European Standardization Committee Research Articles

Biofilms, mobile genetic elements and the persistence of pathogens on environmental surfaces in healthcare and food processing environments.

Biofilms are the natural state for bacterial and fungal species. To achieve surface hygiene in commercial facilities, the presence of biofilms must be adequately considered. However, standard disinfectant and sanitizer efficacy tests required by the US-EPA and the European Committee for Standardization (CEN) do not currently consider the role of environmental biofilms. This selective review will discuss what biofilms are and why they are important. We will also cover where they are commonly found in healthcare and food processing facilities and explore how current antimicrobial test methods required for product registration do not test for the presence of biofilms. Additionally, we will explore how a lack of efficacy against biofilms may play a role in the development of antimicrobial resistance in healthcare facilities due to the exchange of mobile genetic elements that occur readily in a biofilm matrix.

Obtaining accurate population estimates with reduced workload and lower fish mortality in multi-mesh gillnet sampling of a large pre-alpine lake.

The EU Water Framework Directive requires monitoring of the ecological status of lakes, with fish as a relevant class of biotic quality indicator, but monitoring fish populations in large lakes is demanding. This study evaluated use in Lake Constance of a novel multi-mesh gillnet modified to reduce catch numbers. In direct comparison with conventional European Committee for Standardization (CEN) nets we achieved 48% reduction in fish mortality with 38% less labour for tasks directly influenced by fish catch numbers, while maintaining comparable species composition and catch per unit effort. Comparison of mesh sizes indicated no significant reduction in species detection in area-reduced panels of the small mesh sizes, while total observed species richness was greater when using the modified nets. Differences in benthic species communities among depth strata were common, while those of pelagic zones were more homogeneous and did not differ significantly with depth. Catches of different net types from the same depth stratum did not exhibit significant differences. The dominance structure of the most common species, relevant to lake assessment, was similar in catches of both net types, suggesting overall superiority of the modified nets in Lake Constance. Sampling conducted according to standard European CEN protocol, while deploying 60% fewer nets, yielded sufficiently precise abundance estimates for monitoring shallow areas of the benthic zone. A 50% difference in the abundance of dominant species was detected among sampling events with a certainty of 95%. The sample did not provide comparable accuracy in deep benthic strata or the pelagic zone, but was adequate to record complete inventories of species present. Based on this trial data, a new stratified sampling design is proposed for monitoring large lake fish communities for ecological assessment. Depth-dependent fish communities were used to calculate the required number of nets, which resulted in a 69% reduction for the entire lake compared to the CEN calculation method. Using the modified nets increases the feasibility of performing WFD surveys, by reducing effort and cost, while the simultaneous halving of fish mortality minimises the negative impact of fish surveys.

Development of South Africa Macadamia Nuts and its Utilization for Biodiesel Production

Demands for energy are rising as the world's population expands. To meet these demands, fossil fuels have been overused, yet this over reliance on them has led to their depletion. The usage of fossil fuels has also significantly contributed to the release of greenhouse gases, which is a serious environmental concern. Sustainable energy is therefore environmentally friendly and financially sound. Petro-diesel can be replaced by biodiesel because it is biodegradable and less hazardous. Biofuel is any fuel produced from biomass, which can be either animal fats or waste, plant or algae material as a feedstock. Biomass benefits in producing fuels which helps to lessen the demand for petroleum fuel and products. Petroleum fuel and gas increase the greenhouse gas emissions profile of the transportation sector. The Republic of South Africa (RSA) is the 14th world's largest emitter of greenhouse gases. This is due to the emissions resulting from burning and heavy reliance on coal. Since biofuel can be produced domestically from natural sources like soybeans, rapeseed, macadamia nuts, coconuts, and even leftover cooking, it has the potential to serve as a remarkable substitute for the commonly used petroleum-derived diesel fuel. This study addresses the historical development of macadamia nuts with a focus on the South African Macadamia Nuts (SAMN) industry, its origin, and as a feedstock for biodiesel production. The generation and classification of biodiesel, physicochemical properties, biodiesel standards, and both American Society for Testing and Materials (ASTM), European Committee for Standardization (EN 14214), and South African biodiesel framework standards are discussed. Furthermore, the biodiesel blending requirements, techniques, and benefits were outlined. Finally, the biodiesel regulatory framework of SA and biodiesel framework as per the Biodiesel Task team (BTT) was examined.

