Quantitative assessment of the valorisation of used cooking oils in 23 countries

Waste Cooking Oils into High-Value Products: Where Is the Industry Going?

Waste cooking oils (WCOs) are generated globally in significant amounts by various sectors including hospitality, households, and industrial operations. Many nations currently lack dedicated legislation for managing WCOs, creating a pressing environmental challenge. At present, WCOs are primarily utilized in industries as raw materials for biodiesel production and energy generation. However, their role in second-generation biodiesel production is contingent on availability, often necessitating imports of either biodiesel or WCOs from other countries. The European Union has emphasized the importance of prioritizing biowaste for high-value alternative products beyond biodiesel to achieve carbon neutrality by 2050. Many reviews have been published in the literature reporting potential WCO applications to produce biolubricants, biosolvents, animal feed, asphalt additives, among others, however, no detailed analysis of industrial trends has ever been presented. Within this panorama, unlike existing reviews that focus on specific polymer classes derived from WCOs, this work sought to present a comprehensive industrial overview of the use of WCOs in creating high-value polymeric materials beyond fuel and energy, providing a general overview of patents published (or alive) in the last 10 years, together with the analysis of which innovative products are being introduced and sold on the market today.

Strategies for the Transformation of Waste Cooking Oils into High-Value Products: A Critical Review

Waste cooking oils (WCOs) are generated globally from households, the hospitality industry, and other sectors. Presently, WCOs are mainly employed as feedstock for biodiesel and energy production, strongly depending on the availability of WCOs, which are often imported from other countries. The objective of this review is to give an overall comprehensive panorama of the impacts, regulations, and restrictions affecting WCOs, and their possible uses for producing high-value products, such as bio lubricants, bio surfactants, polymer additives, road and construction additives, and bio solvents. Interestingly, many reviews are reported in the literature that address the use of WCOs, but a comprehensive review of the topic is missing. Published studies, industry reports, and regulatory documents were examined to identify trends, challenges, production statistics, environmental impacts, current regulations, and uses for high-value polymer production. The data collected show that WCOs hold immense potential as renewable resources for sustainable industrial applications that are in line with global carbon neutrality goals and circular economy principles. However, achieving this shift requires addressing regulatory gaps, enhancing collection systems, and optimizing conversion technologies. This comprehensive review underlines the need for collaborative efforts among policymakers, industry stakeholders, and researchers to maximize the potential of WCOs and contribute to sustainable development.

Sustainable Biocatalytic System for the Enzymatic Epoxidation of Waste Cooking Oil

The present study is integrated in a global effort to capitalize waste cooking oil (WCO) into versatile compounds by introducing an oxirane ring into the unsaturated carbon chain of fatty acid residues (the epoxidation of double bound). Therefore, an enzymatic method was set up for the epoxidation of artificially adulterated WCO (SFw) and WCO under real conditions (SFr) derived from sunflower biomass. Commercial lipase (Novozyme, NZ) was used as a biocatalyst for generating the peracid requested by the epoxidation pathway. Optimum experimental conditions (e.g., 1.5 wt% NZ, 1:1:0.5 = H2O2/double bonds/peracid precursor (molar ratio) and 12 h reaction time) allowed for the conversion of 90% of the SFw substrate into products with an oxirane ring. Octanoic acid was selected as the best peracid precursor. The versatility of the developed system was tested for olive, milk thistle, hemp and linseed oils as both fresh and WCO samples. The characterization of the oil samples before and after the enzymatic epoxidation allowed for the evaluation of the system performance. SFw/SFr exhibited a better susceptibility to enzymatic epoxidation. In addition, the reusability of the biocatalytic system was investigated. Furthermore, different strategies, such as biocatalyst coating and the addition of organic solvents/buffers were applied, limiting enzyme leaching, for the better recovery of the biocatalyst activity.

Production, characterization, and potential applications of lipopeptides in food systems: A comprehensive review

Lipopeptides are a class of lipid-peptide-conjugated compounds with differing structural features. This structural diversity is responsible for their diverse range of biological properties, including antimicrobial, antioxidant, and anti-inflammatory activities. Lipopeptides have been attracting the attention of food scientists due to their potential as food additives and preservatives. This review provides a comprehensive overview of lipopeptides, their production, structural characteristics, and functional properties. First, the classes, chemical features, structure-activity relationships, and sources of lipopeptides are summarized. Then, the gene expression and biosynthesis of lipopeptides in microbial cell factories and strategies to optimize lipopeptide production are discussed. In addition, the main methods of purification and characterization of lipopeptides have been described. Finally, some biological activities of the lipopeptides, especially those relevant to food systems along with their mechanism of action, are critically examined.

