Olive oil by-products: From harmful waste to interesting carbonaceous materials : Hydrothermal conversion of olive oil by-products into carbon rich chars

In this paper, four (04) olive oil by-products were used as potential feedstocks for the production of carbon rich materials via hydrothermal carbonization (HTC) process. The raw olive pomace (ROP), Olive mill waste (OMW), Impregnated ROP (IROP) were introduced into a hydrothermal calorific bomb at different experimental conditions. The effect of carbonization temperature was followed for three different isotherm peaks. Results showed that mass yield decreases with increasing heating temperature. The IROP presented the highest yield of 65% at a carbonization temperature of 180°C. Thermogravimetric analysis on the produced hydrochars depicted a high amount of volatile matter content reaching 85% for OMW carbonization at 220°C. SEM imaging showed a similar pattern for the different hydrochars characterized with the appearance of a spherical-like morphology. FTIR specters emphasized on the amorphous aspect of the produced hydrochars with a significant concentration of acidic and basic surface functional groups.