Refuse-derived fuel (RDF) production and analysis in mechanical-biological treatment (MBT) plant from the municipal solid waste

This study reports on the potential of refuse-derived fuels (RDF), which are produced from Sulaimani Municipal solid waste (MSW) using a biodrying process. Plastic, organic wastes, iron materials, and textiles were used in the formulation of RDF samples. A sample of raw MSW material was collected comprising of 40.6% organic, 29.3% plastic, 6.3% Textiles, 5.1% paper, 3.1% wood, 4.6% glass and stone, 5.2% iron containing materials, and 1.3% others. Physical and chemical properties of the RDF were investigated, including its moisture, ash, total chlorine, and heavy metal content with, calorific value. Based on the experimental results, RDF produced from MSW can be classified into net calorific and total chlorine content values NCV 2 and Cl 4 respectively. In accordance with the European Committee for Standardization (CEN standard), the results of this preliminary investigation of RDF samples made from non-biodegradable and non-recyclable MSW fractions, is necessary to analyze a larger pool of samples in order to project appropriate RDF energy-recovery-enhancing composition.

Natural resistance of coppiced and non-coppiced rosewood (Pterocarpus erinaceus Poir.) under outdoor field exposure to termites

ABSTRACT Pterocarpus erinaceus, sourced from natural stands, is famed for producing naturally durable heartwood for several outdoor wood products, which has contributed to overharvesting and threats of extinction. The species coppices could offer essential strategy in curbing timber over-exploitation towards sustainable management. This study aimed to establish confidence in utilizing the coppiced wood in accordance with the EN 252 standard (European Committee for Standardization). Mass loss of wood specimens and appearance grading were used to evaluate termite resistance within the coppiced and non-coppiced stems. Mass loss due to termites was much lower in heartwood than in sapwood, this was true for wood coming from the non-coppiced and coppiced stands. It generally decreased from the butt to the top/crown of both trees. Heartwood and sapwood along each tree species would be highly and moderately resistant against termite attack respectively. Due to their high durability, the rosewood trees would be suitable for engineering applications. Thus the promotion of the coppiced P. erinaceus wood production would supplement the use of its non-coppiced counterpart to increase the wood market base.

LHYMO: A new Water Framework Directive‐compliant multimetric index to assess lake hydromorphology and its application to French lakes

Abstract Hydromorphology provides a physical framework for aquatic biocenoses. Its condition directly affects the quality of habitats available for fauna and flora, and its assessment is therefore useful for biodiversity and water quality conservation, as well as for restoration programmes required by European and national directives. In this study, a site‐specific index of Lake HYdroMOrphology, LHYMO, was developed to provide a quantitative assessment of the hydromorphological status of natural and non‐natural lakes that is consistent with European Committee for Standardization (CEN) standards and that can be used for different purposes, including the implementation of the Water Framework Directive (WFD) and of the Habitats Directive. This new LHYMO index includes nine metrics related to the morphological WFD quality elements (QEs) and six metrics related to the hydrological WFD QEs, all of which are considered to support biological elements. The reference conditions were defined for each metric using an original approach: the degree of alteration is measured in relation to the natural characteristics of each lake, relative to a state that ‘would be expected in the absence of disturbances’. Besides its use for regulatory purposes, this index is also a suitable tool for monitoring the efficacy of hydromorphological restoration projects or to help target effective conservation measures on lakes. Application of this index to 72 French lakes provides the first quantitative and homogeneous assessment of the hydromorphological quality of lakes over a whole territory and gives the first overview of the hydromorphological status of lakes in France, with classification into five classes ranging from ‘high’ to ‘bad’. LHYMO is already operational for large French lakes as it relies mostly on reference datasets available at a national scale, and it may also be used in a wider scope through gathering or completing data from other sources.

