Hazards of Olive Oil Wastes

The olive oil industry offers valuable opportunities to farmers in terms of seasonal employment as well as significant employment to the off-farm milling and processing industry.  While this industry has significant economic benefits in regards to profit and jobs; the downside is it leads to severe environmental harm and degradation.

Sources of Wastes

Currently, there are two processes that are used for the extraction of olive oil, the three-phase and the two-phase. Both systems generate large amounts of byproducts.  The two byproducts  produced by the three-phase system are a solid residue known as olive press cake (OPC) and large amounts of aqueous liquid known as olive-mill wastewater (OMW).  The three-phase process usually yields 20% olive oil, 30% OPC waste, and 50% OMW.  This equates to 80% more waste being produced than actual product.

More contemporary is the two-phase system, in this system “the volume of OMW produced is reduced because less water is used and much of that water and toxic substances are held within the solid olive cake, thus producing a semi-solid residue (SOR).” While the two-phase system produces less OMW, the SOR it produces has a “high organic matter concentration giving an elevated polluting load and it cannot be easily handled by traditional technology which deals with the conventional three-phase olive cake.”

Unhealthy Effects of ‘Healthy Oil’

Regardless of system used, the effluents produced from olive oil production exhibit highly phytotoxic and antimicrobial properties, mainly due to phenols.  Phenols are a poisonous caustic crystalline compound.  These effluents unless disposed of properly can result in serious environmental damage.  Troublingly, there is no general policy for disposal of this waste in the olive oil producing nations around the world.  This results in inconsistent monitoring and non-uniform application of guidelines across these regions.

Olive mill wastewater cannot be sent to ordinary wastewater treatment systems, thus, safe disposal of this waste is of serious environmental concern.  Moreover, due to its complex compounds, olive processing waste (OPW) is not easily biodegradable and needs to be detoxified before it can properly be used in agricultural and other industrial processes.

This poses a serious problem when the sophisticated treatment and detoxification solutions needed are too expensive for developing countries such as Morocco, Algeria and Tunisia where it is common for OMW to be dumped into rivers and lakes or used for farming irrigation.  This results in the contamination of ground water and eutrophication of lakes, rivers and canals.

Eutrophication results in reductions in aquatic plants, fish and other animal populations as it promotes excessive growth of algae. As the algae die and decompose, high levels of organic matter and the decomposing organisms deplete the water of oxygen, causing aquatic populations to plummet.

Another common tactic for disposal of olive mill wastewater is to collect and retain it in large evaporation basins or ponds.  It is then dried to a semi-solid fraction. In less developed countries where olive processing wastes is disposed of, this waste, as well as olive processing cake and SOR waste is commonly unloaded and spread across the surrounding lands where it sits building up throughout the olive oil production season.

Over time these toxic compounds accumulate in the soil, saturating it, and are often transported by rain water to other nearby areas, causing serious hazardous runoff. Because these effluents are generally untreated it leads to land degradation, soil contamination as well as contamination of groundwater and of the water table itself.

Even a small quantity of olive wastewater in contact with groundwater has the potential to cause significant pollution to drinking water sources. The problem is more serious where chlorine is used to disinfect drinking water. Chlorine in contact with phenol reacts to form chlorophenol which is even more dangerous to human health than phenol alone.

Catherine Hansen

Catherine Hansen is a returned Peace Corps volunteer and graduate from West Virginia University, where she studied for her Masters in Sustainable Development. She recently returned from a 27-month service in Morocco where she was serving as a Youth Development volunteer designing literacy, health, and environmental programming for youth in collaboration with local associations and volunteers. One of her main life goals is to share her passion for protecting the environment from human harm by bringing awareness to environmental issues that are often times over looked.Through outreach and education, Catherine hopes to inspire a refreshed appreciation for our natural world. She aims to begin her career in environmental services within the year.

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