Olive Mill Waste Research Articles

Upcycling olive pomace into pectic elicitors for plant immunity and disease protection

Olive oil production generates substantial quantities of pomace, which are often disposed of in soil, leading to adverse effects on agriculture and the environment. Furthermore, climate change exacerbates plant diseases and promotes the use of toxic phytochemicals in agriculture. However, olive mill wastes can have high potential as reusable and valuable bioresources. Using diluted ethanol, an environmentally friendly solvent, we extracted a fraction containing short and long oligogalacturonides, short arabino-oligosaccharides and polysaccharides. The obtained extract elicited key features of plant innate immunity in Arabidopsis seedlings, including the phosphorylation of mitogen-activated protein kinases MPK3 and MPK6 and the upregulation of defence genes such as CYP81F2, WRKY33, WRKY53, and FRK1. Notably, pretreatment of adult Arabidopsis and tomato plants with the olive pomace extract primed defence responses and enhanced their resistance to the phytopathogens Botrytis cinerea and Pseudomonas syringae. Our results highlight the opportunity to upcycle the two-phase olive pomace collected at the late stage of olive oil campaign, in low-cost and sustainable glycan elicitors, contributing to reducing the use of chemically synthesized pesticides.

Eco-friendly remedies for soil contamination: manufacturing and analysis of nanobiochar using sugarcane bagasse and olive mill waste.

Soil degradation poses a significant challenge to Egypt's agriculture, making resource optimization essential. Nanobiochar presents a promising solution for pollutant removal; however, its low yields may hinder commercialization. This study investigates the production of biochar from sugarcane bagasse and olive mill waste, focusing on its composition, morphology, and effectiveness in soil immobilization. Advanced techniques like SEM, TEM, and FTIR were used to characterize the nanobiochar, highlighting its potential as a sustainable solution to soil contamination. The study revealed that ZnCl2 treatment significantly lowers pH, while KOH modification raises it. Surface morphology analysis showed that SCB biochar exhibited a highly porous structure, while OMW biochar had less porous edges and irregular oval-shaped pores. The effects of biochar activation on the availability of heavy metals like Ni, Pb, and Mo (in mg.Kg-1) were also examined. Ni concentrations decreased from 1.27mg.Kg-1 in untreated biochar (NA) to 0.78mg.Kg-1 in KOH-treated biochar (KA) and 0.67mg.Kg-1 in ZnCl2-treated biochar (ZnA). Pb levels dropped from 7.7mg.Kg-1 in NA to 5.2mg.Kg-1 in KA and slightly to 4.74mg.Kg-1 in ZnA. Mo showed a similar trend, with the highest concentration in NA at 1.21mg.Kg-1, followed by 0.88mg.Kg-1 in KA and 0.75mg.Kg-1 in ZnA. Overall, OMW nanobiochar demonstrated a greener, more sustainable solution to soil contamination compared to SCB nanobiochar.

Microalgal Phenolics: Systematic Review with a Focus on Methodological Assessment and Meta-Analysis.

A critical review and analysis of the literature relevant to the phenolic content of eucaryotic microalgae was performed. Several issues were identified and discussed. In summary, the main problems with the reporting on the phenolic content of microalgae are the following: (1) despite its usefulness in the determination of phenolic content in plant samples, the Folin-Ciocalteu assay is non-suitable for microalgal research due to the high presence of interfering compounds in microalgal extracts such as chlorophyll and its derivatives in organic extracts and free aromatic amino acids or nucleotides in aqueous extracts; (2) while there is chromatographic evidence for the presence of simple phenolic acids in most microalgal clades, the lack of critical enzymes of phenolic biosynthesis in most microalgae, as well as the high variability of phenolic profiles even in the same genus, require more extensive research before conclusions are drawn; (3) the accumulation and metabolism of external phenolics by microalgae has been almost universally neglected in studies focusing on the phenolic content of microalgae, even when natural seawater or complex organic media are used in the cultivation process. Despite these issues, the literature focusing on the bioremediation of waste streams rich in phenolics through microalgae demonstrates the ability of those organisms to adsorb, internalize, and in many cases oxidize or transform a wide range of phenolic compounds, even at very high concentrations. Simple phenolics found in waste streams, such as olive mill waste, have been shown to enhance the antioxidant activity and various bioactivities of microalgal extracts, while complex biotransformation products of phenolics have also been characterized. In conclusion, the de novo biosynthesis of phenolic compounds via eucaryotic microalgae requires further investigation with better designed experiments and suitable analytical methods, while the response of microalgae to phenolic compounds in their growth medium is of great practical interest, both in terms of waste treatment and for the production of functional foods, cosmetics, and pharmaceuticals.