Hydrodynamic Cavitation Reactor for Efficient Biodiesel Production. A Review

Biodiesel emerges as a viable option to replace fossil fuels, but the traditional process for the production of biodiesel requires a large energy expenditure, since transesterification has a slow conversion due to the immiscibility of alcohol and oil. On the other hand, with the hydrodynamic cavitation method, a shorter conversion time can be achieved with a high yield; however, there are few studies related to this method. Therefore, the objective of this article is to analyze information from different scientific publications to compare and visualize the parameters used to obtain biodiesel by means of a hydrodynamic cavitation reactor. For this reason, a bibliometric analysis and a systematic review based on the PRISMA method were carried out. In this sense, the relevant articles were selected from the Web of Science, Scopus and Google Scholar databases published between January 2018 and July 2023.Finally, the values of biodiesel yield efficiency were obtained by analyzing the different operating parameters and the different feedstock sources for its elaboration in the hydrodynamic cavitation reactors and comparing their results with international standards. American Society for Testing and Materials (ASTM) D6751 y European Committee for Standardization(EN)14214. It is concluded that hydrodynamic cavitation produces biodiesel that meets international standards and that the highest yields in biodiesel production in most studies have temperature ranges between 50 to 65°C, alcohol: oil molar ratio of 6:1, and methanol is the most used in tranasesterification.

Towards standardized guidelines in digital data acquisition for monitoring and maintenance of European transport infrastructures

AbstractThe digital transformation of the architecture, engineering, and construction sector is associated with an enormous production of data. The appearance of new technologies is leading the way for more sustainable and interconnected infrastructures. Therefore, data analytics is crucial to know the current state of infrastructure and will help towards the efficient management of assets. The main issue is how to collect and exploit meaningful data throughout the lifecycle of infrastructure assets to further allow human experts and computers to make accurate diagnostics, predictions, and decisions. This contribution presents the insights gained in the course of IM‐SAFE project, showing the strategy followed to create guidelines for data collection to monitor and maintain critical assets in the infrastructure network (bridges and tunnels). It tackled a variety of surveying technologies, from destructive and non‐destructive, to chemical methods, among others. The results obtained will support the European Committee for Standardization (CEN) in the standards for monitoring and maintenance of bridges and tunnels, accelerating the adoption of new standards by public authorities and stakeholders in transport infrastructure.

In-house validation of an LC-MS method for the multiplexed quantitative determination of total allergenic food in chocolate.

Mass spectrometry has been widely accepted as a confirmatory tool for the sensitive detection of undeclared presence of allergenic ingredients. Multiple methods have been developed so far, achieving different levels of sensitivity and robustness, still lacking harmonization of the analytical validation and impairing comparability of results. In this investigation, a quantitative method has been validated in-house for the determination of six allergenic ingredients (cow's milk, hen's egg, peanut, soybean, hazelnut, and almond) in a chocolate-based matrix. The latter has been produced in a food pilot plant to provide a real and well-characterized matrix for proper assessment of method performance characteristics according to official guidelines. In particular, recent considerations issued by the European Committee for Standardization have been followed to guide a rigorous single-laboratory validation and to feature the main method performance, such as selectivity, linearity, and sensitivity. Synthetic surrogates of the peptide markers have been used both in native and labelled forms in matrix-matched calibration curves as external calibrants and internal standards, respectively. A two-order of magnitude range was investigated, focusing on the low concentration range for proper assessment of the detection and quantification limits (LOD and LOQ) by rigorous calibration approach. Conversion factors for all six allergenic ingredients have been determined for the first time to report the final quantitative information as fraction of total allergenic food protein (TAFP) per mass of food (µgTAFP/gfood), since such areporting unit isexploitable in allergenic risk assessment plans. The method achieved good sensitivity with LOD values ranging between 0.08 and 0.2 µgTAFP/gfood, for all ingredients besides egg and soybean, whose quantitative markers reported a slightly higher limit (1.1 and 1.2 µgTAFP/gfood, respectively). Different samples of chocolate bar incurred at four defined concentration levels close to the currently available threshold doses have been analyzed to test the quantitative performance of the analytical method, with a proper estimate of the measurement uncertainty from different sources of variability. The sensitivity achieved resulted in compliance with the various threshold doses issued or recommended worldwide.

