Methyl Ester Fuels Research Articles

Experimental investigation of the emission and performance of preheated and unheated garlic methyl ester fuels and diesel fuel in a diesel engine

It is thought that vehicles running on diesel fuel significantly impact climate change in the world. To reduce this negative effect, changing the fuel source without making any changes to the engines is a very attractive method. Considering the environment, climate change, living health, and the lifespan of fossil fuels, studies on biodiesel fuels, which can be an alternative to diesel fuel, are important. In the present study, garlic methyl ester (GME) was produced from crude garlic oil using the transesterification method. The impacts of preheated and unheated GME and its blends on a diesel engine with an air cooling system without any modification were researched. GME was used with diesel at 20% and 60% volumetric ratios and was also used at 100%. Experimental studies were conducted at five engine loads (1, 1.5, 2, 2.5, and 3 kW). The GME and its blends were tested at the specified loads, and the results were obtained. The GME and blends were then preheated at 70 °C, and the experimental studies were repeated under the same conditions. In the tests, NOx, CO, CO2, HC, smoke density, EGT, BSFC, in-cylinder pressure, engine torque, noise, vibration, and thermal image analyses were conducted. According to the results, CO 22.3%, HC 24.9%, smoke density 25.6%, torque 4.6%, cylinder pressure 5.2%, and EGT 11.5% decreased, whereas BSFC 11.2%, noise 1.4%, vibration 3.8%, CO2 6%, and NOx 18.2% emissions increased in GME and its blends compared to diesel. The highest measurement values were obtained with 100% GME fuel. It was observed that both increasing the GME ratio and the preheating process improved the emission and performance values. The results obtained show that GME and its blends can be easily used in diesel engines without any modification.

Numerical study on the effects of using different concentrations of FAME blends on the spray structure of the injection process

The present paper takes a closer look at the injection process characteristics for different conditions when there are used different FAME blends. Using a numerical approach, this work highlights the main implications and differences in terms of geometry, structure, and physical parameters of the injected fuel spray, when alternating the used fuels. In this attempt, AVL FIRE was used as simulation software solution giving the chance to alternate the used fuels and furthermore to create a direct link between the fuel properties, internal flowing, and jet spray characteristics. Because of the environmental and economic reasons, there are a growing tendency of using biofuel blends in increasing concentrations, as ample consumption of commercial fuels. As the physical properties of the Fatty Acid Methyl Ester fuels are very different compared with conventional diesel fuel, we expect that the fuel blends between them will show different behaviors in terms of internal nozzle flowing and thus it will generate different injection characteristics, being closely related with the biofuel concentration. The main objective of this paper is to set a dependency between the used fuels, nozzle geometry, and injection parameters that should be adapted, to meet the emissions standards and to obtain a properly burning.

Droplet evaporation modeling of electrified fatty acid methyl esters

The influence of electric charge on the evaporation characteristics of fatty acid methyl ester fuels from short to long carbon chain length is simulated using a validated evaporation model. A fuel droplet is assumed to undergo electrostatic fragmentation or fission in a manner which results in a large ‘residual’ droplet and a number of other smaller ‘sibling’ droplets, as has been experimentally observed in previous work. Droplet evaporation simulations are performed both for a non-reacting case and for a case where the sibling droplets burn at the adiabatic flame temperature. The simulations are complemented with measurements of biodiesel spray current taken from a charge injection atomizer, so as to enable use of experimentally measured charge as an initial condition in the simulation. Charge advantageously influences the evaporation time, particularly under the assumption that generated sibling droplets undergo combustion. The influence of charge, droplet Reynolds number and the physical properties of the methyl esters are examined, demonstrating similar overall behaviour among fuels, however showing that time histories are grouped by carbon chain length. The experimental data indicates that specific charge is a key driver behind reducing evaporation time as Reynolds number increases. However, the relationship between charge influence vs. Reynolds number diminishes in situations where sibling droplets burn. This contribution sheds light on the influence of electric charge on the vaporization of biodiesel fuels, and provides useful data which can guide future interpretation of charge influence on vaporization in reacting and non-reacting environments.

In Situ Enzymatic Conversion of Nannochloropsis oceanica IMET1 Biomass into Fatty Acid Methyl Esters.