Design of New Partially Bio-Based Polyguanamines for the Reversible Adsorption of Phenolic Molecules from Olive Mill Wastes

Design of New Partially Bio-Based Polyguanamines for the Reversible Adsorption of Phenolic Molecules from Olive Mill Wastes

Comparing how compost and manure affect soil organic matter using a complete factorial design

BackgroundThe aim of this study was to determine the influence of physico-chemical factors on soil organic matter by comparing two types of soil improver: one produced from olive mill waste cake residues (CRPM) and the other from manure (CF). This was achieved using Full Factorial Design, the main objective of which is to measure precisely the impact of each factor on a given response, to analyze the interactions between the various factors and to identify the optimum conditions for achieving a specific objective or improving the performance of a process. MethodsFour independent factors were studied: pH, electrical conductivity, humidity and carbon/nitrogen (C/N) ratio. Using design, based on their significance, coefficient of determination, analysis of variance and Pareto charts, the interactions between these variables were assessed to identify those with the most positive impact on soil fertility. ResultsThe results show that, for CRPM compost, the most positive interaction is between pH and ratio C/N. For manure, the interaction between pH and moisture has the greatest beneficial effect. These findings underline the importance of controlling all three factors − pH, moisture and ratio C/N to optimize soil fertility. ConclusionsThe analysis confirmed the reliability of the models used, with p-values below 0.05 and coefficients of determination (R2 and adjusted R2) close to 1, indicating the robustness of the models. Pareto diagrams were used to precisely identify the most relevant interactions for improving soil amendment management.

Use of carbon-encapsulated zero-valent iron nanoparticles from waste biomass to hydrogen sulphide wet removal.

This study evaluates the use of carbon-encapsulated zero-valent iron nanoparticles for biogas upgrading in wet systems. The nanoparticles were produced by hydrothermal carbonization, using olive mill waste (OMW) or microalgae as carbon sources. The solids were characterized to investigate the specific surface area, total and zero-valent iron content, pHPZC and chemical and crystalline composition. Their adsorption performance towards hydrogen sulphide (H2S) was tested by treating two types of synthetic biogas with and without CO2. In both cases, the starting H2S concentration was approximately 60 ppm and the experiments lasted until the complete saturation of the nanoparticles. Optimal Fe/C ratios of 0.05 for OMW nanoparticles and 0.2 for microalgae nanoparticles demonstrated H2S-specific adsorption capacities of 9.66 and 9.55 , respectively, in a synthetic biogas without CO2. The addition of CO2 in biogas reduced adsorption, possibly due to system acidification. X-ray photoelectron spectroscopy analysis revealed surface compounds on the surface of the spent nanoparticles, including disulphides, polysulphides and sulphate. The saturated adsorbents were effectively regenerated with air, leading to the oxidation of sulphur species and desorption. The regeneration allowed a total adsorption capacity of 53.25 and 34.14 , after 10 consecutive cycles of adsorption/regeneration with a single batch of olive mill and microalgae nanoparticles, respectively.

