Biodiesel Combustion Research Articles

Fatty acid content and composition of sediments from Siberian eutrophic water bodies: Implications for biodiesel production

We studied lipids and fatty acids (FA) in bottom sediments from four Siberian water bodies, Bugach, Lesnoi and Krasnoyarsk freshwater reservoirs and brackish Shira lake, that differed in physico-chemical and biological conditions. We considered the potential of the bottom sediments as a feedstock for biodiesel production and estimated properties of the obtained biodiesel as a fuel on the basis of FA composition. Contents of lipids and FA in the sediments moderately varied and were generally close to the reported data from lacustrine and estuarine systems. We confirmed that long-term eutrophication of a water body resulted in the lipid-rich bottom sediments that make them a feedstock for biodiesel production. Each of the studied water bodies had specific FA composition of sediments likely due to different organic matter sources and transformation processes. Despite these differences in FA profiles, calculated key parameters (cetane number, iodine number and heat of combustion) of biodiesel produced from all the studied sediments met the limits established by current biodiesel standards. Thus, the variation in the sediment FA composition due to environmental characteristics of a water body likely has no principal significance for fuel properties of the obtained biodiesel.

Soot temperature and KL factor for biodiesel and diesel spray combustion in a constant volume combustion chamber

This paper presents measurements of the soot temperature and KL factor for biodiesel and diesel combustion in a constant volume chamber using a two-color technique. This technique uses a high-speed camera coupled with two narrowband filters (550nm and 650nm, 10nm FWHM). After calibration, statistical analysis shows that the uncertainty of the two-color temperature is less than 5%, while it is about 50% for the KL factor. This technique is then applied to the spray combustion of biodiesel and diesel fuels under an ambient oxygen concentration of 21% and ambient temperatures of 800, 1000 and 1200K. The heat release result shows higher energy utilization efficiency for biodiesel compared to diesel under all conditions; meanwhile, diesel shows a higher pressure increase due to its higher heating value. Biodiesel yields a lower temperature inside the flame area, a longer soot lift-off length, and a smaller soot area compared to diesel. Both the KL factor and the total soot with biodiesel are lower than with diesel throughout the entire combustion process, and this difference becomes larger as the ambient temperature decreases. Biodiesel shows approximately 50–100K lower temperatures than diesel at the quasi-steady stage for 1000 and 1200K ambient temperature, while diesel shows a lower temperature than biodiesel at 800K ambient. This result may raise the question of how important the flame temperature is in explaining the higher NOx emissions often observed during biodiesel combustion. Other factors may also play an important role in controlling NOx emissions. Both biodiesel and diesel temperature measurements show a monotonic dependence on the ambient temperature. However, the ambient temperature appears to have a more significant effect on the soot formation and oxidation in diesel combustion, while biodiesel combustion soot characteristics shows relative insensitivity to the ambient temperature.

Simulation of the evaporation of drops from palm and castor oil biodiesels based on physical properties

A reduction of oil reserves and an augmented production of greenhouse gases from fossil fuels have increased the use of biodiesel in internal combustion engines. Although physical and chemical properties of biodiesel and diesel are similar enough that allow the use of pure biodiesel in a traditional engine without considerable adjustments, differences in chemical structure of diesel and biodiesel change vaporization and combustion rates and can affect engine performance. In this study a model that can predict the evaporation rate of palm and castor oil biodiesel droplets at atmospheric pressure was developed. The model was validated with experimental data from the literature for the evaporation of n-heptane-droplets. The model estimates thermo-physical properties of biofuels using contribution group theory and was used to determine that castor oil biodiesel presents a lower evaporation rate than palm oil biodiesel due to differences in their physical properties (mainly density and vaporization enthalpy) which can be explained by a longer molecule and the presence of a hydroxyl groups in methyl ricinoleate, its main component.

Polycyclic Aromatic Hydrocarbons in Particulate Matter Emitted by the Combustion of Diesel and Biodiesel

Two sets of experiments were performed for collected particulate mass emitted directly from the exhaust of diesel engines burning diesel and biodiesel fuels: First, a diesel truck was used in the field, and in the second test, a similar diesel engine was used in the laboratory. The mass of particles and polycyclic aromatic hydrocarbons (PAH) was determined. No reduction was observed in the mass of particles per min using biodiesel relative to that produced when burning diesel. Pyrene and phenanthrene showed the highest mass concentrations in diesel and biodiesel in both tests. Reductions in these PAHs greater than 80% (in the truck field test) and 35% ± 11% (in the engine laboratory test) were observed when using biodiesel in any mixture thereof, with respect to diesel. The mean ± standard deviation of the ratios of BaA/(BaA + Chry) and (BbF + BkF)BghiP for diesel emissions were consistent with the literature. Four ratios amongst PAHs were proposed, with relative standard deviation < 10%, which suggests that these ratios could be used as emission markers for diesel and animal biodiesel blends (<B20).

