Search Results (149)

Olive mill wastewaters (OMWWs) are an environmental problem in the Mediterranean region, and it is crucial to explore strategies for their treatment and repurposing. The chemical precipitation technique (CPT) has been presented as a cost-effective wastewater treatment solution that might be applied to OMWW. The CPT-resulting precipitant subproducts (sludge) may be reprocessed (e.g., agricultural fertilizer and/or soil amendment), while the treated wastewater may be repurposed or reused (e.g., irrigation, aquaponic, or industrial processes). This study aimed to evaluate the efficacy of CPT in treating wastewater from the olive oil industry from an ecotoxicological perspective. Additionally, to assess the safe use of the obtained sludge in CPT treatment, its effects on soil biota were assessed. For this, a set of ecotoxicological assays using freshwater (Raphidocelis subcapitata, Daphnia magna and Danio rerio), terrestrial invertebrates (Folsomia candida and Enchytraeus crypticus), and plants (Brassica oleracea and Lolium perenne) were used as model organisms. Results demonstrated that CPT reduced OMWW toxicity to freshwater organisms, offering a favorable outlook on CPT’s potential as a wastewater treatment method. Increasing application rates of sludge in soil reduced the shoot biomass and the hydric content of both plants compared to the control. Survival of F. candida and E. crypticus was not affected by sludge in soil at any tested application rate, yet sludge application negatively affected the reproduction of both species, even at relevant sludge application rates (2%) of sludge in soils. Overall, the applicability of this sludge obtained by the CPT treatment in soils should be carefully evaluated due to the observed adverse effects on soil biota. Although the results of CPT were promising in reducing the toxicity of OMWW for these aquatic species, some adjustments/improvements should be performed to improve this technique and use all the obtained resources (treated water and sludge) in a fully circular perspective. Full article

The olive oil sector constitutes a fundamental pillar in the Mediterranean region from socio-economic and cultural perspectives. Nonetheless, it produces significant amounts of waste, leading to numerous environmental issues. These waste streams contain valuable compounds that can be recovered and utilized as inputs for various applications. This study introduces a novel value chain for olive wastes, focused on extracting lignin from olive pomace by ionic liquids and polyphenols from olive mill wastewater, which are then incorporated as hybrid nanoparticles in the formulation of an innovative starch-based biofertilizer. This biofertilizer, obtained by using residual wastewater as a source of soluble nitrogen, acting at the same time as a plasticizer for the biopolymer, was demonstrated to surpass traditional NPK biofertilizers’ efficiency, allowing for root growth and foliage in drought conditions. In order to recognize the environmental impact due to its production and align it with the technical output, the circularity and environmental performance of the proposed system were innovatively evaluated through a combination of Life Cycle Assessment (LCA) and the Material Circularity Indicator (MCI). LCA results indicated that the initial upcycling process was potentially characterized by significant hot spots, primarily related to energy consumption (>0.70 kWh/kg of water) during the early processing stages. As a result, the LCA score of this preliminary version of the biofertilizer may be higher than that of conventional commercial products, due to reliance on thermal processes for water removal and the substantial contribution (56%) of lignin/polyphenol precursors to the total LCA score. Replacing energy-intensive thermal treatments with more efficient alternatives represents a critical area for improvement. The MCI value of 0.84 indicates limited potential for further enhancement. Full article

Olive mill wastewater (OMW) is a highly polluting effluent rich in organic pollutant compounds derived from olive oil production. In this work, the steam reforming reaction of OMW (OMWSR) was performed in a traditional reactor at 400 °C and different pressures (1–4 bar) to treat and valorize this effluent. A commercial catalyst (Rh/Al₂O₃) was used as a reference sample and several new catalysts were prepared (Ni-Ru/Ce-SiO₂) using different preparation methods to study their effect on the activity and stability. The best-performing catalysts were also subjected to long-term operation experimental tests (24 h). It was observed that the preparation method used for the catalysts synthesis influenced the catalytic performance of the samples. In addition, temperature-programmed oxidation (TPO) analysis of the used catalyst showed the presence of carbon deposits: the results showed that periodic oxidative regeneration improved the catalyst stability and sustained H₂ production. Finally, it was verified that the Ni-Ru/Ce³ catalyst stood out during the experimental tests, exhibiting high catalytic activity along the stability test at 400 °C and 1 bar: H₂ yield always over 7 mol_H2·mol_OMW⁻¹ and total organic carbon (TOC) conversion always higher than 94%. Despite these promising results, further research is needed to assess the economic feasibility of scaling up the process. Additionally, future work could explore the development of catalysts with enhanced resistance to deactivation by carbon deposition. Full article