Conventionally, production of methyl ester fuels from microalgae occurs through an energy-intensive two-step chemical extraction and transesterification process. To improve the energy efficiency, we performed in situ enzymatic conversion of whole algae biomass from an oleaginous heterokont microalga Nannochloropsis oceanica IMET1 with the immobilized lipase from Candida antarctica. The fatty acid methyl ester yield reached 107.7% for dry Nannochloropsis biomass at biomass to t-butanol to methanol weight ratio of 1:2:0.5 and a reaction time of 12 h at 25 °C, representing the first report of efficient whole algae biomass conversion into fatty acid methyl esters at room temperature. Different forms of algal biomass including wet Nannochloropsis biomass were tested. The maximum yield of wet biomass was 81.5%. Enzyme activity remained higher than 95% after 55 days of treatment (equal to 110 cycles of reaction) under the conditions optimized for dry algae biomass conversion. The low reaction temperature, high enzyme stability, and high yield from this study indicate in situ enzymatic conversion of dry algae biomass may potentially be used as an energy-efficient method for algal methyl ester fuel production while allowing co-product recovery.

Performance and pollutant emissions from transient operation of a common rail diesel engine fueled with different biodiesel fuels

Three fatty acid methyl ester fuels (from rapeseed, sunflower and soybean vegetable oils) and their blends (30% v/v) with diesel fuel were tested under New European Driving Cycle (NEDC) on an engine test bench. This allowed comparing engine pollutant emissions trends under transient operation. FAME fuels and their blends produced higher specifics emissions of nitrogen oxides (NOx), total hydrocarbons (THC) and carbon monoxide (CO) and lower smoke opacity in comparison with EN 590 reference fuel. The most important reason for obtaining these results was the impact of fuel properties on the electronic control unit (ECU) response, which was tuned for diesel fuel operation by the carmaker. This fact points out the potential of fatty acid methyl ester and its use, at high concentrations on road transport, for reducing greenhouse gases and pollutant emissions, by means of the optimization of electronic control unit settings when biodiesel fuel is used.

Experimental Investigation on Performance, Combustion and Emission Characteristics of a Low Heat Rejection Engine using Rapeseed Methyl Ester and Diethyl Ether

vBackground/objectives: Today, as a result of limited fuel resources and stringent emission standards, the methyl ester fuel has been focused on alternative fuels for I.C engine. Methyl ester fuels can be effectively used in low heat rejection engines (LHR), in which the surface temperature of the combustion temperature is increased by providing a thermal barrier coating. The main objective of our work is to reduce the engine exhaust emissions like HC and CO using diethyl ether in low heat rejection engine. Methods/Statistical Analysis: In this work, engine components like piston crown, cylinder head, and liner, inlet and exhaust valves of a diesel engine were coated with the ceramic material lanthanum zirconate by plasma spray technique. The effects of rapeseed methyl ester (biodiesel) produced by transesterification method and its blends with Diethyl ether (10% and 20% by volume) were studied in the low heat rejection engine. Findings: The thermal efficiency is found to be higher for diesel and biodiesel in the LHR engine. The results indicate that, B10 (10% Diethyl ether & 90% Biodiesel) and B20 (20% Diethyl ether & 80% Biodiesel) shows lower thermal efficiency compared with that straight biodiesel in low heat rejection engine. Applications/Improvements: Significant improvements were observed in engine exhaust emissions like CO and HC (except NOx) for all the diethyl ether blended biodiesel fuel in LHR engine. The higher oxygen content in the blended fuel reduces CO and HC emissions by 10% and 18% respectively compared to biodiesel in LHR engine.

Expanded Framework for the Prediction of Alternative Fuel Content and Alternative Fuel Blend Performance Properties Using Near-Infrared Spectroscopic Data

Partial least-squares (PLS) regression models can be constructed from near-infrared (NIR) spectroscopic data to identify and predict critical specification properties of jet and diesel fuels for quality surveillance prescreening. This same approach has also been used previously to identify Fischer–Tropsch synthetic fuels and fatty acid methyl ester fuels, predict their quantities in blends with jet and diesel petrochemical fuels, and even correct fuel property predictions when alternative fuel contents in blends would affect the predictions of the properties in question. The present work expands upon these previous results by incorporating several additional alternative fuel types into a more generalized alternative fuel content and property modeling framework than was developed previously. The framework consists of a single generalized PLS modeling solution to simultaneously accommodate multiple alternative fuels considered isoparaffinic in nature, as well as smaller-scale modeling solutions to accommodate individual alternative fuels that are not similarly isoparaffinic in nature. This expanded framework provides the means to allow NIR PLS models to predict and quantify alternative fuel contents in blends, and accurately predict affected fuel properties, in a robust fashion that, because of the use of more-generalized modeling than has been seen in previous work, better accommodates a future of unknown and unknowable alternative fuel types.

