ABSTRACT
The olive oil production is a key economic sector for the producing countries, mainly in the Mediterranean region. However, the worldwide increasing oil production led to the generation of huge amounts of wastes detrimental for the environment. Therefore, efficient and sustainable management of olive industry wastes has recently acquired significant interest in the scientific research community. In the actual world energy context, various studies dealt with the valorization of the solid/liquid waste streams obtained from the discontinuous/continuous extraction of olive oil for energy purposes. The application of waste-to-energy treatments to these effluents can turn them out into an important energy resource. This review article presents the main used oil extraction techniques and their related research developments. The characterization of the generated wastes and the factors behind their bad environmental impacts are highlighted. Relevant research works related to biochemical and thermochemical conversion of olive mill wastes are extensively reviewed and discussed in terms of product yields and composition. A recent update of the studies addressing olive industry waste applications for energy production is also given. This investigation revealed a lack of studies in relation to the hydrothermal processing of olive mill wastes. Despite their suitability for this process (e.g., high moisture content), few papers have investigated the hydrothermal conversion of these waste streams. This scientific gap opens a very interesting research direction, which has to be further investigated.
Subject(s)
Environment , Olea , Olive Oil , Olea/chemistry , Industrial Waste/analysis , Solid WasteABSTRACT
The agro-industrial activity, which is regarded as a pillar of the North-African economy, is responsible for generating considerable waste quantities. These byproducts can be treated through anaerobic digestion (AD), which offers various financial and ecological benefits over traditional waste disposal methods. However, the transition to this sustainable process is faced with several challenges due to the heterogeneity and seasonality of agro-industrial wastes. In this study, we proposed and evaluated three waste management strategies for treating agro-industrial wastes in large-scale AD plants conceived in specific North-African countries. These strategies involve co-digesting seasonal agro-industrial wastes, i.e., three-phase olive pomace (3POP), grape pomace, and orange peel, with the organic fraction of municipal solid waste (OFMSW) throughout the year (MS1); co-digesting the dominant agro-industrial waste (3POP) with OFMSW during the olive harvest season and mono-digesting OFMSW during the rest of the year (MS2); and co-digesting 3POP and OFMSW year-round by storing 3POP in cold storage facilities (MS3). The techno-economic findings show that the proposed AD plants would be profitable in Morocco and Algeria under both MS1 and MS2, with internal rate of return (IRR) values respectively reaching 10.8% and 18.4% under MS1 and 12.4% and 20.1% under MS2. In contrast, the conceived Tunisian plants would be financially feasible only if MS2 is adopted (IRR of 10.7%). Furthermore, the sensitivity analysis indicates that the economic performance of the proposed plants would mostly be affected by the biomethane selling price and capital cost. Additionally, the carbon footprint analysis suggests that the AD plants could, during their lifetime, reduce the CO2-eq emissions by 411, 208, and 26 Mt (under respectively MS1, MS2, and MS3) compared to the currently used waste disposal practices in the North African region.
ABSTRACT
The energetic performances of seven SOD or RHO-topology ZIFs, with zinc or cobalt metal cation (ZIF-8, ZIF-90, Zn(dcim)2-SALE, ZIF-67, ZIF-7, ZIF-71, ZIF-11) were evaluated using water intrusion-extrusion under high pressure. The relationship between the structural parameters (in particular the pore system SOD or RHO, the type of linker, the metal cation nature) and the intrusion pressure was studied to better understand the mechanism of water intrusion and the energetic behaviour for a given ZIF crystal type. "ZIF-8-water", "ZIF-67-water" and "ZIF-71-water" systems display a shock-absorber behaviour. A very important hysteresis for ZIF-71 and a slight difference between the first intrusion-extrusion cycle and the following ones for ZIF-67 were observed. ZIF-8 (SOD) with zinc cation and ZIF-67 (SOD) with cobalt cation display similar intrusion pressures. For ZIF-71 (RHO) material, the stored energy is more than doubled compared to ZIF-8 and ZIF-67 (SOD). This might be related to the topology. No water intrusion was observed after three water intrusion-extrusion cycles, for the ZIF-90 (SOD), Zn(dcim)2-SALE (SOD), ZIF-7 (SOD) and ZIF-11 (RHO) materials. This is explained in term of hydrophilic feature as well as topology and linker effects.
ABSTRACT
Experimental water intrusion-extrusion isotherms were obtained at room temperature on pure silica ITW-type zeolites (ITQ-12 zeosil). The water intrusion is obtained by applying a high hydraulic pressure corresponding to the intrusion step. When the pressure is released, the water extrusion occurs at a similar pressure to that of the intrusion one. Therefore, the "ITW zeosil-water" system behaves like a spring and the phenomenon is reproducible over several cycles. Several characterization techniques have been performed before and after water intrusion-extrusion experiments in order to reveal the presence or the lack of defects after such experiments. Structural modifications at the long range order cannot be observed by XRD analysis after three water intrusion-extrusion cycles. However, solid state NMR spectroscopy provides evidence of the presence of Q3 groups revealing the breaking of some siloxane bridges after the intrusion step. The "ITW zeosil-water" system can restore 100% of the stored energy corresponding to about 8 J g(-1).
