COMPOST PREPARED WITH TWO PHASE OLIVE MILL WASTE "ALPERUJO" AS GROWING MEDIA

The olive oil industry is very important in Mediterranean countries, and especially in Spain which is the main world producer. In Spain, two-phase olive mill waste (TPOMW), “alperujo” is the main by-product generated during olive oil extrac¬tion. Composting as a method for preparing organic fertilizers and amendments is economically and ecologically sound and may well represent an acceptable solution for disposing of TPOMW. The objective of this work was to prepare a TPOMW compost from the most common wastes produced in a typical olive mill (TPOMW and olive tree leaves) and to characterize its main physical and chemical properties to evaluate its potential as growing media. The compost was prepared in a pilot-plant using the turning-pile system using a mixture of TPOMW, olive leaf as bulking agents and urea as nitrogen source. The quality of the mature compost was assessed by the following parameters: moisture, bulk density, water-holding capacity, pH, electrical conductivity (EC), cation exchange capacity (CEC), organic matter (OM), N, P, K, C/N ratio, germination index (GI). Different growing media were prepared by mixing TPOMW compost and peat in different proportion (0, 25, 50, and 75%) and they were evaluated for the germination of tomato and watermelon seeds. TPOMW compost showed favorable physicochemical properties which may be valuable if used as growing media. Another important advantage of this compost is the organic matter concentration and that it is free of heavy metals and other potential pollutants.