Genotoxicity of syrian hamster lung cells treated in vivo with diesel exhaust particulates

Polycyclic aromatic hydrocarbons extracted and concentrated from diesel exhaust particulates have been shown to be mutagenic and carcinogenic, but attempts to induce pulmonary tumors through chronic inhalation of diesel exhaust by experimental animals have failed. We have attempted to resolve this incongruity by measuring chromosomal damage in lung tissue of chronically exposed hamsters, using the highly sensitive test for genotoxic chemical agents, sister chromatid exchange (SCE) analysis. To determine the degree of responsiveness of the test system to both diesel exhaust particulates and benzo(a)pyrene (BaP), these agents were instilled intratracheally into anesthetized hamsters as suspensions in 0.25 ml volumes of Hank's balanced salt solution (HBSS). Lung tissues from these animals were subsequently cultured in vitro and chromosomes from the resulting cell divisions were scored for exchanges of chromatin between sister chromatids. Control animals, treated weekly with 0.25 ml of BSS for 10 weeks, showed an average value of 12 SCE's per cell, while animals treated weekly with 200 ng BaP over a 10-week period showed an average of 17 SCE's per cell. HBSS, given as a single treatment, also produced an average of 12 SCE's per cell in control animals, but animals treated with a single instillation of 12.5 μg BaP showed an average SCE value of 19. These data confirmed that the procarcinogen BaP can be metabolically activated by lung cells in vivo and also demonstrated the efficacy of using this technical approach to study the effect of chemical mutagens that enter the lungs. Diesel exhaust particulates, administered in a range from 0 to 20 mg per hamster over a 24 h exposure period, produced a linear SCE dose-response ranging from 12 to 26 SCE's per metaphase. This curve suggested that a concentration of 3 mg of diesel particulates per hamster would not produce a statistically significant increase in SCE's above control values. One group of 8 hamsters, chronically exposed to diesel exhaust particulates for 3 months showed an average of 12 SCE's per cell. This was equivalent to a set of 5 control animals which also showed an average of 12 SCE's per cell. Although the scope of this study was limited, the data demonstrated that diesel exhaust particulates can induce genotoxic damage but a 3-month exposure to 6 mg/m³ of diesel exhaust particulates was insufficient to produce measurable mutagenic changes in lung cells. This negative response is consistent with the results from other studies in which similar exposures failed to produce pulmonary tumors.     

Mutagenic and carcinogenic potency of extracts of diesel and related environmental emissions: Summary and discussion of the results

The proposed conversion from gasoline powered automobiles to diesel powered vehicels has prompted the Environmental Protection Agency to evaluate the potential health effects associated with exposure to diesel emissions. At present, there is no direct epidemiological link between this exposure and human health. Therefore, a research program was constructed to compare the health effects associated with diesel emissions with those from other emission sources for which epidemiological information was available. The emission sources chosen were cigarette smoke, roofing tar, and coke oven. An additional comparative emission source which was a gasoline catalyst engine. Respirable particles from a variety of combustion sources have the potential of being carcinogenic and mutagenic. The objective of these studies was to determine the relative biological activity of the organic material adsorbed on these particles in both in vitro mutagenesis and in vitro and in vivo bioassays. The organic extracts from the following series of emission sources were quantitatively bioassayed in a matrix of tests for their carcinogenic and mutagenic activity: (1) a light-duty Oldsmobile diesel 350 engine; (2) a heavy-duty Caterpillar diesel engine; (3) a light-duty Nissan engine; (4) a Volkswagen Rabbit diesel engine; (5) cigarette smoke; (6) roofing tar; (7) coke oven; and (8) a gasoline catalyst Mustang. The test matrix consisted of the following bioassay: reverse mutation in Salmonella typhimurium; mitotic recombination in Saccharomyces cerevisiae; DNA damage in Syrian hamster embryo cells (SHE); sister chromatid exchange in CHO cells; gene mutation in L5178Y mouse lymphoma cells, Balb/c 3T3 mouse embryo fibroblasts and CHO cells; viral enhancement of SHE cells; oncogenic transformation in Balb/c 3T3 cells; and skin tumor initiation in SENCAR and C57 black mice. The results of this test matrix are discussed.     

