The olive industry is quite large in South Africa, particularly in the Western Cape where the fruits are grown in similar climates to grapes. Olives are mainly pickled, packaged and sold for consumption, or are crushed and pressed to make olive oil.
The process of making silky smooth olive oil begins with the fruit being crushed and mixed with water in mills. Natural oils inside the olives are released and float on the surface of the water, where it is collected and refined. Usually, the solid waste and murky water left behind are then discarded – and therein lies the problem.
Usually, this olive wastewater is simply pumped into waterways. The wastewater has detrimental effects on the water system as it pollutes the clean water and can actually affect the pH balance of farm soils when pumped back onto crops. This alters the chemical balance of the soil which can reduce crop yields and have long-term effects on the future fertility of the soil.
Alternative methods of disposing olive oil waste
Throwing away this olive mulch is a wasteful and unsustainable practice, but new methods of repurposing this byproduct are being experimented with. The olive mill wastewater can actually be used as fertiliser, converted into biofuel or treated to create clean water once again.
A team of scientists in France have experimented with some alternative means of using this olive wastewater. They mixed it with sawdust (another waste product in the timber industry) and dried it out. They collected the clean water as it evaporated, which is suitable for crop irrigation.
The dried mixture was then subjected to pyrolysis (exposing it to high temperatures in the absence of oxygen) to create charcoal pellets and a combustible gas. The gas was collected and condensed into biofuel and the nutrient-rich charcoal was used as a crop fertilizer.
The scientists concluded that the charcoal pellets significantly improved plant growth. This entire process needs further refinement but similar facilities to process the wastewater in South Africa can be constructed.
This will make the entire industry more sustainable as the byproducts of producing olive oil can now be used in the process of growing the plants. The biofuel can be used to power the pyrolysis process, the charcoal pellets can be an alternative source of fertiliser for the crops, and the clean water collected from the evaporation process can be used to irrigate the plantations.
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