Olive oil and its derivatives, particularly polyphenol-rich extracts, are valued for their antioxidant, anti-inflammatory, and regenerative properties. Olive mill wastewater (OMWW), a byproduct of olive oil production, traditionally seen as an environmental pollutant, has emerged as a promising source of high-value dermatological ingredients. Key polyphenols such as hydroxytyrosol, oleuropein, and tyrosol exhibit potent antioxidant, anti-inflammatory, antimicrobial, and photoprotective effects. These compounds mitigate oxidative stress, prevent collagen degradation, modulate NF-κB and MAPK signaling, and promote cellular repair and regeneration. Skin health is increasingly recognized as crucial to overall well-being, driving interest in cosmeceuticals that combine cosmetic benefits with dermatological activity. This review examines the cosmeceutical and dermatological potential of OMWW, highlighting its incorporation into innovative topical formulations like oil-in-water nanoemulsions, liposomes, and microneedles that enhance skin penetration and bioavailability. Additionally, OMWW fractions have shown selective antiproliferative effects on melanoma cells, suggesting potential for skin cancer prevention. Valorization of OMWW through biorefinery processes aligns with circular-economy principles, converting agro-industrial waste into sustainable cosmeceutical ingredients. This approach not only meets consumer demand for natural, effective products, but also reduces the ecological footprint of olive oil production, offering a scalable, eco-friendly strategy for next-generation dermatological applications. Full article

Olive mill wastewater (OMW), a byproduct of the olive oil industry, is a potential source of natural bioactive phenolic polymers. In this work, a column chromatography technique was used for the isolation of a new complex polymer (named OMW-2000XAD) from OMW via fractionation on Amberlite^® XAD16 resin. The developed procedure was simple and proved to be reproducible using OMW from two different sources. OMW-2000XAD was further characterized by elemental, glycosidic, and amino acid composition analysis, as well as spectroscopic techniques. The polymer’s molecular size, which was estimated via gel filtration chromatography, was 1960 kDa, which is significantly larger than other high-molecular weight fractions previously isolated from OMW or other agro-industrial wastes. OMW-2000XAD was mainly composed of phenolic compounds (89.8%). It also contained polysaccharides (16.1%) and proteins (10.3%), with glucose (12.25%) and cysteine (1.71%) being the most abundant sugar and amino acid, respectively, as well as metals (1.29%, primarily potassium). However, due to its low solubility, complexity, and heterogeneous composition, it was not possible to identify all phenolic compounds or elucidate a definitive structure via MS, FTIR, and NMR. OMW-2000XAD exhibited strong radical scavenging antioxidant capacity (ABTS^•+, DPPH^• and peroxyl radicals), with results up to 7415 µmol Trolox equivalent/mol (ORAC method), but showed no antiproliferative effects, highlighting the need for further research. Full article

Olive mill wastewater is a by-product of olive oil extraction, characterized by a high concentration of organic matter, which presents a significant environmental challenge if not properly managed. This study was aimed at valorizing olive mill wastewater through selective fermentations to produce acetic beverages with low or no alcohol content. Olive mill wastewaters at three different dilutions (100%, 75% and 50%) were inoculated with Saccharomyces cerevisiae UMCC 855 for alcoholic fermentation. The resulting alcoholic product, with 75% olive mill wastewater, was then used as a substrate for acetic acid fermentation by Acetobacter pasteurianus UMCC 1754, employing both static and submerged acetification systems. The results showed that, at the end of the static acetification process, no residual ethanol was detected and that high concentrations of acetic and gluconic acid (46.85 and 44.87 g/L, respectively) were observed. In the submerged fermentation system, the final ethanol concentration was 24.74 g/L; the produced organic acids content reached 31.63 g/L of acetic acid and 39.90 g/L of gluconic acid. Furthermore, chemical analyses revealed that fermentation enhanced the antioxidant activity of olive mill wastewater. These results suggest promising insights for the valorization of olive mill wastewater. Full article

