The olive tree and olive oil industry is one of the main economic drivers in Andalusia (Spain). It provides work to close to 250,000 people and accounts for 40% of agricultural jobs.
The production of olive oil is a source of wealth for hundreds of municipalities in the Autonomous Community but, as with any other industry, there are some environmental challenges associated with it. Extracting the oil mechanically in the mills produces, in addition to the precious liquid, another product known as pomace or olive pulp (alperujo), which must be treated to prevent it becoming a source of pollution.
Located in an area renowned for its olive production, the two industrial complexes of Sacyr Industrial in Andalusia have the purpose of maximising the recovery of energy of the biomass from the olive groves. In addition to these complexes, Sacyr Industrial has three more cogeneration plants, associated with similar facilities. These plants generate over 920 GWh a year, equivalent to the consumption of close to 270,000 households. And, thanks to them, each year this prevents the emission of nearly 170,000 tonnes of CO2.
Exploiting olive pulp waste
The facilities at Sacyr Industrial are designed to transform the olive pulp generated in the plants' influence zones into energy. The pulp is put through drying and extraction treatments so it can serve as biomass to generate electrical energy sustainably.
The complexes boast three facilities with differentiated activities: a cogeneration plant to dry the pulp, an oil extraction facility and a biomass electrical energy generation plant.
The first of these facilities, the cogeneration plant, has natural gas engines or gas and steam turbines used in a combined cycle system, whose exhaust gases are used to dry the pulp. At the same time, these engines and turbines generate electrical power, which is fed into the grid.
In the drier, the pulp's humidity level is reduced, which makes it possible to extract the oil it contains. Once the oil has been extracted, what is left is known as pomace, which is the end energy product of the process that began in the mill.
Biomass from the olive groves themselves
The biomass plant produces electrical power which is fed into the grid, using the pomace generated and other biomass collected in the area (mainly cuttings from pruning the olive groves themselves) as fuel.
After harvesting the olives, the olive trees have to be cleaned up and made ready for a new season; this generates large amounts of leaves and cuttings. Historically, this biomass was burnt in the olive groves but, in the plants' influence zones, farmers are preferring to monetise it, by selling it to the biomass plant as fuel. In fact, 43% of the biomass consumption at the Sacyr Industrial plants, nearly 80,000 tonnes, comes from leaves and cuttings.
The burning of this biomass in the plant's furnace represents a great environmental improvement, as in this way controls are greater and it is subject to strict emissions regulations.