Soot formation in diffusion oxygen-enhanced biodiesel flames

The focus of this work is the experimental investigation of soot formation in coflow flames formed of two fatty acid methyl esters (FAMEs) by employing the light extinction/scattering technique. Three different sets of experiments were conducted in this study. In the first set, radial soot volume fraction (fv) profiles of flames of vaporized neat canola methyl ester (B100CME) and neat soy methyl ester (B100SME) fuels both using air as the oxidizer were obtained. In the second set of experiments, the effect of oxygen content in the oxidizer stream on soot formation was studied in both FAME formed flames by increasing the oxygen content in the oxidizer stream from 21% to 35%, 50% and 80%. In the third set of experiments, the effect of fuel blending on the formation of soot particulates was studied in flames formed using CME blended with No. 2 diesel. The blends consisted of 80% biodiesel/20% diesel (B80) and 50% biodiesel/50% diesel (B50). The flames were scanned in the radial direction at various heights above the burner (HAB). For the B100CME-air flame the measured soot volume fraction fv peak was 4.04 ppm and was located at the symmetry axis at a HAB of 16.25 mm. For B100SME-air, the fv peak was measured to be 4.22 ppm at approximately the same flame height as in the CME-air flame. For the B100CME oxygen enriched-air flames the peak values at 35%, 50% and 80% were 6.50, 5.82 and 3.22 ppm, respectively. It was observed that by increasing the oxygen content in the B100CME flame from 21% to 35% oxygen, the fv peak increases by approximately 61%. However, a further increase in oxygen content in the oxidizer stream suppressed soot formation. A similar trend in the fv was observed for B100SME oxygen-enhanced flames. Furthermore, the increase of diesel fuel in the blending of B50CME resulted in significantly higher fv values compared to the B80CME. The addition of oxygen content in the oxidizer stream in these blended fuel flames (from air to 35%) resulted in an increase in the fv peak of approximately 47% and 71%, respectively. Centerline temperatures were measured at various HAB for selected flames.

The high-temperature autoignition of biodiesels and biodiesel components

Ignition delay time measurements are reported for two reference fatty-acid methyl ester biodiesel fuels, derived from methanol-based transesterification of soybean oil and animal fats, and four primary constituents of all methyl ester biodiesels: methyl palmitate, methyl stearate, methyl oleate, and methyl linoleate. Experiments were carried out behind reflected shock waves for gaseous fuel/air mixtures at temperatures ranging from 900 to 1350K and at pressures around 10 and 20atm. Ignition delay times were determined by monitoring pressure and ultraviolet chemiluminescence from electronically-excited OH radicals. The results show similarity in ignition delay times for all methyl ester fuels considered, irrespective of the variations in organic structure, at the high-temperature conditions studied and also similarity in high-temperature ignition delay times for methyl esters and n-alkanes. Comparisons with recent kinetic model efforts are encouraging, showing deviations of at most a factor of two and in many cases significantly less.

Combustion and soot processes of diesel and rapeseed methyl ester in an optical diesel engine

In-cylinder combustion and soot processes for ultra-low sulphur diesel (ULSD) and rapeseed methyl ester (RME) fuels were investigated in an optically accessible high speed direct injection diesel engine (HSDI) using in situ optical and laser measurement techniques. High speed imaging techniques were used to study the spatial distribution of spray flames, soot formation and oxidation through simultaneous measurements of OH* chemiluminescence and natural soot luminosity, during the luminous combustion process. The amount of un-oxidised soot left in the cylinder after the end of luminous combustion for these fuels were investigated using planar laser induced incandescence (PLII). In addition to PLII, time resolved laser induced incandescence (TR-LII) technique was used simultaneously to explore crank angle resolved variation of primary soot particle size during the expansion stroke. The ignition for RME occurs earlier compared to ULSD, and the early phase of RME combustion proceeds quicker compared to ULSD. The flame lift off length (FLoL) and the length based on the first appearance of soot (SLoL) are longer for RME. The combined effect of relatively longer FLoL and the presence of fuel-bound oxygen reduced the overall soot formation process for RME. PLII data confirmed that the relative amount of soot left in the cylinder after the end of visible luminous combustion is less for RME, and the soot formed are oxidised well within the combustion chamber before it is exhausted out of the engine compared to ULSD. The measured in-cylinder primary soot particles are in the size range between 15 and 35nm and it decreases with crank angle. The sizes of particles generated from the combustion of RME were slightly smaller compared to ULSD.