Valorization of fat balls and primary scum from wastewater treatment: a promising renewable lipid feedstock for biodiesel production

We investigated the potential of waste materials from wastewater treatment plants (WWTPs) to serve as an alternative lipid feedstock for biodiesel production. The average lipid recoveries from fat balls (46.4%) and primary scum (49.5-54.5%) were higher than the lipid recovery of primary sludge (15.8-16.4%). The yield of biodiesel produced from the extracted lipids ranged from 5.7 to 20.1%. There were considerable site- and season-dependent variations in the characteristics of the lipid waste materials. Radiocarbon analysis indicated the presence of fossil-derived carbon (26.0-42.0%) in the biodiesel obtained from wastewater lipids. Finally, we estimated the potential for biodiesel production from WWTP-derived lipids; about 333.0 metric tons of biodiesel per year could be produced from fat balls and primary scum in Japan. The results indicate that lipid-rich materials from WWTPs represent a valuable alternative feedstock for biodiesel production.

An insight into the utilization of microbial biosurfactants pertaining to their industrial applications in the food sector

Microbial biosurfactants surpass synthetic alternatives due to their biodegradability, minimal toxicity, selective properties, and efficacy across a wide range of environmental conditions. Owing to their remarkable advantages, biosurfactants employability as effective emulsifiers and stabilizers, antimicrobial and antioxidant attributes, rendering them for integration into food preservation, processing, formulations, and packaging. The biosurfactants can also be derived from various types of food wastes. Biosurfactants are harnessed across multiple sectors within the food industry, ranging from condiments (mayonnaise) to baked goods (bread, muffins, loaves, cookies, and dough), and extending into the dairy industry (cheese, yogurt, and fermented milk). Additionally, their impact reaches the beverage industry, poultry feed, seafood products like tuna, as well as meat processing and instant foods, collectively redefining each sector's landscape. This review thoroughly explores the multifaceted utilization of biosurfactants within the food industry as emulsifiers, antimicrobial, antiadhesive, antibiofilm agents, shelf-life enhancers, texture modifiers, and foaming agents.

Potential of Antarctic lipase from Acinetobacter johnsonii Ant12 for treatment of lipid-rich wastewater: screening, production, properties and applications

The present study aimed to screen and optimize lipase production by the Antarctic strain Acinetobacter johnsonii Ant12 for lipid-rich wastewater treatment. Lipase production was successfully enhanced threefold through optimization of culture conditions. The optimum crude lipase activity was observed at 50 °C with high stability in a wide temperature range. The lipase also exhibited high activity and stability in the presence of solvents, metal ions, and surfactants. The crude lipase was used for the treatment of lipid-rich wastewater, which poses a significant challenge, as traditional removal methods are often inefficient or non-eco-friendly. In this study, bioaugmentation with Ant12 resulted in substantial lipid reduction in synthetic as well as real-world wastewater. Multiple linear regression analysis showed that lipid concentration and time were the most significant factors influencing lipid degradation. Bioaugmentation of real-world wastewater with Ant12 cells resulted in 84% removal of lipids in 72 h, while its crude lipase degraded 73.7% of lipids after 24 h. Thus, the specific rate of lipid degradation was higher for crude lipase (0.095/h) than the whole cell treatment (0.031/h). Economic analysis revealed that crude lipase production was much cheaper, faster and more eco-friendly than purified or partially purified lipase production, which justifies its use in wastewater treatment. The high activity of enzyme also implicates its application as a detergent additive. In our knowledge, it is the first study to establish A. johnsonii isolate from Antarctica for lipid-rich wastewater treatment.

