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This study systematically compares the rejuvenation mechanisms and efficacy of waste engine oil bottom (WEOB) residues obtained via distillation and membrane filtration for rejuvenating aged asphalt. A series of experiments—including SARA (saturates, aromatics, resins, and asphaltenes) fractionation, dynamic shear rheometry (DSR), gel permeation chromatography (GPC), and atomic force microscopy (AFM)—were conducted to characterize the chemical composition, rheological properties, molecular weight distribution, and micromorphology of both types of WEOB and the resulting rejuvenated asphalt. The results reveal that the rejuvenation mechanism primarily relies on supplementation and dilution by low-molecular-weight components (saturates and aromatics), coupled with capability for dissolution and dispersion of asphaltene aggregates. Both types of WEOB effectively restored the penetration, softening point, and rheological properties of the aged asphalt, bringing the aged asphalt’s macro-performance and microstructure closer to those of virgin asphalt. Notably, WEOB derived from membrane filtration (MWEOB) demonstrated superior rejuvenation performance compared to distillation-derived WEOB (DWEOB). However, due to the limited capacity of WEOB to dissolve and disperse aged asphaltene aggregates, the recovery of ductility in the rejuvenated asphalt remained suboptimal. These findings provide theoretical support for optimizing process selection and engineering applications of WEOB-based rejuvenating agents.

Automobile emissions have significantly intensified environmental degradation, contributing to climate change. Extensive research is underway to identify alternative fuels that can be renewable and enhance engine efficiency while minimising emissions. This study evaluates the performance and emission characteristics of a diesel engine powered by novel ternary blends of diesel, biodiesel derived from waste cooking oil (WCO), waste plastic oil (WPO), and ethanol (DBE blend). The blends were tested at varying load conditions and cold Exhaust Gas Recirculation (EGR) rates of 7% and 14% on a single-cylinder, 4-stroke, and 3.2 kW power CRDI (Common rail direct injection) diesel engine. Biodiesel was synthesised via a two-step esterification process, meeting ASTM standards. Key findings include improved BTE and reduced emissions with increased ethanol content. The D40CB10E10 blend demonstrates the highest BTE among the biodiesel blends. EGT decreases with rising ethanol content compared to diesel. The D60CB20E20 blend exhibited the lowest NOx emissions (9.98% lower than diesel) and the lowest smoke density. Ethanol’s oxygenation and heat of vaporisation improved combustion, reducing EGT and CO emissions. However, HC emissions increased with ethanol. These results demonstrate that DBE blends can enhance engine efficiency and reduce emissions, offering a sustainable alternative to conventional diesel.

The waste oil emulsion liquid membrane produced by waste oil from oil refineries (WELM) is used to separate the phenol in purified water from the sour water stripper in oil refinery facilities, and the stability of WELM was studied. It is verified that waste refinery oil can be produced into emulsion liquid membrane with good stability and high removal rate for the first time. The WELM stability models were established by response surface methodology (RSM) and artificial neural network (ANN), respectively. The principle and mechanism of various parameters, as well as the interaction effects on the stability of WELM, are proposed. The effects of parameters, including the ratio of Span-80, liquid paraffin, the ratio of internal and oil, and the rotational speed of the homogenizer, were investigated. Under the optimal operating parameters, the WELM had a demulsification percentage of just 0.481%, and the prediction results of RSM and ANN were 0.536% and 0.545%, respectively. Both models demonstrate good predictability. The WELM stability model has a high application value in the treatment of phenol-containing wastewater in the oil refining industry, and provides a green method of resource recovery.