Performance, combustion and emission characteristics of biodiesel derived from waste cooking oils

An experimental study was conducted on a Euro IV diesel engine to evaluate the performance, combustion and emission characteristics of pure biodiesel and its blend fuels. For each tested fuel, the performance and emissions were measured at four different engine speeds (800rpm, 1200rpm, 2400rpm and 3600rpm) under three different loads (25%, 50% and 100% load). The results showed that the use of biodiesel/blend fuels resulted in a higher brake specific fuel consumption, especially at low engine speed and partial load conditions. For example, at 25% engine load, the BSFC was found to be increased by 42% and 34.4% for biodiesel as compared to diesel at 800rpm and 1200rpm respectively. The brake thermal efficiency of biodiesel was found to be slightly higher compared to diesel at 50% and 100% load and the opposite tread was observed at 25% load. For combustion characteristics, a slightly shorter ignition delay and lower peak heat release rate were found for biodiesel compared to pure diesel. With respect to emissions, a slight reduction in the major emissions such as HC and NOx were observed with the use of biodiesel. But the opposite trend was seen at low engine speed, revealing that the low engine speed had a significant effect on the engine combustion and emission formation processes.

Influence of fatty acid unsaturation degree over exhaust and noise emissions through biodiesel combustion

Environmental concerns are driving the scientific community to search for alternative fuels to substitute fossil-based ones. In this context, biodiesel is the most extended alternative to fuel diesel engines due to its renewable nature. However, the chemical composition of the raw materials used to produce biodiesel is variable, thus providing a wide range of types of biodiesel showing diverse affinity to diesel engines. Moreover, depending on the fuel properties, engine exhaust and noise emissions may be affected. For these reasons, it is important to increase the knowledge about the implications of biodiesel chemical composition and properties over engine exhaust and noise emissions. An experimental study with vegetable oils (covering a wide range of fatty acids) to produce biodiesel has been carried out. Selected raw materials included high, medium and low saturated fatty acids, i.e. palm, sunflower, olive-pomace, coconut and linseed oil. Later, their methyl esters blended with diesel fuel were tested in a direct injection diesel engine. Effects of chemical properties of biodiesel on exhaust and noise emissions have been studied at several engine operating conditions. In general terms, results showed that the use of biodiesel/diesel fuel blends reduced the emissions of CO and noise, thus improving the sound quality, although, NOx increased. Particularly, it was found that the higher the unsaturation degree the higher the emission of NOx and the lower the CO emissions. A linear correlation between fatty acids unsaturation degree and sound pressure level was found at high engine power values. In sum, despite the increase on NOx, the use of unsaturated biodiesel as partial diesel fuel substitute is recommended to improve CO emissions, besides engine sound quality, therefore making the engine sound more pleasant.

On the spherically symmetrical combustion of methyl decanoate droplets and comparisons with detailed numerical modeling

This study presents an experimental effort and detailed numerical simulation of the burning process of an ester-based biodiesel fuel droplet – methyl decanoate (MD). The experiments are carried out using test droplets that are anchored to small SiC support structures (14μm diameter) and that burn in an ambience subjected to a low gravity level to promote spherical symmetry in the droplet burning process. The initial droplet diameters are 0.53–0.57mm and the combustion gas is normal atmospheric pressure air. A detailed numerical simulation of the burning process is also presented that features detailed MD combustion chemistry, radiative heat transfer, species diffusion, and phase change effects to predict the evolution of droplet and flame diameter. The analysis also incorporates a model for heat transfer through the droplet support structure.Predicted droplet and flame diameters are shown to agree within the range of uncertainty of the experimental data lending support to the transport model and combustion kinetics incorporated in the simulation. Effects of the tether fiber’s size, thermal conductivity, and Nusselt number on the droplet burning data are also examined. Results show that the fiber properties within the range investigated in this study do not significantly affect the burning process. Species and temperature distributions during the transient process of MD droplet combustion are detailed in this study. These comparisons and predictions for multi-phase combustion of MD that have not been seen in the literature provide validation for MD models associated with chemical kinetics and multi-physics and are therefore valuable for the study of ester-based biodiesel combustion.