Sustainable synthesis of graphene sand composite from waste cooking oil for dye removal

Waste cooking oil (WCO) appears to be a potential carbonaceous source for synthesizing graphene sand composite (GSC) adsorbent in removing pollutants. This study presents a green synthesis method of GSC using WCO as a sustainable carbon source for the synthesis of GSC through the thermal graphitization method. Characterization analysis conducted on GSCWCO verified the successful coating of WCO onto the sand surface and conversion to graphene, which possessed distinct functional groups and features of graphene materials. GSCWCO adsorbent effectiveness in removing Congo Red dye through batch adsorption was studied under the influence of different initial concentrations (20 to 100 mg/L), and the optimum pH (pH 2 to 10), contact time (5 to 240 min), and temperature (25 to 45 °C) were investigated. The GSCWCO showed removal rates of 91.5% achieved at an initial dye concentration of 20 mg L-1, 1.0 g of adsorbent dosage, a temperature of 25 °C, and 150 min of contact time. The GSCWCO exhibited a maximum capacity of 5.52 mg g-1, was well-fitted to the Freundlich isotherm model with an R2 value of 0.989 and had an adsorption mechanism that followed the pseudo-second-order kinetic model. Negative values of enthalpy (ΔH) and Gibbs free energy (ΔG) revealed that CR adsorption onto GSCWCO was a spontaneous and exothermic process. The presence of functional groups on the surface of GSCWCO with such interactions (π-π attractive forces, hydrophobic forces, and hydrogen bonding) was responsible for the anionic dye removal. Regeneration of GSCWCO adsorbent declined after four cycles, possibly due to the chemisorption of dyes with GSC that resulted in inefficient adsorption. Being a waste-to-wealth product, GSCWCO possessed great potential to be used for water treatment and simultaneously benefited the environment through the effort to reduce the excessive discharge of WCO.

Investigation of used cooking oil on the formation of FOG deposits in sewer line clogging

Fat, oil, and grease (FOG) deposits, resulting from saponification reaction, have been identified as the primary source of blockage of sewer pipes. This mainly emanates from the adhesion of these deposits on pipe walls, culminating in the sanitary sewer overflows (SSOs). This undesired phenomenon poses several challenges for municipalities, including environmental issues, health-related hazards, and an increase in incurred costs. Unlike the previous literature, the present study, for the first time, attempts to characterize the effect of used cooking oils (a mixture of different oils) as a perceived crux, triggering the genesis of deposits. The experimental results revealed that there exists a host of physical and chemical disparities between fresh oil calcium soaps (FOCSs) and used oil calcium soaps (UOCSs). Notably, when mixed with water, FOCSs produced non-miscible layers, whereas a homogenous, sticky, and viscous solution observed for UOCSs. Fourier transform infrared (FTIR) analysis casts light on the fact that the heating process would greatly influence the oil chemical structure and its resultant calcium soaps. In comparison with calcium chloride, as time elapsed, the optical microscope images illustrated that the calcium sulfate clots formation proceeded at an accelerated rate, delivering particles with larger sizes. Viscosity and adhesion are two prominent distinctions between soaps. In sharp contrast to soap produced from oil with a higher palmitic acid content, it was discerned that the oil containing less palmitic acid generates UOCSs with higher viscosity and adhesion than FOCSs. It can therefore be inferred that the distinct chemical structures driven by high temperature during the cooking process produce soaps with different characteristics as compared with fresh oil. This phenomenon would have a profound impact on the formation of the deposits in sewer lines.

Optimization and microbial diversity of anaerobic co-digestion of swine manure with waste kitchen oil at high organic loading rates

Anaerobic co-digestion of swine manure (SM) and waste kitchen oil (WKO) was conducted to evaluate the effect of high organic loading rates (OLRs) on biogas production efficiency and microbial changes. Combinations of different loading rates of SM and WKO, with total OLRs from 2 to 8 g VS (volatile solid)/L/d, were evaluated in a laboratory-scale study. While feeding more than 4 g VSSM/L/d did not result in higher biogas production in both mono- and co-digestion scenarios, the addition of WKO increased the total OLR up to 6 g VS/L/d without significant reduction of system productivity. Biogas yields of M2O1 (2 g VSSM/L/d + 1 g VSWKO/L/d) and M4O2 were 910 ± 35 and 849 ± 85 mL/g VSfed which were 25.2 % and 16.9 % higher than the mono-digestion of M2, respectively. A significant increase of bacterial alpha-diversity (Shannon index) was observed in M2O1, at 233.0 ± 3.6 compared with 218.7 ± 5.1 of M2 (p < 0.05). Less bacterial alpha-diversity and accumulation of volatile fatty acids were observed in M4O1 and M4O2, suggesting their potential instability. When digesters were fed with M2, the introduction of 1.4 g VSWKO/L/d or more did not increase biogas yield and could cause system imbalance. The study suggests the limit of WKO could be increased when higher OLRs of SM were applied but should not be more than 4 g VSSM/L/d, and ratio between SM and WKO should be considered to avoid failure. Some of the system disturbances took up to three months to show.

