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Reusing reclaimed asphalt pavements (RAPs) provides economic, social, and environmental benefits. To improve the performance of these materials, rejuvenating agents such as waste cooking oil (WCO) have been implemented. The annual amounts of RAP and WCO available in the Área Metropolitana de Bucaramanga (AMB) were calculated to be 32 thousand and 22 thousand tons per year, respectively. Subsequently, international standards were reviewed and compared with Colombian regulations to establish a methodology to determine the appropriate percentage of WCO to add to RAP for hot asphalt mix preparation. The authors suggest investigating WCO levels from 3% to 6% and selecting the percentage that reestablishes the penetration grade (INV-E-706-13), softening point (INV-E-712-13), and viscosity (INV-E-717 -13) of asphalt binder. For hot asphalt mix preparation, the authors propose using the Marshall method and determining the appropriate percentage of asphalt according to stability and flow tests (INV-E-748-13), percent air voids (INV-E-736-13), and bulk density (INV-E-733-13).3).

This study presents a take on employing the principles of waste valorization to solve the long-standing problem of finding sustainable resources for biodiesel production. The biodiesel production has always met with a competition with food security and land use. This has limited the scope of the technology to laboratory experiments only. This study aims to assess the geospatial availability of waste cooking oil in Pakistan to map its biodiesel production potential. Owing to the resource posing no land use or food security challenges, a resource assessment using geographical information systems was carried out. The waste cooking oil availability was estimated using the statistics on per capita edible oil consumption with a realistic consumption and collection factor applied to it. The available residual cooking oil was subjected to the transesterification with a rather conservative conversion to the biodiesel at 66.25% to keep the estimates realistic. The study results in heat maps of all the different regions and provinces of the country. The findings suggest that Punjab province is the highest potential province with 249,260 tonnes of biodiesel production annually. Karachi district is the highest potential district with a potential of 36,156 tonnes of biodiesel production in a year. The study paves ways for investment sector in the study area to identify highest potential regions to invest in. It also motivates the scientific community to step outside of experimental research on waste cooking oil’s biodiesel production potential and perform resource assessments and techno-economic analyses on the technology for its widespread adoption. Graphic abstract PS—The callouts do not represent any geographical locations instead they represent the shade of the gradient they correspond to in terms of red being the gradient shade for the problems and the green being the gradient shade for the remedial contributions made by the study. The use of the map of the study area is because of the contextual important of the map in a resource and potential assessment that is geospatial in nature.

Polyhydroxyalkanoate (PHA) is an important bioplastic, its production has been commercialized, and an increase of production capacities is expected. As with many other basic chemicals, PHA production requires a currently unavailable amount of renewable carbon if bioplastic production is ever to compete with plastic production from petroleum. This extensive demand for raw materials poses challenges in terms of costs, logistics, and land use. The application of biogenic residues is therefore one of the prerequisites for any economically significant and environmentally friendly PHA production. Against this background, recent findings on the possibilities of using biogenic residues from food production and consumption to produce PHA are summarized. Waste animal fats, waste cooking oil, but also mixed food waste, either from food production or consumer food waste represent the most abundant food-related residues. They are explored for their potential to serve as substrate for PHA production. While waste animal fat and waste cooking oil can be fed directly into suspension cultures, mixed food waste can be converted into short-chain carboxylic acids from microbial hydrolysis and acidogenesis in dark fermentation before being fed. Titers and productivity of the several feedstock options are compared. The potential for economically viable and sustainable production and integration into local material cycles is highlighted, although there are still several challenges to overcome. Key points • Waste cooking oil enables low-cost and scalable PHA production • Thermally liquefied animal fats are a suitable feed for emulsifier-free PHA production • Coupling dark fermentation and PHA production is economically feasible • The impact of carboxylic acid composition on PHA synthesis is explored

As non-renewable conventional fossil fuel sources are depleting day by day, researchers are continually finding new ways of producing and utilizing alternative, renewable, and reliable fuels. Due to conventional technologies, the environment has been degraded seriously, which profoundly impacts life on earth. To reduce the emissions caused by running the compression ignition engines, waste cooking oil (WCO) biodiesel is one of the best alternative fuels locally available in all parts of the world. Different study results are reviewed with a clear focus on combustion, performance, and emission characteristics, and the impact on engine durability. Moreover, the environmental and economic impacts are also reviewed in this study. When determining the combustion characteristics of WCO biodiesel, the cylinder peak pressure value increases and the heat release rate and ignition delay period decreases. In performance characteristics, brake-specific fuel consumption increases while brake-specific energy consumption, brake power, and torque decrease. WCO biodiesel cuts down the emissions value by 85% due to decreased hydrocarbon, SO2, CO, and smoke emissions in the exhaust that will effectively save the environment. However, CO2 and NOx generally increase when compared to diesel. The overall economic impact of production on the utilization of this resource is also elaborated. The results show that the use of WCO biodiesel is technically, economically, environmentally, and tribologically appropriate for any diesel engine.