Recovering oil and water from palm oil mill effluent reduces environmental pollution and promotes sustainable practices. An effective method to achieve this is ultrafiltration (UF), which uses semi-permeable membranes to separate oil, solids, and other contaminants from wastewater under pressure. To assess the most effective recovery method, an experimental comparison was conducted between PVDF and α-Al₂O₃ UF membranes at constant permeate of 20–50 LMH for PVDF and 20–70 LMH for α-Al₂O₃ membranes. Both membranes achieved 99.8% chemical oxygen demand (COD) rejection, with oil concentration factor (F_o) of 186.8% and 253.0%, and water recovery (R_w) of 46.6% and 60.5%, respectively. The permeate water quality was superior to the Malaysian discharge standards, and the fat, oil, and grease (FOG) content was suitable for phase separation processes. The optimal permeate fluxes, with stable transmembrane pressures (TMP), were observed at 40 LMH (PVDF) and 60 LMH (α-Al₂O₃). Total resistance (R_t) values were 1.30 × 10¹² m⁻¹ (PVDF) and 1.59 × 10¹² m⁻¹ (α-Al₂O₃). The ratio of irreversible to total resistances (R_ir/R_t) was 0.02 (PVDF) and 0.06 (α-Al₂O₃), indicating minimal irreversible fouling. Overall, the α-Al₂O₃ membrane demonstrated superior performance in oil and water recovery with more stable operation compared to the PVDF membrane. UF membrane technology emerges as an efficient technique for recovering oil and water compared to conventional methods. Full article

Olive oil production generates vast quantities of by-products, with olive mill wastewater (OMW) being a particularly challenging effluent. Characterized by its dark color, high acidity, and rich composition of organic matter, phenolic compounds, and residual oils, OMW resists conventional degradation methods and poses significant environmental risks due to its phytotoxicity and microbial inhibition. Addressing this issue requires sustainable solutions that align with circular economy principles. A promising strategy involves the biotechnological valorization of OMW using the non-conventional yeast Yarrowia lipolytica, which thrives on organic-rich substrates and converts them into high-value metabolites. This review provides a comprehensive analysis of recent advances in Y. lipolytica applications for OMW valorization, emphasizing its role in developing eco-friendly industrial processes. It begins by outlining the physicochemical challenges of OMW and the metabolic versatility of Y. lipolytica, including its ability to adapt to acidic, phenolic-rich environments. Subsequent sections critically evaluate the yeast’s capacity to synthesize commercially valuable products such as lipases (used in the food and biofuel industries), citric acid (a food and pharmaceutical additive), and polyols like mannitol and erythritol (low-calorie sweeteners). Strategies to optimize microbial productivity, such as substrate pre-treatment, nutrient supplementation, and process engineering, are also discussed. By synthesizing current research, the review highlights how Y. lipolytica-driven OMW valorization can mitigate environmental harm while creating economic opportunities, bridging the gap between waste management and green chemistry. Full article

Untreated olive oil mill wastewater (OOMW) from conventionally farmed olives was used in bread production to create a new functional product. Two types of bread were developed with 50% OOMW (EXP-1) and 100% OOMW (EXP-2) replacing water. Two leavening processes were tested: sourdough inoculum (S) vs. biga-like inoculum (B), with controls (CTR) without OOMW addition. The doughs were monitored throughout the acidification process by measuring pH, total titratable acidity, and the development of key fermentative microorganisms. To assess the hygienic quality during fermentation, plate count techniques were employed. After baking, the breads were evaluated for various quality parameters, including weight loss, specific volume, crumb and crust colors, image analysis, and the presence of spore-forming bacteria. Volatile compounds released from the breads were identified using solid-phase microextraction coupled with gas chromatography–mass spectrometry (SPME-GC/MS). Polyphenolic compounds were analyzed via liquid chromatography–mass spectrometry (LC-MS). To assess the functional properties of the final products, the breads were homogenized with synthetic human saliva and subjected to in vitro digestion. OOMW did not significantly affect the growth of yeasts and lactic acid bacteria (LAB) or the acidification process. However, in terms of the specific volume and alveolation, breads from the S process and OOMW had poor quality, while those from the B process had better quality. Experimental breads (EXP_B-1 and EXP_B-2) contained higher levels of alcohols (especially ethanol and isobutyl alcohol), carbonyl compounds (like benzaldehyde), esters (such as ethyl caproate and ethyl caprylate), and terpenes. OOMW introduced phenolic compounds like hydroxytyrosol, coumaric acid, caffeic acid, and trans-hydroxycinnamic acid, which were absent in CTR_B breads. Functionalization of EXP_B-1 and EXP_B-2 breads was demonstrated by a 2.4- and 3.9-fold increase in Trolox equivalents, respectively. However, OOMW did not reduce post-prandial hyper-glycemia, as starch digestibility was similar between CTR_B and EXP_B breads. The sensory analysis, which focused solely on the visual, structural, and olfactory characteristics of the breads, excluding taste testing to prevent potential health risks from residual pesticides, showed a high appreciation for EXP_B-1 and EXP_B-2 breads, scoring higher than CTR_B in the overall assessment. Full article