Waste materials such as waste tire rubber (WTR), waste cooking oil (WCO), bio-oils, waste engine oil (WEO), and other waste oils have been the subject of various scientific studies in the sustainable and waste research field. The current environmental concerns have been identified to protect natural resources and reuse waste materials. Accordingly, this work reviews the use of recycled waste tire rubber mixed with waste oils (waste cooking oil, waste engine oil) and bio-oils that can be extracted from waste oils to rejuvenate asphalt in reclaimed pavements. This new solution may reduce the massive amounts of WTR and waste oils and produce a more environmentally sustainable material. Reclaimed, aged asphalt has been rejuvenated to achieve various penetration capabilities and properties by blending asphalt with one or more waste materials to evaluate the binder using standard tests. Many solutions with promising results in improving the properties of asphalt mixtures have been selected for further characterization. This review highlights that the addition of WTR and waste materials to rejuvenated asphalt binders improves stability, enhances the viscoelastic properties, provides better fatigue and crack resistance performance, and enhances the compatibility of the rejuvenated rubber oil asphalt. Moreover, the flashing point, softening point, ductility, and penetration of aged asphalt and Poly(styrene-butadiene-styrene)-rubber-rejuvenated and waste-rubber-oil-rejuvenated asphalt were enhanced after applying the rejuvenator compound. On the other hand, adding waste oil to WTR and asphalt reduces the viscosity and enhances the storage stability compared to the asphalt rubber binder.

The co-pyrolysis of waste lubricating oil and waste cooking oil was carried out with various blend compositions at 450 °C, 3 kW, and 5 min of residence time in a stainless steel reactor. The fraction within the boiling range of diesel fuel, referred to as diesel-like oil, was separated from the pyrolytic oil using ASTM D-86 distillation. Properties of the products were evaluated and compared to the standard properties of petro-diesel as required by ASTM standards and Oil and Gas Regulation Authority (OGRA) standards followed by oil refineries in Pakistan. Results showed that the fraction of diesel-like oil increases, and its final boiling point decreases with the increasing composition of waste cooking oil. It was observed that the maximum yield of pyrolytic oil and a maximum fraction of diesel-like oil were 73 wt.% and 84.5 vol.%, respectively. It was also observed that most of the properties of pyrolytic and diesel-like oils obtained from the blends containing 50% or less waste cooking oil by volume were close to the commercial diesel. This research resulted in converting two environmentally hazardous waste materials in a single facility to produce fuel. The sulfur content of the fuel was lower as compared to the fuel obtained by waste lubricating oil alone, reducing the environmental hazard. The pour point of the fuel was lower than the fuel obtained by waste cooking oil alone, making fuel fit for use in cold weather. This research provided the basis for an economically sound co-pyrolysis facility of waste oils.

As a sustainable management of fossil fuel resources and ecological environment protection, recycling used lubricating oil has received widespread attention. However, large amounts of waste lubricating-oil regeneration wastewater (WLORW) are inevitably produced in the recycling process, and challenges are faced by traditional biological treatment of WLORW. Thus, this study investigated the effectiveness of electrocoagulation (EC) as pretreatment and its removal mechanism. The electrolysis parameters (current density, initial pH, and inter-electrode distance) were considered, and maximal 60.06% of oil removal was achieved at a current density of 15 mA/cm 2 , initial pH of 7, and an inter-electrode distance of 2 cm. The dispersed oil of WLORW was relatively easily removed, and most of the oil removal was contributed by emulsified oil within 5–10 μm. Gas chromatography–mass spectrometry (GC–MS) analysis revealed that effective removal of the biorefractory organic compounds could contribute to the improvement of biodegradability of WLORW. Thus, the 5-day biochemical oxygen demand/chemical oxygen demand ratio (BOD 5 /COD) was significantly enhanced by 4.31 times, which highly benefits future biological treatment. The routes of WLORW removal could be concluded as charge neutralization, adsorption bridging, sweep flocculation, and air flotation. The results demonstrate that EC has potential as an effective pretreatment technology for WLORW biological treatment.

