Circular Economy and Olive Mill Wastewater Management: From Production to Direct Land Application and Short-Term Effects on Soil Properties

IOSIF KAPELLAKIS^1*Vasileios Tzanakakis²Emmanouil Kabourakis²

• ¹Neapolis University, Paphos, Cyprus
• ²Hellenic Mediterranean University, Crete, Greece

Olive mill wastewater (OMW) is the aqueous and most important by-product generated, mostly from three-phase olive mills (OM), during olive oil extraction from olive fruit. Due to the large quantities produced in short periods of time, OMW high phytotoxicity, and the degree of organic pollution, it creates a serious environmental concern. There are two approaches to effectively manage OMW and its impacts. The first one concerns treatment, consisting of a combination of physical, chemical, and biological processes adopted in a specific and predetermined framework. The second one concerns land treatment and is based completely on natural processes. This refers to high loading rates of pretreated OMW and aims to assess soil treatment potential and address future environmental impacts. However, this approach is not entirely consistent with the principles of circular economy (CE). On the other hand, direct-immediately after production-application of untreated OMW to the orchards that generate it, is considered promising and ensures sustainability and adoption of CE principles through reuse. For this reason, a holistic approach to OMW management was adopted, including all the stages of OMW, from production to application, with the minimum impact. The purpose of this study was to investigate and evaluate current by-product management techniques in the Messara basin, Crete, an area highly affected by increased OMW quantities, and assess short-term effects of OMW land application on soil properties. Analysis of the results indicate that current management practices lack efficiency causing severe environmental impacts, the enforced legal framework concerning land application cannot be fully adopted, while OMW land application onto the olive orchards directly after its production does not cause, as expected considering the literature, any adverse effects on the soil properties instead increases nutrients availability and SOM maintenance was found. The present study provided practical information and guidance regarding OMW application rate and timing to facilitate farmers, policy and decision makers. The findings of the study suggest that direct land application should be considered as an alternative solution to effectively manage the negative impacts of by-products. This is fully consistent with the basic CE principles, climate change adaptation and established sustainable development goals (SDGs).