Olive mill wastewater (OMW) represents a toxic waste generated during olive oil production (30 million m³/year). Its phytotoxicity and resistance to biodegradation are mainly due to the presence of polyphenols. Methodologies able to remove these organic compounds from this waste to allow the safe dispose of OMW have been developed, and among them, the most effective are oxidation procedures. In this context, we propose an alternative chemical treatment based on the oxidation of OMW using diluted hydrogen peroxide and seleno-organic compounds (diphenyl diselenide and diseleno-bis-benzoic acid) selected as eco-friendly bioinspired catalysts. The effectiveness of the protocol was monitored by Folin–Ciocalteu (F-C) quantification and NMR quantification. The results demonstrated that the greatest reduction in the total phenols content—up to 96%—was achieved using the highest concentrations of catalyst (0.6% _w/w) and oxidant (10% _v/v). Moreover, a toxicological evaluation was carried out using the marine bacteria Aliivibrio fischeri, revealing a significant decrease in toxicity. The EC₅₀ value increased from 0.089 mg/L in the untreated OMW to 18.740 mg/L in the treated sample after removal of the residual catalyst and peroxides. Full article

Palm oil mill effluent (POME), a byproduct of palm oil processing, has substantial resource recovery potential. Its rich biodegradable content supports methane (CH₄) production via anaerobic digestion, enabling renewable energy generation. Additionally, the significant water content of POME can be reclaimed for use in boiler feed, irrigation, and drinking water. However, selecting appropriate technologies to recover valuable resources from POME is challenging, particularly for the purification and upgrading of biogas. Membrane technologies offer an effective approach for transforming POME treatment from an energy-intensive process into a resource recovery system, supporting the decarbonization of palm oil production and advancing global sustainability objectives. This technique is cost-effective and ecofriendly for biogas purification and water reclamation. For biogas purification and upgrading, membrane systems offer the lowest capital and operational costs at 5.654 USD/m³, compared to other technologies, such as 6.249 USD/m³ for water scrubbers and 6.999 USD/m³ for chemical absorbers. This review primarily explores the potential of membranes for gas purification from POME and examines their integration with other processes to develop advanced systems, such as ultrasonicated membrane anaerobic systems and membrane anaerobic systems, to enhance biogas production. In addition, water reclamation from POME is discussed, with ultrafiltration membranes emerging as the most promising candidates. Proton exchange membranes, such as Nafion, are used extensively in microbial fuel cells to improve electricity generation, and this is also summarized. Finally, challenges and future perspectives are highlighted, emphasizing the broader potential of membrane technology in POME wastewater resource recovery. Full article

One of the most persistent and damaging diseases in olive trees is olive knot disease. This disease is caused by an infection by the Gram-negative phytopathogenic bacterium Pseudomonas savastanoi pv. savastanoi that is notoriously difficult to control. The increasing demand for eco-friendly and sustainable agricultural solutions has driven research into plant-based agents. This study investigated the antibacterial properties of essential oils (EOs) and their constituents, olive mill wastewater (OMWW), the phenolic compound hydroxytyrosol (HTyr), and algae and garlic extracts, as well as copper-based and plant-stimulating commercial products against P. savastanoi pv. savastanoi, a significant olive tree pathogen. Antibacterial activity was determined using the Kirby–Bauer disc diffusion and broth microdilution methods. The EOs derived from Thymus vulgaris (thyme) and Origanum compactum (oregano), and their key components thymol and carvacrol, exhibited the strongest antibacterial efficacy. Conversely, the OMWW, plant-stimulating products, and algae and garlic extracts showed limited to no antibacterial activity in vitro, with their antibacterial properties determined using the disc diffusion method. While the EOs were highly effective in vitro, regardless of the testing method, their efficacy in bacterial growth inhibition was strain- and concentration-dependent, possibly highlighting some metabolic or genetic variability in the target pathogen, even though the MIC values against all tested strains of P. savastanoi pv. savastanoi were equal. Bacterial membrane disruption and the consequent leakage of metabolites were determined as the modes of action of carvacrol and oregano EO. Carvacrol also promoted plant growth in lettuce without significant phytotoxic effects, although minor necrotic lesions were observed in young olive leaves at higher concentrations, presenting these agents as potential next-generation green bactericides. Full article