STUDIES ON EFFECTS OF COMBUSTION CHAMBER GEOMETRY AND INJECTION PRESSURE ON BIODIESEL COMBUSTION

Combustion of biodiesels has inherent problems due to their high viscosity and low volatility. This paper relates the modification of engine combustion chamber design, for inducing turbulence to improve the combustibility of combustible mixture. A survey of literature shows that experimental studies have not been done on a tri-chambered piston for evaluating influence on the performance and emission characteristics using diesel blends as well. The objective of this work is to study the effect of combustion chamber geometry and injection pressure on performance and emissions of a biodiesel (Jatropha) fuelled multi-chambered piston diesel engine. The performance and emission characteristics were studied and it has been noticed that for the engine under consideration 200 bar injection pressure gives optimum performance.

Inadequacy of Optical Smoke Measurements for Characterization of Non–Light Absorbing Particulate Matter Emissions from Gas Turbine Engines

Analysis of particulate matter (PM) emissions from gas turbine engines, using the conventional smoke number (SN) technique, provides a measure of plume visibility. In this study, PM emissions were sampled from the exhaust of a small gas turbine engine, burning Jet A-1, and Biodiesel. SN results indicated that biodiesel significantly reduced visible emissions. Analysis of PM number and mass concentrations using a differential mobility spectrometer found that although nonvolatile PM was significantly reduced, biodiesel combustion produced a high fraction of volatile PM. Concurrent aerosol mass spectrometer measurements established that the condensable material was organic in composition. The condensation of volatile organics, not captured by the SN technique, significantly increased the total PM emissions. Application of the Society of Automotive Engineers Aerospace Recommended Practice 1179d for gas turbine engines is limited to visible plume characterization and thus is inadequate when combustion produces a large fraction of volatile or non–light absorbing PM emissions.

Fuel Qualities and Combustion Characteristics of Animal-Fats Biodiesel for Agricultural Hot Air Heaters

Purpose: Combustion and fuel qualities of the animal-fats biodiesel as a heating fuel for agricultural hot air heater were studied. Methods: Biodiesel (BD) was made from animal-fats by reacting with methanol and potassium hydroxide in the laboratory. The biodiesel made in the laboratory was tested for fuel and combustion qualities. Results: The kinematic viscosity and the calorific values of the biodiesels were measured. Kerosene based biodiesel, BD20 (K) showed 18 cSt at <TEX>$-20^{\circ}C$</TEX>. It seemed that BD100 was not suitable for a heating fuel under some temperature. As BD content increased, the calorific value decreased up to 40,000 J/g for BD100, while the calorific value of light oil was 45,567 J/g showing difference of 5,567 J/g, about 12% difference. Several different fuels including BD20 (biodiesel 20% + light oil 80%), BD50 (biodiesel 50% + light oil 50%), BD100 (biodiesel 100%), and light oil were tested for fuel combustion qualities for agricultural hot air heater, and their combustion performances were compared and analyzed. Flame dimensions of biodiesels and light oils were almost the same shape at the same combustion condition. Generally, the <TEX>$CO_2$</TEX> amounts of BDs were greater than light oil. However, in this study the differences were minor, so there was no significant difference existed between the BDs combustion and light oil. Conclusions: It seemed that quality was good for heating oil for agricultural hot air heater because of showing no barriers for continuous combustion and proper exhaust gas temperature and <TEX>$CO_2$</TEX> amount discharged. But, for fuel fluidity for higher BD content fuel could be a detrimental problem in situations where the outdoor temperature is lowered. As BD content increased, calorific value decreased up to 40,000 J/g for BD100. Calorific value difference between BD20 and light oil was about 1,360 J/g.

Combined effect of injection timing and combustion chamber geometry on the performance of a biodiesel fueled diesel engine

The rapid depletion of fossil fuels and environmental concerns make alternative fuels such as biodiesel more attractive. Biodiesel has properties comparable to ultra low sulfur diesel (ULSD), however certain properties of biodiesel such as viscosity, calorific value, density and volatility differ from ULSD. These properties strongly affect injection, air-fuel mixing and thereby combustion and performance characteristics of biodiesel in a diesel engine. In order to realize the full potential of biodiesel use in diesel engine certain modifications to engine design and injection system are required. This experimental study aims to optimize the combination of injection timing and combustion chamber geometry to achieve higher performance and lower emissions from biodiesel fueled diesel engine. Experiments were performed using a blend of 20% Pongamia Oil Methyl Ester (POME) by volume in ULSD (B20), in a single cylinder Direct Injection (DI) diesel engine equipped with pistons having Hemispherical and Toroidal Re-entrant Combustion Chamber (TRCC) geometries. The test results showed an improvement of 5.64% in brake thermal efficiency, a reduction of 4.6% in brake specific fuel consumption and a 11% increase of oxides of nitrogen (NOx) level for TRCC compared to baseline engine operated with ULSD due to better air-fuel mixing and retarded injection timing.