Machine Grading of High-Density Hardwoods (Southern Blue Gum) from Tensile Testing

Hardwoods commonly have high mechanical properties, which makes them interesting for structural use, but softwoods dominate the structural timber market in Europe. Tensile strength classes are recommended for engineered wood products. However, current European standards do not provide tensile strength classes for hardwoods and the declaration of tensile properties from machine grading in the industry is not yet possible. The present paper aims to contribute to the revision of European standards through the technical group CEN/TC124/WG2/TG2: Tensile strength classes for hardwoods, of the European Standardisation Committee. An experimental campaign which involved machine grading and tensile testing of over 569 boards of Southern blue gum (Eucalyptus globulus Labill.) from Spain and Portugal was made. Six new tensile strength classes were defined, from ET24 (ft,0,k = 24 N/mm2, Et,0,m = 18 kN/mm2 and ρk = 590 kg/m3) to ET42 (ft,0,k = 42 N/mm2, Et,0,m = 23 kN/mm2 and ρk = 640 kg/m3). Machine grading made possible the definition of six strength class combinations. Four combinations resulted in 40% of the sample being assigned to the higher strength class, with low percentages of rejection (varying between 1% and 14%). This demonstrates the high mechanical properties of the species and the performance improvement of machine grading with respect to current visual grading.

Fire resistance of pine wood treated with phenol-formaldehyde resin and phosphate-based flame retardant

ABSTRACT Wood is a commonly used material in construction. However, its application is limited due to its flammability. Modification of wood with phenol-formaldehyde resin (PF) can improve many of its inherent properties, but does not upgrade its fire resistance. To address this issue, Scots pine (Pinus sylvestris L.) sapwood was impregnated with a low molecular weight PF resin and phosphate-based flame retardant (FR). The fixation of the FR was evaluated using an accelerated ageing procedureaccording to the EN 84 standard (CEN 2020: EN 84 (2020) Wood Preservatives – Accelerated Ageing of Treated Wood Prior to Biological Testing - Leaching Procedure (Brussels, Belgium: European Committee for Standardization)). The thermal stability, flammability and heat release of treated wood were analysed before and after a leaching test. The combination of PF and FR treatment significantly improved the thermal stability, reduced flammability and decreased the heat release, as evidenced by a 82% and 86% reduction in total heat release within 600 s compared to untreated wood and pure PF-treated wood, respectively. The improved fire performance was also observed for the leached wood.

Rapid spilled oil analysis using direct analysis in real time time-of-flight mass spectrometry

BackgroundThe biomarker diagnostic ratio analysis outlined by the European Committee for Standardization is considered the current gold standard in oil forensic analysis. However, it has a major limitation as an emergency response procedure in the case of a large scale oil spill due to the high number of samples collected, long GC/MS instrument run time, and the time-consuming data processing required. This current study utilized direct analysis in real time time-of-flight mass spectrometry to develop a rapid spilled oil screening method. An exploratory search of biomarkers and synthetic additives was conducted on reference oil samples of various types. To build a robust yet swift procedure for oil typing, specific heat maps were built with extensive reference sample modelling. These heat maps were then used to select relevant ions from which principal component analysis and discriminant analysis of principal component models were constructed to result in defensible oil classifications.ResultsThe initial exploratory search of biomarkers and additives in the various reference oil samples resulted in promising preliminary matches. The heat map and multivariate statistical analysis oil typing method was applied to three unknown samples, all of which were classified accurately.ConclusionThe merit of direct analysis in real time time-of-flight mass spectrometry on oil forensic was confirmed with the detected biomarkers compound class starting members and lubricating additives along with the successful application of heat maps and multivariate statistical analysis, providing a swift yet reliable screening tool for oil spill environmental monitoring and impact surveying.