Determination of Maximum Oil Yield, Quality Indicators and Absorbance Spectra of Hulled Sunflower Seeds Oil Extraction under Axial Loading

The present study aims to estimate the maximum oil yield of hulled sunflower seed samples in a uniaxial process under a load of 40 kN and speed of 4 mm/min. The oil samples were assessed for their quality parameters and spectra curves within the wavelength range of 325–600 nm. The results show that heating temperatures in the range of 40 °C to 80 °C increased the oil output; however, a maximum oil yield of 48.869 ± 6.023% with a minimum energy of 533.709 ± 65.644 J at the fifth repeated pressing was obtained from the unheated sample compared to the heated samples. The peroxide values ranged from 6.898 ± 0.144 to 7.290 ± 0.507 meq O₂/kg, acid values from 1.043 ± 0.166 to 1.998 ± 0.276 mg KOH/g oil and free fatty acid values from 0.521 ± 0.083 to 0.999 ± 0.138 mg KOH/g oil, which were within the recommended quality threshold. There were significant spectral differences among the oil samples. A single absorbance peak was observed at 350 nm for all oil samples, indicating low levels of pigment molecules in the oil. The study revealed the need for repeated pressings to recover the considerable residual oil remaining in the seedcake after the first pressing.

Comparative study of the environmental impacts of used cooking oil valorization options in Thailand

Used cooking oil (UCO) is a valuable resource that can be utilized in different ways. Appropriate management of UCO waste can provide environmental and economic benefits, compared to improper disposal practices. This study assessed the environmental impacts of potential UCO valorization options in Thailand. Altogether, 14 scenarios, including 10 for alternative energy recovering processes (S1-10) and other options such as soap production (S11), use in dry pig feed (DPF) production (S12), synthesis of plastics (S13) and polyol (S14), were considered. The defined system boundaries for each scenario include pretreatment, material and energy consumption, and waste treatment stages for the treatment of 1000 kg UCO. Environmental impacts in terms of global warming potential (GWP), freshwater eutrophication potential (FEP), fossil resource scarcity (FRS), and freshwater, terrestrial, and marine eco-toxicity (FE, TE, and ME, respectively) were analyzed using the ReCiPe Midpoint (H) method. The results revealed that all the current waste valorization options create an environmental burden and contribute towards GWP. Scenarios 7 and 10 showed environmental credits for FEP, FE, and ME indicators while scenario 9 did so for FRS. The processes direct energy consumption resulted in the highest contribution to GWP in Scenarios 1, 5-8, 10, 12, and 13. Environmental effects of material consumption and waste treatments were found to be the highest in bio-oil and DPF production, respectively. However, co-products produced could not offset the burden created by energy and material consumption. Overall, the results showed better environmental performance from energy recovery-based UCO management options compared to alternative processes.

Amino Acids Reduce Mild Steel Corrosion in Used Cooking Oils

In this study, we tested several amino acids as eco-friendly inhibitors against corrosion of mild steel by used cooking oils (UCOs). The corrosion inhibition was studied by immersing mild steel rods in the UCOs and reference fresh rapeseed and olive oils mixed with amino acids. The immersion tests were conducted at room temperature for three days. The roles of water and bio-oil preservatives (formic and propionic acids) in the corrosion were explored. The mild steel surface morphology changes after exposure to the oils were analyzed with a scanning electron microscope coupled with an energy dispersive spectroscope (SEM-EDS). The concentration of iron dissolved in the oils was determined with a spectrophotometer. A thick layer was analyzed on the surfaces of the mild steel rods immersed in the oils containing formic or propionic acid and water. This layer provided a minor barrier against corrosion. According to the Fourier transform infrared spectrometer (FTIR) analytical results, the layer consisted of an acid and iron salt mixture. All the tested amino acids decreased the concentration of dissolved iron in the UCOs; particularly, cationic amino acids, L-lycine and L-arginine showed adequate corrosion inhibition properties at low concentrations.