Integrated Impact of Olive Mill Wastes and Semi-Circular Bunds on Soil Properties and Rainwater Harvesting Efficiency in Egypt’s Northwestern Coastal Zone

ABSTRACT The productivity of olive in the northwestern coastal zone of Egypt is significantly constrained by drought and low organic matter in the soil. This study addresses these challenges by exploring the synergistic effects of olive mill wastes (OMW) application and micro-catchment water harvesting techniques on soil properties, runoff, moisture storage, and rainwater harvesting efficiency. Field experiments were conducted over two winter seasons, employing different micro-catchment structures (semi-circular and triangular bunds) and OMW applications. The results revealed that the integration of semi-circular bunds with OMW application (T4) substantially increased rainwater harvesting efficiency by 67.7% and 46.4% in the first and second seasons, respectively. Additionally, T4 and T5 exhibited reduced runoff by 47.8% and 41.3% in the first season and 49.4% and 38.9% in the second season, respectively. T4 significantly enhanced soil organic matter, soil macronutrients (N, P, and K), and micronutrients (Fe, Mn, Zn, and Cu) compared to the control (T1). The study highlights the effectiveness of T4 in improving soil moisture, reducing soil erosion, and enhancing soil fertility. This integrated approach involving OMW application within a semi-circular bund as a water harvesting system proves to be a promising strategy for sustainable olive cultivation in arid conditions.

Adsorbents Produced from Olive Mill Waste and Modified to Perform Phenolic Compound Removal

Olive mill waste (olive pomace, OP, and olive stone, OS) was used in this work to produce adsorbents for the removal of five phenolic acids typically found in olive mill wastewater. OP and OS were subjected to different treatments (combined or not) that were chemically modified (NaOH) or physically modified by two different methods, incipient wetness impregnation (IWI) and hydrothermal deposition (HD), and even biochar production obtaining a total of 16 materials. The materials were characterized by different analytical techniques such as N2 absorption, scanning electron microscopy, infrared spectroscopy, and pH zero-potential charge. The mixture of five phenolic acids was used to evaluate in batch conditions the adsorption capacity of the prepared materials. OS chemically modified with IWI (OSM-IWI) and OS biochar with HD (BOS-HD) presented better adsorption capacity at 157.1 and 163.6 mg/g of phenolic acids, respectively, from a total of 200 mg/g. For some materials, the surface area cannot be correlated with adsorption capacity, unlike pHzpc, where high values fit better adsorption rates. The infrared spectroscopy profile indicates the presence of O-H and N-H functional groups and, the last one, red-shifted in the IWI preparation compared to the HD one. In addition to this, the prepared material from olive mill waste can be suitably used for the mixture of phenolic compounds.

Optimization of industrial-scale composting of dewatered pig slurry and olive mill waste using discarded tennis balls as an inert bulking agent

Material shortages in composting may pose limits or logistical problems in certain regions, which can be addressed with inert and reusable wastes. Very little research has been conducted on the subject of using alternative synthetic wastes as structuring agents to improve composting process parameters. The present work aimed to evaluate the use of used tennis balls (TB) as an inert bulking agent. Composting was carried out in an industrial composting plant with a ternary mixture of olive mill waste, the solid fraction of dewatered pig slurry, urban pruning residues, with the addition of TB as a synthetic bulking agent. Composting process parameters, monitored throughout the composting cycle, showed that TB significantly affected the thermal composting process parameters, with increases in operating temperatures, exothermic index, and mineralization of organic matter. Also, compost properties were seen to be of equal or superior quality at the end of the composting with addition of TB. These are the first experimental results testing the effect of a spherical synthetic reutilized product such as TB on composting processes, which was additionally carried out at an industrial scale, showing that using discarded materials such as used tennis balls can improve the efficiency and economy of composting.

Antioxidant and biofertilizing effect of compost extracts on horticultural crops to minimize the use of agrochemicals

Excessive chemical fertilizers harm the environment, economy, and health, while compost and its extracts provide a sustainable solution. Consequently, the development of liquid organic amendments with biofertilizing and antioxidant capabilities is of significant interest in intensive agriculture. To achieve this, four Compost Extraction Protocols (CEP1–4) were applied to different compost to obtain a range of aqueous extracts. These treatments varied in temperature, incubation duration, and agitation. The raw materials for the compost used were Agri-food Waste (AW), Sewage Sludge (SS), Vegetable Waste (VW), and Olive Mill Waste (OMW). The extracts were characterized in physicochemical terms and their potential to promote radicle germination in cucumber and lettuce seeds. Additionally, counts of microbial groups associated with biofertilizing capacity were conducted. Three extracts were chosen based on the germination index to conduct an in vivo bioassay on seedlings. Finally, oxidative stress in radicles and seedlings resulting from the preceding tests was evaluated by quantifying malondialdehyde (MDA), total phenolic compounds (TPC), and ascorbate-glutathione cycle enzymes. The results established that protocols with milder temperatures, such as CEP1 and CEP4, yielded aqueous compost extracts with good biofertilizing and antioxidant properties, although the effect was dependent on crop sensitivity. Specifically, the extracts selected for the seedling trial, OMW-A CEP4, AW-A CEP1, and especially AW-A CEP4, demonstrated a remarkable biofertilizing and antioxidant properties in lettuce, by increasing growth parameters and TPC while decreasing MDA. The results indicate that aqueous compost extracts are a suitable alternative to reduce the consumption of chemical fertilizers.

