This study evaluates and demonstrates the potential use of the solid fraction from the digestate of thermophilic (55˚C) anaerobic digestion of olive mills’ wastewater (OMW) after sun drying and screening for too large clumps of sludge, collected several times through the thermophilic digestion, as an alternative cultivation medium for the horticulture industry. Integrating this fraction within plants’ cultivation medium demonstrates a circular-economy approach, transforming an environmental pollutant, OMW, into a valuable input for horticulture. Replacing peat with OMW-derived digestate fraction is particularly important given the severe environmental impacts associated with peat excavation. It aims to show horticulturists that adoption of its use offers direct economic benefits, avoiding peat costs while simultaneously reducing environmental burdens and GHG emissions. The findings are based on successful experiments where OMW-digestate solid fraction was tested as a peat substitute in the cultivation mediums of plants. The positive results demonstrate the potential benefits of its use as a peat substitute for horticulture. The use of digestate from the anaerobic process as a peat substitute for horticulture allows full utilization of all the products of oil mill wastewater treatment: biogas for energy and digestate as cultivation media for horticulture. The result of this study also indicates that the possible use of OMW-digestate as a peat substitute in horticulture can reduce peat extraction, thereby helping to conserve a natural resource while contributing to the economic development of both the horticulture and olive oil production sectors.
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