Mutagenic and carcinogenic potency of diesel and related environmental emissions: Salmonella bioassay

Due to the expected increase in the percentage of diesel vehicles in the United States, the Environmental Protection Agency must evaluate the health effects associated with exposure to diesel emissions. Respirable particles from a variety of combustion sources have the potential of being carcinogenic and mutagenic. The objective of these studies was to determine the relative biological activity of the organic material adsorbed on these particles in in vitro mutagenesis bioassays. The organic extracts from the following series of emission sources were bioassayed in the Salmonella assay for mutagenic activity: (1) a light-duty Oldsmobile diesel 350 engine; (2) a heavy-duty Caterpillar diesel engine; (3) a light-duty Nissan engine; (4) a Volkswagen Rabbit diesel engine; (5) cigarette smoke; (6) roofing tar; (7) coke oven; and (8) a gasoline catalyst Mustang. This paper provides a comparison of these sources within the Salmonella bioassay and also demonstrates how bacterial systems can be used as a quality assurance measure in in vivo testing.     

DNA-binding studies with diesel exhaust particle extract

This study examines whether chemical components from diesel exhaust particulates react with DNA to form covalently bound adducts. Experiments in this report describe the in vitro reaction of purified DNA with a dichloromethane extract of diesel exhaust particulates in the absence or presence of enzyme activation by rat liver microsomes. The reactivity of the particle extract was compared to that of benzo[a]pyrene metabolites using low temperature fluorescence techniques which detect small quantities of polycyclic aromatic compounds bound to DNA. Incubation of DNA with the particle extract in the presence of microsomal enzymes produced no detectable fluorescent adducts in contrast to model experiments using benzo[a]pyrene. However, addition of the particle extract to incubation mixtures containing benzo[a]pyrene markedly decreased formation of benzo[a]pyrene-DNA adducts because the particle extract inhibits microsomal enzymes which activate benzo[a]pyrene and other polycyclic aromatic hydrocarbons. In the absence of microsomal enzymes, fluorescent material was detected in DNA exposed to high concentrations of the particle extract, but probably not as a result of covalent binding because the mutagenic activity of the particle extract remained unchanged during prolonged incubation with DNA. This stability is in contrast to the rapid decrease in mutagenic activity of benzo[a]pyrene-4,5-oxide during incubation with DNA. Thus, direct mutation of bacteria by the particle extract may require activation by bacterial enzymes as is known to occur with nitroaromatic compounds.     

Mutagenic and carcinogenic potency of extracts of diesel and related environmental emissions: In vitro mutagenesis and oncogenic transformation

Extracts from emissions of four diesel engines, a gasoline engine and three related environmental samples were tested in four in vitro assay systems designed to detect carcinogenic or mutagenic activity of chemicals. Samples from three of four diesel extracts, the gasoline engine, and all three related samples were positive in an enhancement of viral transformation assay. Two diesel samples, the gasoline engine extract and extract from coke oven emissions were positive for mutation induction in Chinese hamster ovary cells. Only the gasoline engine extract and the coke oven sample were positive in a DNA fragmentation assay using alkaline sucrose gradients. Experiments using chemical transformation of Syrian hamster embryo cells as an assay method have not been completed.     

Effects of EGR,swirl augmentation techniques on combustion of biodiesel/ethanol and their blends in a diesel engine

The diminishing resources and continuously increasing cost of petroleum in association with their alarming pollution levels from diesel engines have caused an interest in finding alternative fuels to diesel which are renewable and sustainable. Emission control and engine efficiency are two most important parameters in current engine design. The impending introduction of emission standards such as Euro IV and Euro V is forcing the research towards developing new technologies for combating engine emissions. The classification of Euro IV and V norms is applicable to heavy-duty engines in Europe, where as Euro 5 is applicable to light-duty engines. This paper presents the effects of exhaust gas recirculation (EGR), swirl augmentation techniques and ethanol addition on the combustion of Honge oil methyl ester (HOME) and its blends with ethanol in a diesel engine. From the experimental work conducted, it is found that the combustion of HOME plus up to 15% ethanol blend in a diesel engine operated with optimised parameters of injection timing 23° Before Top Dead Centre and compression ratio 17.5 results in acceptable combustion emissions and improved brake thermal efficiency (BTE). The addition of ethanol increased BTE with reduced hydrocarbons (HCs), CO and smoke emissions. However, NO _x emissions increased dramatically. Use of appropriate EGR reduces NO _x to acceptable levels. The implementation of swirl augmentation techniques further resulted in increased BTE and considerable reduction in tail pipe emissions such as smoke, HCs, CO and NO _x . The effect of swirl by providing grooves on the piston was taken into consideration to find the overall biodiesel engine performance, which gives scope for further studies.     