Development of a reduced biodiesel combustion kinetics mechanism for CFD modelling of a light-duty diesel engine

A reduced chemical kinetics mechanism has been developed and validated under zero-dimension and multi-dimensional engine simulations for a range of engine operating conditions and types of biodiesel fuel. The mechanism is first constructed by reducing a detailed MB/MB2D mechanism consisting of 301 species and 1516 reactions to 77 species and 212 reactions. The ignition delay periods and temporal evolutions of important species are in good agreement with those produced using detailed kinetics. The reduced mechanism is then combined with a skeletal modified n-heptane mechanism to account for actual biodiesel energy content and molecular structure when fuel blends are introduced. Two additional global reactions are also included to cater for the change in ratio between saturated and unsaturated methyl esters in the fuels. The combined mechanism (BOS-V2) consists of 113 species and 399 reactions with integrated nitrogen oxides (NOx) reaction kinetics. This mechanism is then further validated using OpenFOAM® for the computational fluid dynamics (CFD) engine simulations. Here, neat and B50 blends of coconut, palm and soy methyl esters are used. Good agreements in ignition delay, peak pressure, pressure trace, heat-release profile and emission trends are achieved between experimental and predicted data for all the tested fuels and engine operating conditions. The results show that the proposed mechanism gives reliable predictions of in-cylinder combustion and emission processes.

Evaluation and Treatment of Carbonyl Compounds and Fine Particles Emitted by Combustion of Biodiesels in a Generator

The main objectives of this study are the assessment of fine particles (PM2.5) and carbonyl compound emissions from an electrical generator fueled with biodiesels and the evaluation of the efficiency of a commercial 4-way catalytic converter toward these pollutants. Two different biodiesels were used: Soybean Oil fatty acid Methyl Esters (SOME) and Waste Cooking Oil fatty acid Ethyl Esters (WCOEE). Several biodiesel blends with petroleum diesel were tested (0%vol, 7%vol, 20%vol, and 50%vol). For all blends it was shown that particles are mainly composed of ultrafine particles with a diameter below 0.4 μm. The presence of a 4-way catalyst allows the reduction of the total number of particles emitted by at least 97%. However, the fraction of the smaller particles (PM0.1), which are particularly harmful to health, becomes predominant. The origin and concentration of biodiesel introduced in the fuel influence both the total number of emitted particles and their size distribution. The different behavior of the...

Sensitivity of Diesel Particulate Material Emissions and Composition to Blends of Petroleum Diesel and Biodiesel Fuel

A number of investigations have examined the impact of the use of biodiesel on the emissions of carbon dioxide and regulated emissions, but limited information exists on the chemical composition of particulate matter from diesel engines burning biodiesel blends. This study examines the composition of diesel particulate matter (DPM) emissions from a commercial agriculture tractor burning a range of biodiesel blends operating under a load that is controlled by a power take off (PTO) dynamometer. Ultra-low sulfur diesel (ULSD) fuel was blended with soybean and beef tallow based biodiesel to examine fuels containing 0% (B0), 25% (B25), 50% (B50), 75% (B75), and 100% (B100) biodiesel. Samples were then collected using a dilution source sampler to simulate atmospheric dilution. Diluted and aged exhaust was analyzed for particle mass and size distribution, PM2.5 particle mass, PM2.5 organic and elemental carbon, and speciated organic compounds. PM2.5 mass emissions rates for the B25, B50, and B75 soybean oil biodiesel mixtures had 20%–30% lower emissions than the petroleum diesel, but B100 emissions were about 40% higher than the petroleum diesel. The trends in mass emission rates with the increasing biodiesel content can be explained by a significant decrease in elemental carbon (EC) emissions across all blending ranges and increasing organic carbon (OC) emissions with pure biodiesel. Beef tallow biodiesel blends showed similar trends. Nevertheless, it is important to note that the study measurements are based on low dilution rates and the OC emissions changes may be affected by ambient temperature and different dilution conditions spanning micro-environments and atmospheric conditions. The results show that the use of biodiesel fuel for economic or climate change mitigation purposes can lead to reductions in PM emissions and a co-benefit of EC emission reductions. Detailed speciation of the OC emissions were also examined and are presented to understand the sensitivity of OC emissions with respect to biodiesel fuel blends. Copyright 2012 American Association for Aerosol Research