Enhancement of oil forensic methodology through the addition of polycyclic aromatic nitrogen heterocycle biomarkers for diagnostic ratios

Current oil spill forensic identification of source oils relies upon hydrocarbon biomarkers resistant to weathering. This international technique was developed by the European Committee for Standardization (CEN), under EN 15522–2 Oil Spill Identification guidelines. The number of biomarkers have expanded at pace with technological advances, while distinguishing new biomarkers becomes more challenging due to interference of isobaric compounds, matrix effects, and high cost of weathering experiments. Application of high-resolution mass spectrometry enabled exploration of potential polycyclic aromatic nitrogen heterocycle (PANH) oil biomarkers. The instrumentation showed reduction in isobaric and matrix interferences, allowing for identification of low-level PANH and alkylated PANHs (APANHs). Weathered oil samples, obtained from a marine microcosm weathering experiment, enabled comparison with source oils to identify new, stable forensic biomarkers. This study highlighted eight new APANH diagnostic ratios that expanded the biomarker suite, increasing the confidence for identifying highly weathered oils back to their source oil.

What Makes a Quality Health App? Developing a Global Research-based Health App Quality Assessment Framework for CEN-ISO/TS 82304-2: A Delphi Study.

The lack of an international standard for assessing and communicating health app quality and even of consensus about what makes a high-quality health app negatively affects uptake of such apps. At the request of the European Commission, international Standard Development Organizations (SDOs) CEN-CENELEC, ISO, and IEC have joined forces to develop a Technical Specification (TS) for assessing the quality and reliability of health and wellness apps. This study aimed to create a useful, globally applicable, trustworthy, and usable framework to assess health app quality. A two-round Delphi technique with 83 experts from 6 continents (predominantly Europe) participating in one (n=42) or both (n=41) rounds was used to achieve consensus on a framework for assessing health app quality. Aims included identifying the at most 100 requirement questions for uptake of health apps that do or do not qualify as medical devices. The draft assessment framework was built on 26 existing frameworks, the principles of stringent legislation, and input from 20 core experts. A follow-up survey with 28 respondents informed a scoring mechanism for the questions. After subsequent alignment with related standards, the quality assessment framework was tested and fine-tuned with manufacturers of 11 COVID-19 symptom apps. National mirror committees from the 52 countries spanning 6 continents who participated in the SDO technical committees, were invited to comment on 4 working drafts and afterwards vote on the TS. The final quality assessment framework includes 81 questions, 67 of which impact the scores of 4 overarching quality aspects. After testing with people with low health literacy, these aspects were phrased as 'Healthy and safe', 'Easy to use', 'Secure data', and 'Robust build'. The scoring mechanism enables communication of the quality assessment results in a health app quality score and label, alongside a detailed report. Unstructured interviews with stakeholders revealed that evidence and third-party assessment are needed for health app uptake. The manufacturers considered the time needed to complete the assessment and gather evidence (2 to 4 days) acceptable. Publication of CEN-ISO/TS 82304-2:2021 Health software - Part 2: Health and wellness apps - Quality and reliability was approved in May 2021 in a nearly unanimous vote by 34 national SDOs from 6 continents. These included 6 of the 10 most populous countries worldwide (China, India, the US, Pakistan, Brazil, and Russian Federation). A useful and usable international standard for health app quality assessment was developed. Its quality, approval rate, and early use provide proof of its potential to become the trusted, commonly used global framework. The framework will help manufacturers to enhance and efficiently demonstrate the quality of health apps, consumers and healthcare professionals to make informed decisions on health apps, and insurers to make reimbursement decisions on health apps.

