Chapter 2 Olive mill waste: recent advances for the sustainable development of olive oil industry

Abstract Olive oil industry grows constantly in specific parts of the world. About 750 million olive trees are cultivated and approximately 2.95 million tons of olive oil are produced annually. Most olive oil (98%) is produced in the Mediterranean region, mainly between October and February. Olive oil production results in an annual generation of more than 30 million m3 of olive mills wastes (OMW). Although several techniques have been developed and patented for OMW management, detoxification and valorization, their application is often too expensive for most olive-oil mills, in which the Mediterranean region are usually small family businesses. The uncontrolled disposal of OMW on soil may cause strong phytotoxic and antimicrobial effects, may increase soil hydrophobicity, decrease water retention and infiltration rate, may also affect acidity, salinity, N immobilization, microbial activity, nutrient leaching, lipids concentration, organic acids, and naturally occurred phenols. In surface waters it may decrease the dissolved oxygen content, increase the organic matter and K, Fe, Zn, and Mn contents. On the other hand, the remaining sludge, after evaporation of the liquid fraction of the wastes, contains almost 94% organic matter and although it could be highly beneficial to agricultural soil, it has been shown that it also contains toxic compounds and oil that may increase soil hydrophobicity and decrease water retention and infiltration rate if applied to soil. This chapter introduces the current advisable practices for the sustainable development of olive oil industry as well as two soil remediation methods, applied in the framework of the LIFE project PROSODOL (LIFE07 ENV/GR/280), at a pilot OMW disposal area in Greece, that is, bioremediation and zeolite incorporation in soil. In the framework of PROSODOL project specific actions, measures, and means suitable for Mediterranean countries were proposed to the European Commission and are presented in this chapter