Palm oil mill effluent (POME) is a major contributor to industrial oily wastewater in Malaysia, demanding effective treatment solutions. This study explores the potential of esterified kenaf core (EKC) fiber as an oil adsorbent for oil removal from POME, optimized using a full central composite design (CCD) within the response surface methodology (RSM) framework. The optimum conditions achieved 76% oil removal efficiency, with a 1:0.5 ratio of mercerized kenaf core to stearic acid (MKC:SA), 15 wt% of catalyst, and 1 h reflux time during the esterification process. The regression model exhibited strong predictive capability, with a significant quadratic correlation and an R² value of 0.94. The Fourier transform infrared (FTIR) spectroscopy revealed the existence of ester functional groups characterized by significant hydrophobicity and a decrease in hydroxyl groups, indicating the chemical changes of EKC. Moreover, the scanning electron microscopy (SEM) research demonstrated structural alterations in EKC, including heightened surface roughness, fibrillation, and pore development, which improved oil adhesion relative to raw kenaf core (RKC). These findings indicate that EKC provides an effective, environmentally sustainable solution for managing oil wastewater issues in the palm oil sector, facilitating enhanced ecological sustainability and resource management. Full article

This study aimed to perform an in-depth investigation of olive oil mill wastewater (OOMW). Two OOMW samples (OOMW-A and OOMW-B) from conventionally farmed olives were collected from two different olive oil mills in Palermo province (Italy). Multiresidual analysis indicated that both OOMW samples were unsuitable for food production due to pesticide residues. Specifically, OOMW-A contained 4 active compounds totaling 5.7 μg/L, while OOMW-B had 16 analytes with a total content of 65.8 μg/L. However, polyphenol analysis in the OOMW revealed 23 compounds with high concentrations of hydroxytyrosol, secoiridoid derivatives, phenolic acids, flavones, and total polyphenol content ranging from 377.5 μg/mL (for OOMW-B) to 391.8 μg/mL (for OOMW-A). The microbiological analysis of OOMW samples revealed only detectable viable bacteria (10² CFU/mL) of the lactic acid bacteria (LAB) group. Two distinct LAB strains, Lactiplantibacillus plantarum OMW1 and Leuconostoc mesenteroides OMW23, were identified. These strains demonstrated notable acidification capabilities and produced antibacterial compounds. In conclusion, despite the high polyphenolic content and microbiological suitability of OOMW, the presence of micro-contaminants hinders their use in food production. Thus, further studies are underway to investigate OOMW from organically farmed olives for bakery product functionalization, employing the two selected LAB strains resistant to olive polyphenols as leavening agents. Full article

The increasing global energy demand, coupled with the urgent need to reduce CO₂ emissions, has intensified the search for renewable energy sources. Biogas, produced from agro-industrial biomass, presents a viable solution. In beer production, brewery’s spent grain (BSG), the largest by-product by volume, offers potential for bioenergy recovery. This study applied a biorefinery approach to BSG, extracting protein hydrolysates (PH) through mild alkaline hydrolysis and nanostructured lignin (LN) via the Ionic Liquid Method. The objective was to assess biogas production from the residual biorefinery biomass and evaluate the co-digestion of BSG with Olive Mill Wastewater (OMWW) and Olive Pomace (OP), by-products of the olive oil industry. Biogas was produced in lab-scale batch reactors and the quantity of biogas produced was measured via the volumetric method. Conversely, the amount of biomethane obtained was evaluated by introducing, in the production chain, an alkaline trap. Biogas yields were the highest for untreated BSG (1075.6 mL), co-digested BSG with OMWW (1130.1 mL), and BSG residue after PH extraction (814.9 mL). The concentration of biomethane obtained in the various samples ranged from 54.5 vol % (OMWW + BSG) to 76.59 vol % (BSG). An energy balance analysis considering both the theoretical energy consumed by a semi-continuous anaerobic digestion bioreactor and the energy produced as bio-CH₄ revealed that BSG after PH extraction was the most energy-efficient treatment, producing a net energy gain of 5.36 kJ. For the scope, the energy consumption was calculated by considering a PEIO index equal to 33% of the energy produced during the day, showing the highest biogas production. In contrast, the co-digested BSG with OMWW yielded the lowest net energy gain of 1.96 kJ. This comprehensive analysis highlights the energy efficiency of different treatments, identifying which process should be improved. Full article