists of methane, carbon dioxide and sulfur compounds. In the next step the biogas is converted into hydrogen and carbon dioxide which is then used in a fuel cell. When oxygen is introduced into the fuel cell it reacts with the hydrogen gas which generates both heat and electricity.

The process completely destroys the toxic waste and the residues can safely return to the nature as a fertilizer. Until today the waste has just been stored in large ponds, where the amounts are constantly growing. For this project the most important goal was to find a solution to the waste problem, a way to handle large amounts of residues from olive oil production, says Carina Lagergren. (The waste is also often used as animal food, editors note).

Facts about San Isidro de Lojas
The cooperative was founded in 1958 and currently has over 950 members who together produce over 30 million kg olives. The cooperative olive oil factory produces around 6.5 million liters of olive oil of very high quality. In addition, they produce more than 600,000 kilograms of green asparagus.


Olives ready for harvest. Photo: J.Erixon