The world is currently strongly emphasizing recycling waste materials and transforming them into useful products. The growing energy consumption and waste production necessitate converting these materials into useful products. In the current research, waste cooking oil (WCO) and waste lubricating oil (WLO) are utilized to produce diesel-like fuel using co-pyrolysis, one of the most effective and environmentally friendly methods. By using co-pyrolysis, two or more waste materials can be converted with a positive synergetic effect in a single facility. Current research is focused on the catalytic co-pyrolysis of WCO and WLO to increase the yield and enhance the properties of pyrolytic fuel as compared to non-catalytic co-pyrolysis. Two catalysts, namely bentonite and kaolin clay, were selected based on their cheapness and availability. A total of nine experiments, four with the bentonite and four with the kaolin clay catalysts, were performed at 5%, 10%, 15%, and 20% of each catalyst by weight. One experiment of non-catalytic co-pyrolysis was also performed for comparison with catalytic ones. All the experiments were performed at 450 °C temperature, 2.4 kW power, 7 minutes residence time, and 1 atm pressure in an inert atmosphere produced by nitrogen gas. The raw materials (WCO and WLO) ratio was 1:1 by weight. The properties of the pyrolytic oil such as API gravity, flash point, cetane number, cloud point, and pour point were evaluated using ASTM standards and compared to standard specifications of commercial diesel fuel. Pyrolytic or co-pyrolytic oils obtained from 20 wt.% of bentonite showed the best results in enhancing yield and improving the properties mentioned above. ASTM D86 distillation of the products was also performed to evaluate the diesel fraction of the products. The maximum yield of 75 wt.% and maximum amount of 87 vol.% diesel fraction was obtained at 20 wt.% bentonite with properties very close to or within the range of ASTM standards for commercial diesel fuel. Graphical Abstract

Vineyard and olive farming are deeply rooted in the economy, culture, and even the welfare of Mediterranean countries. Although numerous approaches and methods were developed to valorize their agricultural residues, several challenges remain to overcome moving towards the Circular Economy (CE). Conventional treatments of winery and olive mill wastes are becoming increasingly expensive, demanding significant amounts of effort, resources, and energy for safe waste discharge. Therefore, the need to recycle, reuse, and recover energy and valuable biocompounds from the wastes of these two sectors become apparent. In the context of increasing waste production, climate change, coupled with dramatic rises in demand from a much larger global population and customers, CE offers the prospect of a better future. Microbes are able to produce diverse biosurfactants (BS) containing both hydrophilic and hydrophobic moieties that could interact with surfaces, lower surface and interfacial tensions, form micelles, and emulsify immiscible substances. Among several BS classes, rhamnolipids are glycolipids produced by some gram-negative bacteria with various potential applications in numerous fields, including bioremediation of contaminated soils. In contrast to several biosurfactants, this particular class of glycolipids is among the economically competitive biomolecules with its synthetic equivalents. For that, we highlighted the main opportunities, the challenges, and the future aspects towards the production of this particular type of glycolipids using winery and olive oil wastes. Therefore, we proposed the critical points that should be assumed through the path of successful strategies for rhamnolipid production using these two potential agricultural residues. This review might help at boosting the current attempts to find novel CE models. Graphic Abstract

This work describes the use of an ultrasound system for the enzymatic transesterification of oils using combi-lipases as biocatalyst. The reactions were carried out evaluating the individual use of waste oil and fresh soybean oil, and the immobilized lipases CALB, TLL, and RML were used as biocatalysts. It was performed in a mixture design of three factors to obtain the ideal mixture of lipases according to the composition of fatty acids present in each oil, and the main reaction variables were optimized. After 18 h of reaction, ultrasound provided a biodiesel yield of about 90% when using soybean oil and 70% using the waste oil. The results showed that ultrasound technology, in combination with the application of enzyme mixtures, known as combi-lipases , and the use of waste oil, could be a promising route to reduce the overall process costs of enzymatic production of biodiesel.

The lubricating oil industry is widespread in the world, but getting rid of the used oils has become an environmental concern. Lubricating oils are used in industries and cars but potentially contaminate groundwater after use. This research uses montmorillonite clay to refine old oil treated with acetic acid. Compared to more conventional procedures, the suggested strategy for treating waste oil is more cost-effective due to the relatively inexpensive cost of the acid and the modest process conditions. Water content, sediment content, density, flash and fire points, viscosity, viscosity index, total acid and base number, pour points, and refractive index were among the physicochemical parameters of the treated oil that were examined as a result of this treatment. We analyzed the oils using Fourier transform infrared spectroscopy (FTIR) and atomic absorption spectrometry (AAS). New oil (10w 40), old oil, oil treated with acetic acid, and montmorillonite clay were all put through their paces in a battery of tests. The therapy’s physical and chemical alterations were examined across all fields. The findings demonstrated the efficiency of montmorillonite clay due to the strength of the acid to separate the sludge and the lack of compounds hazardous to the environment. The process described here enables recycled oil to be reclaimed as base oil.