Biomarkers Profile of the Mysterious 2019 Oil Spill on the Northeast Coast of Brazil and Discrimination from Unreported Events

In 2019, large amounts of oil reached the northeast coast of Brazil, causing damage to the environment and the local economy, especially in the state of Pernambuco. In order to correlate with possible sources, investigation was made of the geochemical biomarkers of the oils using “gold standard” forensic protocols from the European Committee for Standardization (CEN). The biomarkers study was improved by using gas chromatography-tandem mass spectrometry (GC-MS/MS), rather than the standard protocol that suggests use of the selected ion monitoring (SIM) method. Analysis was made of thirteen oil samples from the Pernambuco coast, in order to identify their degrees of similarity and the possible presence of oils from unreported spills. The use of eighteen diagnostic ratios and multivariate analysis revealed a cluster formed by eleven samples with biomarker distributions typical of oil from the 2019 spill. However, two samples had anomalous fingerprints, especially due to the absence of the 18α(H)-oleanane and 18β(H)-oleanane isomers. Both the CEN protocol applied for the classical biomarkers and a comprehensive Fourier transform mass spectrometry (FT-MS) analysis of polar compounds confirmed the dissimilarities between the samples. The findings suggested that these two oils could have originated from an event unrelated to the mysterious 2019 spill.

Development of Eurocode 3 and Research Contributions

This paper gives an overview on recent work regarding the revision of EN 1993 on European level including selected scientific and technical issues and a summary of the activities executed within the European Standardization committee CEN/TC250/SC3 “Design of Steel Structures“ under the chair of Prof. Dr.-Ing. Ulrike Kuhlmann. This includes the description of current normative developments for the 2nd Generation of Eurocodes which aim at an evolution by improvements and harmonisation of the existing codes. In addition, a technical review of selected rules is given on a number of issues, which support the code revision and reflect well the recent tendencies in steel structures.

Verification of the behaviour factors proposed in the second generation of Eurocode 8 for cross‐laminated timber buildings

AbstractAfter 20 years since the publication of the Eurocodes, in 2012, the European Commission gave mandate to the European Committee for Standardization (CEN) to develop a second generation of Eurocodes. Among the different parts of Eurocodes, a substantial revision process has been undertaken for the seismic design rules of timber buildings included in Eurocode 8 (EC8). In particular, a major effort has been made to implement the design rules for Cross‐Laminated Timber (CLT) buildings and to define the behaviour factors q for such structural type. The choice of the behaviour factor q for CLT buildings in the new “timber” chapter of EC8 has been made by examining several proposals available in literature. Most of these studies were not referred to any specific design provision and certainly could not have followed the design rules drafted in the second generation of Eurocodes. This paper presents a study aimed to verify whether the proposed values of the behaviour factors q are consistent with the attained seismic performances of CLT buildings designed in accordance with the new “timber chapter” of EC8. Parametric non‐linear static (pushover) analyses and a risk‐consistent approach, based on the use of Incremental Dynamic Analyses (IDA) and fragility curves were conducted to evaluate the performance of a few selected archetypes. The results obtained from the analyses and the risk‐consistent approach showed that the proposed values of q‐factor for CLT buildings in second generation of Eurocode, namely 2.30 and 3.20 for a ductility class 2 (DC2) and 3 (DC3) respectively, can be reasonably accepted.