A detailed review was conducted to explore waste cooking oil (WCO) as feedstock for biodiesel. The manuscript highlights the impact on health while using used cooking oil and the scope for revenue generation from WCO. Up to a 20% blend with diesel results in less pollutants, and it does not demand more modifications to the engine. Also, this reduces the country’s import bill. Furthermore, it suggests the scope for alternate sustainable income among rural farmers through a circular economy. Various collection strategies are discussed, a SWOC (strength, weakness, opportunity, and challenges) analysis is presented to aid in understanding different countries’ policies regarding the collection of WCO, and a more suitable method for conversion is pronounced. A techno-economic analysis is presented to explore the viability of producing 1 litre of biodiesel. The cost of 1 litre of WCO-based biodiesel is compared with costs Iran and Pakistan, and it is noticed that the difference among them is less than 1%. Life cycle assessment (LCA) is mandatory to reveal the impact of WCO biodiesel on socio-economic and environmental concerns. Including exergy analysis will provide comprehensive information about the production and justification of WCO as a biodiesel.

Background Limonene is an important biologically active natural product widely used in the food, cosmetic, nutraceutical and pharmaceutical industries. However, the low abundance of limonene in plants renders their isolation from plant sources non-economically viable. Therefore, engineering microbes into microbial factories for producing limonene is fast becoming an attractive alternative approach that can overcome the aforementioned bottleneck to meet the needs of industries and make limonene production more sustainable and environmentally friendly. Results In this proof-of-principle study, the oleaginous yeast Yarrowia lipolytica was successfully engineered to produce both d-limonene and l-limonene by introducing the heterologous d-limonene synthase from Citrus limon and l-limonene synthase from Mentha spicata, respectively. However, only 0.124 mg/L d-limonene and 0.126 mg/L l-limonene were produced. To improve the limonene production by the engineered yeast Y. lipolytica strain, ten genes involved in the mevalonate-dependent isoprenoid pathway were overexpressed individually to investigate their effects on limonene titer. Hydroxymethylglutaryl-CoA reductase (HMGR) was found to be the key rate-limiting enzyme in the mevalonate (MVA) pathway for the improving limonene synthesis in Y. lipolytica. Through the overexpression of HMGR gene, the titers of d-limonene and l-limonene were increased to 0.256 mg/L and 0.316 mg/L, respectively. Subsequently, the fermentation conditions were optimized to maximize limonene production by the engineered Y. lipolytica strains from glucose, and the final titers of d-limonene and l-limonene were improved to 2.369 mg/L and 2.471 mg/L, respectively. Furthermore, fed-batch fermentation of the engineered strains Po1g KdHR and Po1g KlHR was used to enhance limonene production in shake flasks and the titers achieved for d-limonene and l-limonene were 11.705 mg/L (0.443 mg/g) and 11.088 mg/L (0.385 mg/g), respectively. Finally, the potential of using waste cooking oil as a carbon source for limonene biosynthesis from the engineered Y. lipolytica strains was investigated. We showed that d-limonene and l-limonene were successfully produced at the respective titers of 2.514 mg/L and 2.723 mg/L under the optimal cultivation condition, where 70% of waste cooking oil was added as the carbon source, representing a 20-fold increase in limonene titer compared to that before strain and fermentation optimization. Conclusions This study represents the first report on the development of a new and efficient process to convert waste cooking oil into d-limonene and l-limonene by exploiting metabolically engineered Y. lipolytica strains for fermentation. The results obtained in this study lay the foundation for more future applications of Y. lipolytica in converting waste cooking oil into various industrially valuable products.

The increasing generation of waste cooking oil (WCO) poses significant environmental challenges, making its valorization essential for sustainable waste management. This research investigates the in situ peracid method for epoxidizing a hybrid mixture of oleic acid and waste cooking oil. A novel approach is proposed by utilizing hybrid raw materials in the presence of natural zeolite as a catalyst to enhance epoxidation efficiency. The signal-to-noise (S/N) ratio analysis in Taguchi method showed that the optimum process parameters for production of epoxidized hybrid oleic acid and waste cooking oil to the response of relative conversion to oxirane (RCO) with determination of oxirane oxygen content (OOC) was maximum (50%) under following conditions: temperature of 50 °C, stirring at 100 rpm, and a molar ratio 1:1 with formic acid. After 100 iterations, the reaction rate constant based on optimized epoxidized hybrid oleic acid and waste cooking oil production was obtained as follows: k 11  = 13.45 mol⋅L −1 ⋅min −1 , k 12  = 14.08 mol⋅L −1 ⋅min −1 , k 2  = 0.023 mol⋅L −1 ⋅min −1 , and k 3  = 0.025 mol⋅L −1 ⋅min −1 .This discovery helps reduce waste, turns used cooking oil into a valuable commodity, and offers insight into reaction kinetics, a critical concept for industrial applications that is environmentally friendly.

