Is Olive Oil Sustainable?
Is Olive Oil Sustainable? A Study of Olives, Carbon and Climate Change
We are often asked whether the cultivation and harvesting of olives is sustainable. It is a very good question – and one that deserves a little examination.
First, though, what do we actually mean by sustainable?
The most often quoted definition comes from the UN World Commission on Environment and Development:
“Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.”
With that definition in mind, let's look at the olive tree.
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Olive Trees and Carbon Capture
Across the globe there are some 11 million hectares of olive trees, forming what has been described as the world's largest man-made forest.
Those olive groves are estimated to remove around 4.5 tonnes of carbon dioxide per hectare from the atmosphere each year – equivalent to approximately 49.5 million tonnes of CO₂ annually.
But there is a human story here too.
These are not simply trees growing in isolation. They are trees planted, cultivated, harvested and tended by people who depend upon them for their livelihoods, often continuing agricultural traditions that stretch back through generations.
That combination of environmental and human value is an important part of the sustainability story.
The Importance of Olives to the European Economy
The environmental and financial significance of the olive harvest to Europe is difficult to overstate.
Of the EU's approximately five million hectares of olive groves, more than half are in Spain. Around 35% of Spain's farm workers work with olives, while almost 74% of the EU's olive oil is produced in Spain, with a further 22% divided approximately equally between Greece and Italy.
The European Union is the world's largest olive oil producer, with the majority of its olive oil coming from nine countries: Spain, Italy, Greece, Portugal, France, Croatia, Slovenia, Cyprus and Malta.
Olives, then, are much more than a food crop. They support rural communities, employment and economies across large areas of the Mediterranean.
Is Olive Oil Carbon Positive?
The environmental story becomes even more interesting when we look at the carbon balance of olive oil itself.
The International Olive Council has estimated that the production of one litre of olive oil has a positive carbon balance, reducing more than 10 kilograms of carbon dioxide from the atmosphere.
That is a remarkable claim and helps illustrate why the olive tree has become an interesting part of the wider discussion around agriculture and climate change.
There is, however, another side to the story.
Climate Change and Mediterranean Soils
As climate change takes effect and temperatures rise, the ability of soils to absorb carbon and retain phosphorus can decline dramatically.
For olive growers – and Mediterranean agriculture more generally – that presents an obvious challenge.
An innovative study led by the University of Córdoba (UCO), in collaboration with the School of Environmental and Natural Sciences at Bangor University in the UK, examined how different Mediterranean soils respond to heat stress.
The research identified a clear threshold at which soil function begins to decline.
At around 40°C, microorganisms become less able to capture carbon. By 50°C, that function is almost entirely lost.
Phosphorus reserves also fall sharply as temperatures rise, with availability becoming very limited above 40°C.
But the researchers also investigated something rather interesting: whether a by-product of olive oil production could help.
What Is Alperujo?
One of the principal by-products of olive oil production is alperujo.
It is a nutrient-rich, wet, semi-solid mixture of olive pulp, skin, stone and vegetation water left behind during the olive oil production process.
Traditionally, alperujo can be environmentally challenging if left untreated because it is highly acidic.
In other words, it might easily be regarded simply as waste.
But the researchers discovered that it could potentially become something rather more useful.
Turning an Olive Oil By-Product Back Into Healthy Soil
The University of Córdoba team tested two Mediterranean soils: a chalk-rich soil from Córdoba and a more acidic soil from Badajoz.
Both were exposed to temperatures ranging from 20°C to 50°C.
The researchers then tested whether adding organic materials to the soils could help them withstand increasing temperatures.
After two weeks, the organic amendments had significantly improved soil resistance and phosphorus availability.
And of the materials tested, alperujo was the most effective, strengthening soil resistance at temperatures of up to 50°C.
There is something rather pleasing about this.
A material produced as a by-product of making olive oil – and which can itself present an environmental problem if not properly managed – may be capable of helping the very soils upon which future olive cultivation depends.
It also demonstrates how almost every element of the olive can potentially be put to good use for the benefit of the land.
A More Circular Olive Industry
This is an important part of the sustainability story.
The olive tree produces the fruit. The fruit produces the oil. And material left behind after producing that oil can potentially be returned to the soil to help make it more resilient.
Those healthier, more resilient soils can then support the olive trees that continue to remove carbon dioxide from the atmosphere.
It is a good example of how traditional agriculture and modern scientific research can work together to find new uses for something previously regarded as waste.
And, as temperatures across the Mediterranean continue to rise, innovations such as these could become increasingly important.
Putting 49.5 Million Tonnes of CO₂ Into Perspective
It is difficult to visualise what 49.5 million tonnes of carbon dioxide actually means.
So here's one way of looking at it.
A one-way flight from London to New York generates an average of about 400kg of CO₂ per passenger.
On that basis, the estimated 49.5 million tonnes of CO₂ absorbed annually by the world's olive trees is equivalent to the emissions generated by almost 124 million passengers flying one way from London to New York.
Based on the comparison in our original study, that would be enough to offset the total number of passengers flying that route for more than 30 years.
It puts the scale of those millions of olive trees quietly doing their work into rather better perspective.
So, Is Olive Oil Sustainable?
Which brings us back to where we started.
“Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.”
No agricultural system is without environmental impact, and there are clearly many different aspects of olive oil production to consider – from cultivation and irrigation to harvesting, milling, packaging and transportation.
But on the evidence examined here, the olive tree has quite a story to tell.
It provides livelihoods for millions of people, supports rural economies and communities, captures substantial amounts of carbon dioxide and produces a crop from which even a potentially troublesome by-product may be capable of being returned to the land to help protect future soils.
So, is the olive tree sustainable?
It would certainly appear to be – at least on one level.
Giles Henschel
Founder, Olives Et Al