Turning Waste Cooking Oils into Biofuels—Valorization Technologies: A Review

In search of a more sustainable society, humanity has been looking to reduce the environmental impacts caused by its various activities. The energy sector corresponds to one of the most impactful activities since most energies produced come from fossil fuels, such as oil and coal, which are finite resources. Moreover, their inherent processes to convert energy into electricity emit various pollutants, which are responsible for global warming, eutrophication, and acidification of soil and marine environments. Biofuels are one of the alternatives to fossil fuels, and the raw material used for their production includes vegetable oils, wood and agricultural waste, municipal waste, and waste cooking oils (WCOs). The conventional route for WCO valorization is the production of biodiesel, which, as all recovery technologies, presents advantages and disadvantages that must be explored from a technical and economic perspective. Despite its successful use in the production of biodiesel, it should be noticed that there are other approaches to use WCO. Among them, thermochemical technologies can be applied to produce alternative fuels through cracking or hydrocracking, pyrolysis, and gasification processes. For each technology, the best conditions were identified, and finally, projects and companies that work with this type of technology and use WCO were identified.

An appraisal on enablers for enhancement of waste cooking oil-based biodiesel production facilities using the interpretative structural modeling approach

With the continuous depletion of energy sources globally and serious concern regarding environmental degradation by the use of fossil fuel, biodiesel may play a key transponder. Biodiesel blended with diesel fuel achieves a decreased environmental footprint without losing the reliability of output and consumption. Biodiesel is produced from a variety of sources. Biodiesel generation from waste cooking oil (WCO) is effective for both the atmosphere and human health. Many research studies reported WCO biodiesel as a potential alternative fuel for internal combustion engine. The present study aims to provide key promoting and implementing agents for WCO utilization and WCO-based biodiesel production. A systematic literature review has been performed to identify enablers and the contextual relationship between various enablers was developed using interpretative structural modeling (ISM) and expert views. Using the method of ISM and cross-impact matrix multiplication applied to classification (MICMAC) methodology, the impact of enablers is studied. The findings revealed that all established enablers play an important role and are equally important promoters for the development of biodiesel based on WCO. The findings further suggest that human health issues, biodiesel processing plants, biodiesel support vehicles, and biodiesel production technology play a key role in the manufacture of biodiesel dependent on WCO. The most important leaders in the development of WCO biodiesel are government policy and funding, confidence in environmental issues, and financial assistance to biodiesel manufacturers.

Waste Cooking Oil as a Sustainable Bio Modifier for Asphalt Modification: A Review

The rising demand for non-renewable resources such as asphalt binder is a significant issue in the pavement industry. Flexible pavement consumes a significant amount of asphalt binder, which has become a major issue in terms of environmental sustainability and from an economics viewpoint. Hence, researchers strive to find other alternatives to solve these problems, to enhance the performance and lifespan of flexible pavement. Biomass-based bio-oil, such as waste cooking oil (WCO), as a modifier has illustrated favorable effects for asphalt binder and mixture. However, in the pavement industry, its adoption as a modifier is still in an empirical stage. Hence, this paper aimed to give an overview by analyzing literature in-depth to reveal the potential of WCO as a modifier in the pavement industry. The low- and intermediate-temperature performance of the WCO-modified asphalt binder are superior. However, it compromises physical properties and high-temperature performance. Hence, it can be improved by controlling the quality of WCO or by further modification by additives such as ground tire rubber (GTR) and waste plastic. This paper also attempts to review available and potential physical and chemical technologies to minimize the negative effects of free fatty acid (FFA) and water content of WCO on modified asphalt binder properties. For WCO-modified asphalt mixture, the overall performance depends on the dose, quality of WCO, and type of additive added in the WCO-modified binder. Finally, future recommendations are provided to broaden the scope of WCO as a modifier in the forthcoming sustainable pavement industry.