Accumulation of heavy metals from single and combined olive mill wastewater and pomace in soil and bioaccumulation in tissues of two earthworm species: Endogeic (Aporrectodea trapezoides) and Epigeic (Eisenia fetida).

Soil and earthworms are threatened by anthropogenic contamination resulting from olive mill waste dumping on the soil due to their pollutant properties. While several studies have explored the effects of olive mill waste on soil properties and the accumulation of heavy metals in soil, there is currently a gap in the literature regarding the potential bioaccumulation of heavy metals from olive mill waste in earthworms. In this study, soil with earthworms from two ecological categories (endogeic: Aporrectodea trapezoides and epigeic: Eisenia fetida) was treated with increasing doses of olive mill wastewater (OMWW) and olive mill pomace (OMP), applied individually or combined, in an indoor experiment in plastic containers, under laboratory conditions. The results revealed the presence of significant concentrations of heavy metals in the two types of wastes ranging as follows: Fe˃ Zn˃ Cu˃ Cd˃ Cr for OMWW, and Fe˃ Zn˃ Cu˃ Cr for OMP (with Cd below the detection limit). The study demonstrated distinct effects of OMWW and OMP, both individually and in combination, on soil heavy metal content, ranging as follows: soil OMWW > soil Combination > soil OMP for Cd; soil Combination > soil OMWW > soil OMP for Cr and Fe; and soil Combination > soil OMP > soil OMWW for Cu and Zn. Additionally, our investigation showed that both earthworm species exhibited significant uptake of these metals into their tissues, particularly the endogeic species. Interestingly, the most significant difference between species was in the accumulation of Cu, with the epigeic species accumulating significantly lower amounts.

Purification of olive mill waste: a circular economy model for the Mediterranean region

Purification of olive mill waste: a circular economy model for the Mediterranean region

Simultaneous optimization of activation conditions of alperujo (two-phase olive mill waste) using a desirability function: Production of porous carbons for adsorption and energy storage

Valorization of agro-industrial waste is considered an essential step towards a circular economy. The potential reuse of these byproducts in practical applications requires feasibility assessments and optimization of variables in order to be profitable. In the present study, an abundant and problematic residue from the olive oil industry, “alperujo” (two-phase olive mill waste), was used as precursor material for activated carbons. A simultaneous optimization methodology was applied to maximize two response variables: energy storage capacity and lead (Pb) removal efficiency. The simultaneous optimum conditions were 3.66 g of KOH per g of carbonized residue and a temperature of 650 °C for 120 min. The result was a microporous activated carbon with an energy storage capacity of 252 F/g and a lead removal from aqueous solutions of 68.8 %. These values are comparable with those offered by commercial activated carbons, evidencing that porous materials obtained from alperujo using unique activating conditions for both applications present a remarkable performance. The novelty of the present study lies in the application of a useful statistical methodology for simultaneous optimization through the “desirability function”, resulting in a reduction in cost and time. Our results have demonstrated that it is possible to generate activated carbons with the highest performance for two different applications using the same combination of activation variables.

