Olive Mill by-Products Thermochemical Conversion via Hydrothermal Carbonization and Slow Pyrolysis: Detailed Comparison between the Generated Hydrochars and Biochars Characteristics

Ahmed Amine Azzaz,Mejdi Jeguirim,Camélia Matei Ghimbeu,Salah Jellai,Leila El-Bassi

doi:10.3390/pr10020231

Abstract

In this research work, an ecofriendly approach was adopted for the treatment of two abundant liquid and solid agricultural wastes generated by olive mill industry: olive mill wastewater (OMWW) and raw olive pomace (ROP). It consists, firstly of the impregnation of ROP by OMWW and the conversion of the resulting impregnated sample (IROP) into hydrochars and biochars through hydrothermal carbonization (HTC) and slow pyrolysis methods, respectively. The impact of the treatment temperature on the physico-chemical properties of the derived chars was assessed by various analytical techniques. The hydrochars production yields were found to be higher than the biochars ones and associated to the lower temperature used. However, the generated biochars possess higher carbon percentage and lower volatile matter contents. In addition, the increase of the hydrothermal and pyrolysis carbonization temperatures shows an increase of macro-elements contents and a significant decrease of the O/C ratios which led to an enhancement of the high heating value for both hydrochars and biochars. The FTIR and Boehm titration analysis highlighted a significant alteration of the biochars surface chemistry compared to hydrochars evidenced by the lower amount of functional groups. The collected data emphasize on the efficient potential application of hydrochars and biochars for agricultural and environmental applications, respectively. Furthermore, it was noted that both chars have high energetic potentials and could be used for co-firing with coal in industrial boilers.

Highlights

For temperatures between 180 ◦ C and 220 ◦ C, respectively (Figure 1). These yields are in agreement with the values reported in previous papers investigating the hydrothermal carbonization of biomasses [34,35]
Hydrochars and biochars from raw olive pomace impregnated with olive mill wastewaters were synthesized under different experimental conditions and characterized in depth
Results showed that the final products presented significantly different physico-chemical properties that are intimately related to the used treatment process

Summary

Introduction

The agri-food industry played a very important role in the development of agriculture related sectors [1]. The processing industry for extensively consumed agricultural products such as cereals, vegetables, fruits, animal-source products, and oils occupies an important place in worldwide economies and especially in developing countries [2]. The majority of these industries generate various wastes that have to be seriously taken into consideration in order to avoid any negative effects on the environment and human health [3]. The sustainable management of agri-food industry wastes presents very interesting valorization potentials in agricultural, environmental and energetic sectors [4,5]

Objectives

Methods

Results

Conclusion