Green chemicals from used cooking oils: Trends, challenges, and opportunities

Food waste reduction is fundamental for sustainable development and pursuing this goal, recycling and the valorization of used cooking oil (UCO) can play a major contribution. Although it has been traditionally used for biofuel production, the oleochemical potential of UCOs is vast. UCOs can be used as feedstock for a large variety of value-added green chemicals including plasticizers, binders, epoxides, surfactants, lubricants, polymers, biomaterials, and different building blocks. Thus, UCO transformation into functional chemicals can bring long-term stability to the supply chain, avoiding the current dependence on commodity products. In this regard, this work describes some of the potential benefits of using UCOs as feedstock in oleochemical biorefineries. In addition, some of the most recent investigations on the valorization of UCOs other than biofuel are presented. Finally, major challenges and future directions are discussed.

Available Technologies and Materials for Waste Cooking Oil Recycling

Recently, the interest in converting waste cooking oils (WCOs) to raw materials has grown exponentially. The driving force of such a trend is mainly represented by the increasing number of WCO applications, combined with the definition, in many countries, of new regulations on waste management. From an industrial perspective, the simple chemical composition of WCOs make them suitable as valuable chemical building blocks, in fuel, materials, and lubricant productions. The sustainability of such applications is sprightly related to proper recycling procedures. In this context, the development of new recycling processes, as well as the optimization of the existing ones, represents a priority for applied chemistry, chemical engineering, and material science. With the aim of providing useful updates to the scientific community involved in vegetable oil processing, the current available technologies for WCO recycling are herein reported, described, and discussed. In detail, two main types of WCO treatments will be considered: chemical transformations, to exploit the chemical functional groups present in the waste for the synthesis of added value products, and physical treatments as extraction, filtration, and distillation procedures. The first part, regarding chemical synthesis, will be connected mostly to the production of fuels. The second part, concerning physical treatments, will focus on bio-lubricant production. Moreover, during the description of filtering procedures, a special focus will be given to the development and applicability of new materials and technologies for WCO treatments.

Improving the recycling technology of waste cooking oils: Chemical fingerprint as tool for non-biodiesel application

Samples of sunflower Waste Cooking Oils (WCOs) subjected to several cycles of frying were treated with water under four different combinations of temperature and pH. Several aspects of the chemical composition of edible, non-treated and processed samples was determined by three different analytic techniques: headspace Solid-Phase Microextraction (HS-SPME) coupled with gas-chromatography (GC), ¹H NMR spectroscopy and ESI-MS spectrometry. Thus, a characteristic chemical fingerprint of each sample was derived and proposed as useful set of tools for the optimization of recycling of WCOs. On the basis of the presented results, a mini-plant for the production of bio-lubricants and bio-solvents with a circular economy approach was designed and herein described.

Used cooking oils as potential oleochemical feedstock for urban biorefineries - Study case in Bogota, Colombia

This work is focused on assessing the potential for the exploitation of used cooking oils (UCOs) as oleochemical feedstock for urban biorefineries. The study case was developed for the city of Bogotá, Colombia. Initially, and according to data from major fats and oils distributors, market information, and public databases, it was estimated that total annual generation of UCOs in Colombia is about 225,000 t, with a per capita of ca. 5 kg/person/yr. Correspondingly, UCOs generation in Bogotá was estimated in at least 45,000 t/yr., with a major generation occurring at Household and HORECA (Hotels, Restaurants and Catering) segments. Specifically in HORECA, fast food restaurants (in particular those of hamburger and chicken) were identified as the main UCOs generators with a suitable supply for industrial exploitation. Then, UCOs samples from this segment of restaurants were subjected to physicochemical characterization by determination of density, volatile matter content, acid value, color, peroxide value, saponification value, iodine value, and content of total polar compounds. The properties associated with the degree of degradation of the oil showed a large variation, even among samples from the same origin. This heterogeneity indicates the need for a pre-treatment process before its reuse. Despite the heterogeneity of the samples, density, iodine value, and saponification value showed slight changes among the different restaurants, largely depending on the nature of the processed cooking oil rather than on the cooking conditions. The collected UCOs showed iodine values and saponification indexes ranging between 80 and 119 g I2/100 g, and 178-201 mg KOH/g, respectively. This indicates that after a suitable purification, UCOs could be used as raw material for a variety of high value oleochemicals. Finally, based upon market data, and to boost further studies, some promissory value-added derivatives are identified.