Detailed physical properties prediction of pure methyl esters for biodiesel combustion modeling

In order to accurately simulate the fuel spray, atomization, combustion and emission formation processes of a diesel engine fueled with biodiesel, adequate knowledge of biodiesel’s physical properties is desired. The objective of this work is to do a detailed physical properties prediction for the five major methyl esters of biodiesel for combustion modeling. The physical properties considered in this study are: normal boiling point, critical properties, vapor pressure, and latent heat of vaporization, liquid density, liquid viscosity, liquid thermal conductivity, gas diffusion coefficients and surface tension. For each physical property, the best prediction model has been identified, and very good agreements have been obtained between the predicted results and the published data where available. The calculated results can be used as key references for biodiesel combustion modeling.

Experimental investigations of comparative performance, emission and combustion characteristics of a cottonseed biodiesel-fueled four-stroke locomotive diesel engine

A large-bore, four-stroke, medium-speed, compression-ignition railway traction locomotive engine was fueled with cottonseed methyl ester (Biodiesel). The cottonseed methyl ester was stored for 6 months under ordinary storage conditions, and various fuel properties of this seasoned cottonseed methyl ester were evaluated. Various blends of cottonseed methyl ester (B10, B20, B50 and cottonseed methyl ester) were evaluated for engine performance, emissions and combustion characteristics of the locomotive engine compared to baseline diesel. Correlation of the fuel-injection performance parameters with the physical properties of biodiesel has been carried out. The engine was able to operate on cottonseed methyl ester without noticeable power loss. With cottonseed methyl ester, the thermal efficiency decreased marginally by 0.7% and the brake-specific energy consumption increased by 0.1 MJ/kWh at the rated power. Due to the lower calorific value of biodiesel, brake specific fuel consumption (BSFC) increased by 13.4% at eighth engine notch, nitrogen oxide emissions increased by 8% and particulate matter emissions decreased by 32% vis-a-vis mineral diesel. Nitrogen oxide emissions were found to be a function of injection timings, global oxygen/carbon ratios, time of the maximum mean in-cylinder temperatures and apparent heat release. Particulate matter emissions were found to depend on the air–fuel mixture’s oxygen/carbon ratio, fuel bound oxygen and fuel-injection pressure. The experiments were carried out to evaluate the in-cylinder pressure, heat-release rate, cumulative heat release, fuel-injection pressure, needle lift and fuel-injection velocities. Increased fuel-injection pressures (1000 bar compared to 900 bar for mineral diesel), advanced fuel-injection timings, shorter combustion duration, advanced in-cylinder pressures and higher heat-release rates were observed for biodiesel and blends. The findings of the present study have provided further insights into the combustion of biodiesel in locomotive engines.

Ab Initio Reaction Kinetics of Hydrogen Abstraction from Methyl Formate by Hydrogen, Methyl, Oxygen, Hydroxyl, and Hydroperoxy Radicals

Combustion of renewable biofuels, including energy-dense biodiesel, is expected to contribute significantly toward meeting future energy demands in the transportation sector. Elucidating detailed reaction mechanisms will be crucial to understanding biodiesel combustion, and hydrogen abstraction reactions are expected to dominate biodiesel combustion during ignition. In this work, we investigate hydrogen abstraction by the radicals H·, CH(3)·, O·, HO(2)·, and OH· from methyl formate, the simplest surrogate for complex biodiesels. We evaluate the H abstraction barrier heights and reaction enthalpies, using multireference correlated wave function methods including size-extensivity corrections and extrapolation to the complete basis set limit. The barrier heights predicted for abstraction by H·, CH(3)·, and O· are in excellent agreement with derived experimental values, with errors ≤1 kcal/mol. We also predict the reaction energetics for forming reactant complexes, transition states, and product complexes for reactions involving HO(2)· and OH·. High-pressure-limit rate constants are computed using transition state theory within the separable-hindered-rotor approximation for torsions and the harmonic oscillator approximation for other vibrational modes. The predicted rate constants differ significantly from those appearing in the latest combustion kinetics models of these reactions.