Comparison of different treatment methods which are used for phenol removal: A mini review

ABSTRACT This article aims to provide a comprehensive overview of the various adsorption methods developed over time for phenol removal. Phenolic substances pose significant threats to aquatic ecosystems, wildlife, and human health. If not properly controlled and treated before discharge, industrial effluents contaminated with phenol can cause detrimental effects on surface and groundwater resources. In comparison with advanced treatments such as ozonation, UV therapy, and the Fenton process, which are associated with higher energy costs, conventional physicochemical treatment methods like adsorption, chemical treatment, membrane filtration, and distillation offer superior removal efficiencies. Pistachio nut shell ash, Moringa peregrina tree shell ash, agricultural fibres, red mud, low-cost clay, olive mill waste, natural zeolites, rubber seed coat, peat, fly ash, and bentonite are just a few examples of the adsorbents and adsorption processes that have been used in literature to remove phenol and its derivatives. For instance, biosorption has been shown to be a successful technique with room for further study in this area regarding regeneration and cost–effectiveness. As a result, numerous researchers in the field of phenolic treatment have emphasized the effectiveness of physicochemical processes over time. Furthermore, additional investigation is required to determine the practical application of inexpensive adsorbents on commercial basis.

Effects of Sustainable Rice Management on the Behavior and Bioefficacy of Bispyribac-Sodium: A Medium-Term Study

The practices (tillage and flooding) used for rice crops are unsustainable, especially in areas characterized by water shortages, such as the Mediterranean region. Therefore, it is necessary to develop sustainable methods in order to ensure the viability of rice production. However, it is essential to understand the effects that alternative management can have on herbicide behavior. In this context, this paper describes the first field experiment conducted to evaluate the medium-term effects of different agricultural practices on the fate of bispyribac sodium (BPS). Thus, the treatments were as follows: tillage and flooding (TF), tillage and sprinkler (TS), and no-tillage and sprinkler (NTS). In addition, “alperujo” compost (AC) from olive mill waste was used in each treatment (TF-AC, TS-AC, and NTS-AC). The AC was applied only once in 2015 when the TS and NTS treatments were implemented. The AC amendment increased the adsorption of BPS and its irreversibility, thereby decreasing the BPS leaching capacity. Furthermore, throughout this study, the BPS persistence was up to 1.85 times greater with sprinklers than in the flooding condition, which could explain the high values of BPS effectiveness (increased by a factor of 1.45 on average) found with sprinklers. Therefore, the implementation of sprinklers in combination with AC can be considered a sustainable strategy for Mediterranean rice production, at least in the medium term, as it reduces BPS water pollution and increases its weed control efficiency.

Improving plant adaptation to soil antimony contamination: the synergistic contribution of arbuscular mycorrhizal fungus and olive mill waste

BackgroundThis study aimed to investigate the alterations in biochemical and physiological responses of oat plants exposed to antimony (Sb) contamination in soil. Specifically, we evaluated the effectiveness of an arbuscular mycorrhizal fungus (AMF) and olive mill waste (OMW) in mitigating the effects of Sb contamination. The soil was treated with a commercial strain of AMF (Rhizophagus irregularis) and OMW (4% w/w) under two different levels of Sb (0 and 1500 mg kg−1 soil).ResultsThe combined treatment (OMW + AMF) enhanced the photosynthetic rate (+ 40%) and chlorophyll a (+ 91%) and chlorophyll b (+ 50%) content under Sb condition, which in turn induced more biomass production (+ 67–78%) compared to the contaminated control plants. More photosynthesis in OMW + AMF-treated plants gives a route for phenylalanine amino acid synthesis (+ 69%), which is used as a precursor for the biosynthesis of secondary metabolites, including flavonoids (+ 110%), polyphenols (+ 26%), and anthocyanins (+ 63%) compared to control plants. More activation of phenylalanine ammonia-lyase (+ 38%) and chalcone synthase (+ 26%) enzymes in OMW + AMF-treated plants under Sb stress indicated the activation of phenylpropanoid pathways in antioxidant metabolites biosynthesis. There was also improved shifting of antioxidant enzyme activities in the ASC/GSH and catalytic pathways in plants in response to OMW + AMF and Sb contamination, remarkably reducing oxidative damage markers.ConclusionsWhile individual applications of OMW and AMF also demonstrated some degree of plant tolerance induction, the combined presence of AMF with OMW supplementation significantly enhanced plant biomass production and adaptability to oxidative stress induced by soil Sb contamination.