Ambiguities in Regulations Aimed at Safety in Intentional Work with Biological Agents

The Czech Republic, like other member states of the European Union, has implemented Directive 2000/54/EC. However, the resulting form of the transposition does not fully correspond to the requirements set out in the directive. Above all, the omission of the terms containment and physical containment level, which are used not only in the directive, but also in the text of technical standards, is very problematic. As a result of the absence of the mentioned terms, it is very difficult for many employees to orient themselves in the Czech legal regulations focused on safety and health protection when working with biological agents. The article summarizes the requirements set by Czech regulations and compares them with the requirements of the Directive 2000/54/EC and technical standards. At the same time, it offers the reader a selection of the main regulations of a non-normative nature that have been created by international organizations (World health organization and European Committee for Standardization) in order to manage biological risk in the workplace.

Long-term monitoring of fish in a freshwater reservoir: Different ways of weighting complex spatial samples

Anthropogenic activities continue to pose the greatest challenges to freshwater ecosystems. Therefore, long-term monitoring is essential for the management and conservation of these resources. Monitoring programs for freshwater bodies often use a range of indicators, including biological elements such as fish. Existing European standard provides a depth-stratified gillnet sampling approach mainly in benthic habitats and at the deepest part of lakes to account for the uneven distribution of fish. However, the commonly used CEN (European Committee for Standardization) protocol does not weight sufficiently habitat volumes and underrepresent pelagic habitats to calculate whole-lake catch and biomass per unit effort (CPUE and BPUE, respectively). Extended European standard gillnet (4 larger mesh-sizes added in the geometric series) catch data collected over 18 years (2004–2021) in Římov Reservoir (Czech Republic) were used for a method comparison on indices for relative abundance and biomass of fish: CEN protocol without volume-weighting and two volume-weighted approaches. We also evaluated changes in species composition and trends in these fish population over time. Results indicated interannual changes in species composition, relative abundance, and biomass of fish community. The CEN protocol tended to put greater emphasis on benthic habitats which generally have larger CPUE and BPUE. Consequently, the two volume-weighting approaches produced lower estimates of the two parameters, with the exception of the most dominant pelagic bleak Alburnus alburnus (L.). All approaches consistently showed an increasing trend in whole-reservoir fish abundance and a decreasing trend in biomass over the study period. Following our assessment, we put forward the volume-weighting approach that considers the Volume of the depth Stratum (VOST) for weighting as the most realistic approximation of fish populations and therefore recommend its use.

State-of-the-art catalysts for clean fuel (methyl esters) production—a comprehensive review

There has been growing and recent interest in using non-edible feedstocks, such as waste animal fats, as an alternative to vegetable oils in biodiesel production to address the food versus fuel debate. Waste animal fats are cost effective and yield good quality biodiesel. Therefore, waste animal fats are appealing and excellent feedstocks to produce biodiesel. Commercially, the biodiesel is obtained by transesterification reaction of triglycerides present in oil/fat with alcohol in the presence of homogeneous base catalysts. However, free fatty acids found in low-quality oil feedstocks are particularly sensitive to homogeneous base catalysts, necessitating extra acid pretreatment and neutralization procedures that not only raise the overall expense of producing biodiesel but also create environmental contamination. Optimistically, the use of solid catalysts can offer an environmentally friendly, cost-effective and practical route for the manufacture of biodiesel from inexpensive oil feedstocks, including waste animal fat. The present review article covers catalyzed transesterification/esterification using various catalysts with particular focus on the use of heterogeneous catalysts when using waste animal fat as feedstock for biodiesel production. In particular, the properties of biodiesel obtained from waste animal fats are also compared to the biodiesel properties of standard organizations, such as the European Committee for Standardization (ISO) and the American Society for Testing and Materials (ASTM). Moreover, this paper also offers future research directions that can direct researchers to fill in knowledge gaps impeding the creation of efficient heterogeneous catalysts for long-term biodiesel generation. To the best of our knowledge, the valorization of waste animal fats from slaughterhouses is not feasible and has some techno-economic concerns. However, this technology is more desirable considering the environmental point of view to address the pollution problems caused by these wastes.