Comparative Study of the Autoignition of Methyl Decenoates, Unsaturated Biodiesel Fuel Surrogates

The autoignition of methyl 9-decenoate and a mixture of methyl 5-decenoate and methyl 6-decenoate [methyl 5(6)-decenoate], biodiesel fuel surrogate compounds structurally representative of unsaturated compounds found in fatty acid methyl ester (FAME) fuels, has been studied using the shock tube technique. Measurements of ignition delay times were made in reflected shock-heated gases at pressures around 20 atm for fuel/air mixtures at equivalence ratios of 0.5, 1.0, and 1.5 and at a wide range of temperatures from 700 to 1300 K, spanning a range of temperatures relevant to autoignition in compression ignition engines. A comparison of ignition delay times for the methyl decenoates and methyl decanoate illustrates the influence of the presence and location of a double bond within the methyl ester carbon chain on low- and high-temperature reactivities. At high temperatures (>900 K), the three surrogate components have indistinguishable ignition delay. While in the negative temperature coefficient (NTC) and lo...

Characteristic of Particulate Matter (PM) of Diesel Engine Using Palm Oil Methyl Ester (PME) Fuel

Characteristic of Particulate Matter (PM) of Diesel Engine Using Palm Oil Methyl Ester (PME) Fuel

Gaseous emission comparison of a compression–ignition engine fueled with different biodiesels

In this study, it was performed a comparison of the performance and emissions of two methyl ester fuels: one obtained from animal fat and the other from crude canola oil, in a compression-ignition engine against diesel fuel. The experimental results compared with diesel fuel showed that significant reductions could be obtained by biodiesel derived from animal fat in carbon monoxide and oxides of nitrogen emissions. Carbon dioxide emissions showed a trend of decreasing with the biodiesel fuels. An increase in brake specific fuel consumption was observed for different biodiesel fuels when compared with diesel fuel. It was concluded that animal tallow methyl ester performed better than canola oil methyl ester, whereas slightly higher brake torque is observed with canola oil methyl ester.

Bioelement Status with Oral Administration of Fish Oil Methyl Ester and Diesel Fuel in Male Rats

This paper is a study on the effects on the amounts of trace elements in case of possible repeat accidental or environmental exposure with fish oil biodiesel. For this purpose, 35 male Wistar albino rats were used in the study. Rats were divided into five groups. The first group was determined as the control group. The rats in this group were gavaged orally with 250 mg/kg sunflower oil. The rats in the second and third groups were administered by oral gavage of 250 mg/kg (D1) and 500 mg/kg (D2) diesel fuel mixed with equal amounts of sunflower oil, respectively. The rats in the fourth group were administered by oral gavage of 250 mg/kg fish oil biodiesel (F1) and the rats in the fifth group were administered by oral gavage of 500 mg/kg fish oil biodiesel (F2), both mixed with equal amounts of sunflower oil. At the end of the study, bioelement concentrations in the serum and the kidney, lung, and liver tissues were measured using inductively coupled plasma-optical emission spectroscopy. It was observed that serum Ca, Mg, and Sr concentrations were significantly (p<0.001) higher and Cu concentration was significantly (p<0.01) higher in the control group than in the biodiesel groups. Kidney Mg concentration was significantly (p<0.01) lower in the control group than in the diesel groups. Kidney Mg concentration was significantly (p<0.001) lower in the D2 group than in the F2 group. Kidney Mg concentration was significantly (p<0.01) lower in the control group than in the diesel groups. Lung Cd, Co, Cu, Cr, Na, and Zn concentrations were different significantly higher in the control group than in the other groups. Liver Al concentration was different significantly higher in the control group than in the other groups. Liver Ca concentration was significantly (p<0.05) higher in the control group than in the biodiesel groups. Serum and lung tissue bioelements concentrations were lower in diesel and biodiesel groups than in control group. Due to consumption for biochemical reaction of these elements, bioelements concentration could be low in diesel and biodiesel groups. Some trace elements concentrations in the kidney and liver were very high in the diesel groups. High concentration of these elements in the diesel groups might cause toxic effects. Fish oil biodiesel could be chosen as an alternative fuel instead of diesel fuel.