Simulation of biodiesel combustion in a light-duty diesel engine using integrated compact biodiesel–diesel reaction mechanism

This computational fluid dynamics (CFD) study is performed to investigate the combustion characteristics and emissions formation processes of biodiesel fuels in a light-duty diesel engine. A compact reaction mechanism with 80 species and 303 reactions is used to account for the effects of chemical kinetics. Here, the mechanism is capable of emulating biodiesel–diesel mixture of different blending levels and biodiesel produced from different feedstock. The integrated CFD-kinetic model was validated against a test matrix which covers the entire saturated–unsaturated methyl ester range typical of biodiesel fuels, as well as the biodiesel–diesel blending levels. The simulated cases were then validated for in-cylinder pressure profiles and peak pressure values/timings. Errors in the peak pressure values did not exceed 1%, while the variations in peak pressure timings were kept within 1.5 crank angle degree (CAD). For this reported work, in-cylinder formation mechanisms of nitrogen monoxide (NO) and soot from the combustion of biodiesel fuels such as coconut methyl ester (CME), palm methyl ester (PME) and soybean methyl ester (SME) were simulated and compared against that of the baseline diesel fuel. It is established here that an increase in the degree of unsaturation in biodiesel fuels can have detrimental effects on engine-out NO and soot concentrations. Biodiesel fuel with greater unsaturation level such as SME has the predisposition to produce greater thermal NO due to larger regions of high temperature achieved during combustion. Besides, the highly unsaturated SME has greater tendencies to produce acetylene which are precursors for prompt NO and soot, leading to higher engine-out emissions of these pollutants. In all, this study has demonstrated the feasibility of integrating a compact multi-component surrogate fuel mechanism with CFD to elucidate the in-cylinder combustion and emissions characteristics of biodiesel fuels. The knowledge acquired here is useful for the development of biodiesel usage strategies in light-duty diesel engines for mass adoption.

Development of a reduced biodiesel surrogate model for compression ignition engine modeling

Methylbutanoate (MB), a C4 methyl ester, represents the simplest surrogate that captures the chemical effects of the ester moiety in biodiesel and biodiesel surrogates. An updated chemical kinetic model has been developed to characterize the ignition and flame characteristics of MB. The mechanistic elements within this model that relate to the MB and smaller ester/oxygenate sub-mechanisms are drawn from the prototypical Fisher et al. model and from more recent theory and modeling efforts. The MB model development which is based on an iterative procedure involving global sensitivity analyses to identify elementary reactions that govern ignition and subsequent high level ab initio based theoretical updates to these reaction rates are presented. The MB model makes reasonable predictions of ignition delays and laminar flame speeds.The C5–C7 submechanisms from the LLNL n-heptane (NH) model were merged with the present MB model to obtain a detailed chemical kinetics model for a surrogate blend representing biodiesel. The detailed MB-NH model (661 species) was reduced using graph based techniques. The robust reduction techniques employed result in a reduced model (145 species) that is in good agreement with the detailed model over a wide range of conditions. 3-D compression ignition (CI) engine simulations utilizing this reduced chemistry model for MB-NH blends as a surrogate for biodiesel show good agreement with the experimental data suggesting the utility of this model for predictions of combustion and emission characteristics of biodiesel in realistic CI engine simulations.

Comparative in vitro cytotoxicity assessment of airborne particulate matter emitted from stationary engine fuelled with diesel and waste cooking oil-derived biodiesel

Biodiesel derived from waste cooking oil (WCO) is gaining increased attention as an alternative fuel due to lower particulate emissions and other beneficial factors such as low cost and utilization of waste oil. However, very little information is available on toxicity of airborne particulate matter (PM) emitted from biodiesel combustion. In this study, PM emitted from WCO-derived biodiesel (B100) was analyzed for its toxic potential together with ultra low sulphur diesel (ULSD) as a reference fuel and their blend (B50). Human lung epithelial carcinoma cells (A549) were used for this comparative toxicity study. Results indicate that cytotoxicity and oxidative stress were higher for B100 relative to ULSD. Furthermore, caspase 3/7 activity indicates that cell death induced by B100 was due to either caspase independent apoptotic process or other programmed cell death pathways. The toxicity was also evaluated for different engine load conditions. It was observed that at lower loads there was no significant difference in the toxicological response of B100 and ULSD. However, with increase in the engine load, B100 and B50 showed significantly higher toxicity and oxidative stress compared to ULSD.