UNIVERSITÉ PAUL CÉZANNE, AIX MARSEILLE III - IMEP

Résultats et discussion. Chapitre 5: Disponibilité des substrats oléicoles
Nowadays, in most countries which still use the three phase extraction technology, the
current practice to deal with OMW consists either to use it as amendment in olive fields or to
store it in evaporation ponds in order to reduce the volume to dispose off. Field amendment
which has the advantage to return to the soil part of the nutrients (N, P, minerals) exported
with OMW is a highly controversial practice in the scientific community (Mekki et al., 2007),
while the efficiency of the evaporation ponds is often very poor despite their high
construction costs to avoid OMW infiltration into the ground water.
OMW drying is actually a slow process since the olive oil and some mucilage cover
the surface and make it impermeable to water (Jimenez and Lao, 2004). As so, OMW drying
could be improved by increasing the surface of exchange with the atmosphere through the
addition of a high surface absorbing solid matrix. The OC readily available from the same
olive mill could be a good candidate for that. Thus, the amount of wastes, generated by olive
mill, could be controlled, based on the assumption that the resulting product could be
valorised in the same way as crude OC.
Open sun drying is the common drying method of agricultural materials used in
Morocco. However, this method results in long drying times and quality loses since the drying
materials are directly exposed to environmental conditions (Erbay and Icier, 2009). On the
other hand, artificial hot air dryers have high investment cost and high energy expenses
(Colak and Hepbasli, 2007). However, solar drying in greenhouse can be considered as an
advancement of natural sun drying and it is a more efficient technique of utilizing the
potential solar energy (Müller et al., 1989; Jain and Tiwari, 2004; Kooli et al., 2007; Janjai et
al., 2009). Many research and performance studies have been reported on solar drying in
greenhouse (Kooli et al., 2007; Janjai et al., 2009). Therewith, certain studies were focused on
OC drying for soap making, animal feed or fertilizer (Haddadin et al., 2002; Akgun and
Doymaz, 2005). Nevertheless, there have been no reports on the drying of the mixture of olive
cake with OMW in the literature.
The objectives of the present study were to determine under which conditions all the
OMW generated by a mill could be absorbed by the OC produced by the same mill and if the
resulting OC-OMW mixture could be dried to 10% (w/w) humidity in order to obtain a solid
matrix which could be valorized in the same way as crude OC. To achieve these objectives
we (1) performed a mass balance of the different products generated by a traditional maasra
mill (2) determined the OMW retention capacity by the mill OC, (3) performed several drying
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