Combustion Products of Petroleum Jet Fuel, a Fischer–Tropsch Synthetic Fuel, and a Biomass Fatty Acid Methyl Ester Fuel for a Gas Turbine Engine

We report combustion emissions data for several alternatives to petroleum based Jet A jet fuel, including a natural gas–derived Fischer–Tropsch (FT) synthetic fuel; a 50/50 blend of the FT synthetic fuel with Jet A-1; a 20/80 blend of a fatty acid methyl ester (FAME) with jet fuel; and a 40/60 blend of FAME with jet fuel. The chief distinguishing features of the alternative fuels are reduced (for blends) or negligible (for pure fuels) aromatic content and increased oxygen content (for FAME blends). A CFM International CFM56-7 gas turbine engine was the test engine, and we measured NOX, CO, speciated volatile organic compounds (including oxygenates, olefins, and aromatic compounds), and nonvolatile particle size distribution, number, and mass emissions. We developed several new methods that account for fuel energy content and used the new methods to evaluate potential fuel effects on emissions performance. Our results are categorized as follows: (1) regulated pollutant emissions, CO, and NOX; (2) volatile organic compound emissions speciation; and (3) particle emissions. Replacing all or part of the petroleum jet fuel with either FAME or FT fuel reduces NOX emissions and may reduce CO emissions. Combustion of FT fuel and fuel blends increases selectivities and in some cases yields of oxygenates and some hydrocarbon volatile organic compound emissions relative to petroleum jet fuel. Combustion of FAME fuel increases propene and butene emissions, but despite its oxygen content does not strongly affect oxygenate emissions. Replacing petroleum jet fuel with zero aromatic alternatives decreases the emissions of aromatic hydrocarbons. The fuel effects become more pronounced as the size of the aromatic molecule increases (e.g., toluene is reduced more strongly than benzene). Particle emissions are decreased in particle size, number density, and total mass when petroleum jet fuel is replaced with the zero aromatic fuels. The effects of fuel composition on particle emissions are most pronounced at lower power conditions, i.e., when combustion temperature and pressure are lower, and less efficient mixing may lead to locally higher fuel/air ratios than are present at higher power.

Production of hydrocarbons from fatty acids and animal fat in the presence of water and sodium carbonate: Reactor performance and fuel properties

The thermal degradation of free fatty acids and animal fat in a moving bed of sodium carbonate and 5wt% of water were carried out at 430±20°C at a pilot scale plant. During start-up the loading rates for a 60:40 mixture of oleic and stearic acids were 10kg/h resulting in a 69±5% of bio-crude. The acidity index was remarkably low within a range of 0.64–0.80mg KOH/g during 3weeks of operation. The loading rates for animal fat were increased from 10 to 40kg/h corresponding to a weight hourly space velocity of 0.03–0.1h−1 over a period of 6months. Heat transfer into the reactor was the limiting criterion. The main product with a yield of 65±5% was bio-crude showing an acidity index of 0.5–1.8mg KOH/g. The mean value for kinematic viscosity at 40°C was 1.78mm2/s. The net calorific value of bio-crude was 41.6MJ/kg. Coke deposits on sodium carbonate were determined to be 5±1%. The gaseous products ranged from 25wt% to 30wt%. The presence of CO2, H2, CH4, C2H6, C2H4 and C3 to C5 hydrocarbons as major components was established by gas chromatography. The gases were directly fed into an on-site gas line and used for heating purposes. The distillation curve of bio-crude from animal fat showed hydrocarbon based bio-fuels in the boiling ranges of gasoline and diesel. Upon rectification 66% of bio-diesel and 21% of bio-gasoline were obtained. This corresponds to a total yield of 43% bio-diesel and 14% bio-gasoline from animal fat. The bio-diesel had favorable low-temperature properties (cold filter plugging point=−18°C) with oxidation stability between that of mineral oil based diesel and fatty acid methyl ester fuels. The gasoline fraction lacked low-boiling hydrocarbons as indicated by a vapor pressure of 26kPa instead of 60-90kPa (DIN EN 228). Thus, water-cooled condensers need to be improved for a full-scale plant. The results are discussed in terms of German specifications for standard fuels.