Mesoporous, bifunctional MgO-SnO 2 nanocatalysts with enhanced surface area are used for producing biodiesel from waste cooking oil. Biodiesel with yield of 80% is achieved within the first 20 min when transesterification is carried out at an optimum condition of 18:1 methanol to oil ratio, 2 wt% of nanocatalyst, and at a reaction temperature of 60 °C. The conversion gives a maximum yield of 88% when transesterification is allowed to continue for 120 min. The waste cooking oil used in this work is dominated with linoleic acid and oleic acid, which during transesterification gets converted into methyl linoleate and 9-octadecenoic acid methyl ester. These nanocatalysts are fabricated using a composite of rutile (tetragonal) phase SnO 2 and cubic phase MgO nanostructures with prominent crystal orientation along [211] and [200] plane respectively. The MgO-SnO 2 nanocomposites with an enhanced surface area of 31 m 2 /g, basic sites of 2 mmol/g, and particle size of ~15 nm are synthesized by novel sequential thermal decomposition and sol-gel technique. The synthesized wide band gap nanocomposites have Mg and Sn in the ratio of 15:1 and do not have any impurity phases as observed in the X-ray diffraction pattern and EDS spectrum. The presence of surface oxygen states and Mg 2+ and Sn 4+ oxidative states is responsible for the catalytic activity and recyclability displayed by the composites. This work signifies the role of nanocomposites and their synthesis conditions in improving the rate of transesterification. These metal oxide nanocomposites which are nontoxic, stable, cost effective, and easier to synthesis are promising catalysts for large-scale transesterification of waste cooking oil to biodiesel.

In this paper, Pseudomonas aeruginosa MTCC7815, a biosurfactant producing strain was studied for its ability to utilize waste cooking oil (WCO) as a sole carbon source for the production of biosurfactant. Culture conditions were optimized based on surface tension reduction and biomass concentration. The obtained biosurfactant was characterized using 1H NMR, FTIR, LC–MS, and MALDI-TOF techniques. The chemical properties of the produced biosurfactant were estimated by assessing the critical micelle concentration (CMC), emulsification index (E24) and oil displacement test. The optimal culture conditions were found to be similar to the natural domestic sewage such as basic pH value of 10, temperature of 25 °C and a very high WCO concentration of 40 gL−1 (C/N ratio of 40/1). The biosurfactant yield was found to be significant as 11 ± 0.2 gL−1 upon utilizing about 90% of WCO within 5 days of incubation. The biosurfactant produced was found to be a mixture of mono- and di-rhamnolipid in nature and comprised excellent surface active properties i.e. an extremely low CMC of 8.8 ± 0.3 mgL−1, E24 of 62.5 ± 0.3% and surface tension reduction up to 26.2 ± 0.5 mNm−1. These results suggest the suitability of Pseudomonas aeruginosa for the biosurfactant production at commercial scale along with waste remediation in an economic way.

As the demand for sustainable energy sources intensifies, biodiesel emerges as a compelling renewable alternative to petroleum-based fuels. Leveraging waste cooking oil (WCO) as a feedstock not only offers an environmentally friendly fuel source but also addresses waste disposal issues. However, biodiesel production from WCO faces challenges, particularly due to its high free fatty acid (FFA) content, which can hinder efficient conversion and lead to soap formation in traditional alkaline-catalysed processes. This study seeks to overcome these challenges by developing and optimizing a bifunctional Ce/Mn(10:90)/γ-Al₂O₃ catalyst via the incipient wetness impregnation (IWI) method. The catalyst’s dual acidic and basic active sites enable simultaneous esterification and transesterification, enhancing biodiesel production efficiency from high-FFA feedstocks. Various parameters were optimized, including calcination temperatures, catalyst loadings, and reaction conditions such as methanol-to-oil ratio, catalyst loading, reaction temperature, and time for the transesterification process. The Ce/Mn(10:90)/γ-Al₂O₃ catalyst, calcined at 800 °C, achieved a maximum triglyceride (TG) conversion of 97% under optimal conditions. These conditions were determined to be 10 wt% catalyst loading, a 1:24 methanol-to-oil ratio, a reaction temperature of 65 °C, and a reaction time of 3 h. The catalyst’s high efficiency is attributed to its high basicity (1.543 mmol/g), large surface area (143 m 2 /g), and small particle size (22 nm), which collectively enhance its catalytic performance. This bifunctional catalyst design thus offers a robust solution for the efficient conversion of high-FFA WCO into biodiesel, maximizing performance and sustainability.