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Extracting pomace olive oil has been identified as the most sustainable alternative for valorising the by-products of the olive oil industry, according to a methodology developed by the University of Cordoba that takes economic, environmental and social indicators into account. The olive oil industry offers a good example of how sustainability challenges can be tackled in the agri-food sector. Every olive harvest generates tonnes of alperujo, the main by-product of olive oil extraction, a residue that requires careful management. For decades, mills have followed a circular-economy path, developing various ways to make use of olive pomace that go well beyond simply avoiding pollution.
The three main alternatives currently used by mills to add value to this by-product on an industrial scale are: extraction of pomace olive oil, which is used for cooking, mainly in the hospitality sector, and which in turn generates a further by-product, dried pomace or orujillo, used for energy generation; composting, which produces organic fertiliser; and gasification, a technology that enables the production of renewable energy and biochar, a material useful for improving soil quality and retaining carbon.
Which of the three options is the most sustainable? That is the question researchers David Bolonio, Rubén Granado, José A. Gómez Limón and Anastasio J. Villanueva, members of the University of Cordoba's WEARE research group, have set out to answer. The study was published in the journal Business Strategy and the Environment.
The analysis does not focus solely on the environmental dimension. One of the study's main contributions is a methodology that jointly assesses the environmental, economic and social impacts of each alternative. As Gómez Limón explains: "In doing so, we answer the sector's question about which technology is the most sustainable one that a mill could choose to implement."
David Bolonio explained: "The methodology we developed includes a life-cycle analysis to assess the environmental dimension; economic indicators relating to the investment required, economic risk and the profitability of each alternative; and indicators showing the social significance of each option, linked to job creation, job quality and seasonality."
Anastasio Villanueva pointed out the importance of "introducing a factor of uncertainty: through statistical techniques, we factor in the probability of changes in the electricity market, for example, which affects the profitability of one option or another depending on the season."
Applying this three-pronged methodology produces a composite overall sustainability index. Using this approach, the most sustainable option at present is pomace olive oil extraction, which is also the most widely applied option in the sector. For mills, this alternative is the most attractive from an economic standpoint, as it requires no investment and carries lower risk.
However, when other factors of environmental and social importance are taken into account, such as reducing emissions or creating higher-quality jobs, alternatives such as gasification offer clear advantages, ranking immediately after extraction in the overall calculation. Composting comes third in this ranking, notable for its contribution to rural employment and its benefits for agricultural soils, even though its economic profitability is currently more limited.
According to Gómez Limón, one conclusion is "that the sector has long been heading in the right direction, since the most sustainable method is the one most widely applied today."
Not a clear-cut choice
Another conclusion is that the overall differences between the alternatives are not very large. This means that small changes, in energy prices, demand for organic fertilisers, or public policy for example, could tip the balance towards options that are more beneficial to society as a whole. The specific circumstances of each mill must also be considered: mills located far from pomace extraction plants face significant transport costs, making gasification a more profitable option for them.
As the study shows, the alternatives with the greatest environmental and social benefits are not always the most profitable for private companies. The authors therefore highlight the importance of designing public policies that incentivise the options that are most environmentally friendly and employment-generating, whether through investment aid, financial instruments, or mechanisms that recognise the social and environmental value created.