Detailed chemical kinetic reaction mechanism for biodiesel components methyl stearate and methyl oleate

New chemical kinetic reaction mechanisms are developed for two of the five major components of biodiesel fuel, methyl stearate and methyl oleate. The mechanisms are produced using existing reaction classes and rules for reaction rates, with additional reaction classes to describe other reactions unique to methyl ester species. Mechanism capabilities were examined by computing fuel/air autoignition delay times and comparing the results with more conventional hydrocarbon fuels for which experimental results are available. Additional comparisons were carried out with measured results taken from jet-stirred reactor experiments for rapeseed oil methyl ester fuels. In both sets of computational tests, methyl oleate was found to be slightly less reactive than methyl stearate, and an explanation of this observation is made showing that the double bond in methyl oleate inhibits certain low temperature chain branching reaction pathways important in methyl stearate. The resulting detailed chemical kinetic reaction mechanism includes more approximately 3500 chemical species and more than 17,000 chemical reactions.

The effects of Al 2O 3–TiO 2 coating in a diesel engine on performance and emission of corn oil methyl ester

Today, as a result of increase in oil prices, limited fossil fuel resources, environmental consideration and global warming, the methyl ester fuels have been focused on alternative fuels. Methyl ester fuels can be used more efficiently in low heat rejection engines (LHR), in which the temperature of combustion chamber is increased by creating a thermal barrier. In this study, the piston, cylinder head, exhaust and inlet valves of a diesel engine were coated with the ceramic material Al 2O 3–TiO 2 by the plasma spray method. Thus, a thermal barrier was provided for the parts of the combustion chamber with these coatings. The effects of corn oil methyl ester that produced by the transesterification method, and No. D2 fuels’ performance and exhaust emissions’ rate were studied by using equal in every respect coated and uncoated engines. Tests were performed on the uncoated engine, and then repeated on the coated engine and the results were compared. A decrease in engine power and specific fuel consumption, as well as significant improvements in exhaust gas emissions (except NOx), were observed for all test fuels used in the coated engine compared with that of the uncoated engine.

植物系バイオ燃料によるディーゼル機関の性能ならびに排気特性に関する研究(熱工学,内燃機関,動力など)

Although some countries use esterificated fuel, which is made out of useless vegetable oil, it makes troubles which are emission of white and black smoke, becoming worse of engine start, and so on. Since biofuels are oxygenated fuels, there are concerns abous production of large amounts of aldehydes, which are oxygenated toxic substances. This paper examines the cause of precipitation of solids in fuel at low temperatures, looks at trends in production of aldehydes from biofuels, compares exhaust characteristics when using 3 types of biofuel and gas oil in a diesel engine, and clarifies what effect constituent fatty acids have on exhaust characteristics. As the percentage of saturated fatty acids increases, the cloud point and freezing point rise, and a certain degree of correlation is evident between the cloud point and freezing point. With methyl oleate, production of aldehydes begins to increase around 400, and the produced amount is small in the low temperature range. With methyl ester fuels, there is an increase in NO_x and a decrease in THC, CO and exhaust smoke density, compared to gas oil.

Characteristic fuel consumption and exhaust emissions in fully mechanized logging operations

A study was done using eight different logging machines (harvesters and forwarders) in clear-felling operations to quantify the associated fuel consumption, and to define the inherent relationship between engine output power and fuel consumption. Exhaust emissions were also calculated on the basis of mean fuel consumption values, obtained by measurements, and from the developed regression and correlation model for diesel and rapeseed methyl ester (RME) fuels. The calculation considered exhaust emissions associated with the manufacture, distribution, and combustion of the respective fuels. It was found that carbon dioxide emissions amounted to 9.63 kg/m3 of delivered timber for diesel fuel, and to 10.64 kg/m3 for RME. It was also found that when using RME only 2.82 kg/m3 of carbon dioxide emissions originated from fossil resources, therefore, it is only this amount that can be deemed an environmental load, confirming RME as a lesser environmental pollutant.