The Effect of Varying Olive Mill Wastewater Concentrations on Soil Free-Living Nematode Communities and Lettuce Growth

We assessed the impact of increasing olive mill waste (OMW) concentrations (10%, 35%, 70%, and 100% v/v) on soil free-living nematode communities and Lactuca sativa (lettuce) growth, 10 and 45 days after application (DAA). L. sativa plants showed a survival threshold at OMW10%, with higher concentrations proving fatal. Contrary to expectations, nematode abundance increased with OMW concentration. OMW10% induced a rapid surge in nematode abundance, stabilizing at 45 DAA, resembling control values. OMW35%, OMW70%, and OMW100% plots exhibited persistent, gradual increases, surpassing control values at 45 DAA. All treatments favored fungal feeders, resulting in the overdominance of the genus Aphelenchus both at 10 and 45 DAA. Even though OMW did not exert a toxic effect on nematode populations, this shift in the community structure towards the dominance of a single genus could suggest an imbalance in the soil community, which could have negative implications for soil health and ecosystem functioning. Overall, our study provides insights into the complex interactions between OMW, soil nematode communities, and plant growth, emphasizing the importance of understanding soil ecology for sustainable agricultural management.

Treatment of two-phase olive mill waste and degradation of phenolic compounds with simultaneous bio-electrochemical conversion of CO2 to CH4 using a microbial electrolysis cell

This study deals with the treatment of a two-phase olive mill waste (TPOMW), with simultaneous bio-electrochemical reduction of CO2 to CH4 using a Microbial Electrolysis Cell (MEC). For this purpose, a dual-chamber MEC was constructed using carbon felt as anodic and cathodic electrodes. The performance was assessed in terms of COD removal, the degradation of the phenolic compounds as well as the electromethanosynthesis potential of the MEC bio-cathode. The MEC operated for 120 days and the results showed that increasing the concentration from 3 to 7 and 38 gCOD/L led to an increase of the COD removal from 74%, to 77% and to 87%, respectively, of the total phenolic content removal from 73%, to 76% and to 79%, respectively, as well as of the produced CH4 from 0.04, to 0.09 and to 0.07 mmols/gCODconsumed, respectively. Increasing the applied potential from 0.5 V to 1 V, while the TPOMW was employed in the anode with no dilution, resulted in further increase of both the COD and the total phenolic content removal from 87% to 79%, respectively, to 91%, while the produced CH4 further increased from 0.07 to 0.08 mmols/gCODconsumed. The results indicate that the MEC technology can be potentially exploited for the treatment of the TPOMW and produce CH4 as a waste-to-energy source.

Integrating bioprocess and metagenomics studies to enhance humic acid production from rice straw.

Rice straw burning annually (millions of tons) leads to greenhouse gas emissions, and an alternative solution is producing humic acid with high added-value. This study aimed to examine the influence of a microbial consortium and other additives (chicken manure, urea, olive mill waste, zeolite, and biochar) on the composting process of rice straw and the subsequent production of humic acid. Results showed that among the fungal species, Thermoascus aurantiacus exhibited the most prominent impact in expediting maturation and improving compost quality, and Bacillus subtilis was the most abundant bacterial species based on metagenomics analysis. The highest temperature, C/N ratio reduction, and amount of humic acid production (Respectively in lab 61°C, 54.67%, 298 gkg-1 and in pilot level 65°C, 72.11%, 310gkg-1) were related to treatments containing these microorganisms and other additives except urea. Consequently, T. aurantiacus and B. subtilis can be employed on an industrial scale as compost additives to further elevate quality. Functional analysis showed that the bacterial enzymes in the treatments had the highest metabolic activities, including carbohydrate and amino acid metabolism compared to the control. The maximum enzymatic activities were in the thermophilic phase in treatments which were significantly higher than that in the control. The research emphasizes the importance of identifying and incorporating enzymatically active strains that are suitable for temperature conditions, alongside the native strains in decomposing materials. This strategy significantly improves the composting process and yields high-quality humic acid during the thermophilic phase.

Integral valorization of two-phase olive mill waste: extraction of cellulose and lignin and their characterization

Integral valorization of two-phase olive mill waste: extraction of cellulose and lignin and their characterization