Mutagenic and carcinogenic potency of extracts of diesel and related environmental emissions: In vitro mutagenesis and DNA damage

The Saccharomyces cerevisiae D3 recombinogenic assay, the assay for forward mutagenesis in L5178Y mouse lymphoma cells, and the sister chromatid exchange (SCE) assay using Chinese hamster ovary cells were used to evaluate the in vitro mutagenic and DNA-damaging effects of eight samples of diesel engine emissions and related environmental emissions. The recombinogenic assay was not sufficiently sensitive for this evaluation, but mutagenicity was detected in the L5178Y mutagenesis assay following exposures of the cells to all of the emission samples, and DNA damage in the SCE assay was induced by most of the emission samples in the presence and absence of metabolic activation. The observation of positive results in the absence of activation indicated that the samples contained substances that were direct-acting mutagens and DNA-damaging agents.     

Effects of compression ratio,swirl augmentation techniques and ethanol addition on the combustion of CNG–biodiesel in a dual-fuel engine

The diminishing resources and continuously increasing cost of petroleum in association with their alarming pollution levels from diesel engines has led to an interest in finding alternative fuels to diesel. Emission control and engine efficiency are two of the most important parameters in current engine design. The impending introduction of emission standards such as Euro IV and Euro V has forced research towards developing new technologies for combating engine emissions. This paper examines the effects of compression ratio, swirl augmentation techniques and ethanol addition on the combustion of compressed natural gas (CNG) blended with Honge oil methyl esters (HOME) in a dual fuel engine. The present results show that the combustion of HOME and 15% ethanol blend with CNG induction in a dual-fuel engine operated in optimized parameters at an injection timing of 27° Before Top Dead Centre and a compression ratio of 17.5 resulted in acceptable combustion emissions and improved brake thermal efficiencies. The implementation of swirl augmentation techniques increased brake thermal efficiencies (BTEs) and considerably reduced combustion emissions such as smoke, HC, CO and NO_x. The addition of ethanol also increased BTEs. However, at more than 15% of ethanol in HOME, NO_x emissions increased dramatically.     

Experimental investigation of diesel engine using EGR and fuelled with Karanja oil methyl ester

Karanja oil methyl ester (KOME), a biodiesel prepared from Karanja oil, a potential source of non-edible oil in India and a prospective alternative to the diesel fuel, shows comparable performance and considerable reduction in emissions except NO_x. Exhaust gas recirculation (EGR) is a popular method of reducing the NO_x emission. The aim of this experimental work was to study the potential of the cooled EGR in a direct injection compression ignition engine operating with the KOME and its blend. The study was conducted with the different EGR rates. Performance and emission parameters were compared by using diesel, KOME and its blend employing EGR and with the same fuels without EGR. The study also differentiates the effect of EGR on KOME and its blend with the neat diesel. The effect of EGR was found to be slightly higher for KOME biodiesel and its blend than for neat diesel. Increased NO_x emission using KOME biodiesel was also found to be reduced by using EGR.     

Enhanced susceptibility to infection in mice after exposure to dilute exhaust from light duty diesel engines

A series of experiments was conducted in which groups of mice were first exposed for various durations to diluted exhaust from light duty diesel engines and then briefly to an infectious aerosol generated by nebulizing cultures of a bacterial pathogen (Streptococcus). Typically, postinfection mortality was significantly greater in groups exposed to exhaust than in their corresponding control groups exposed to purified air only. Data of recent diesel and of past diesel- and catalyst-treated gasoline engine exhaust experiments suggest a somewhat greater excess mortality from (enhanced susceptibility to) bacterial infection in mice exposed to diesel exhaust than in those exposed to catalytic gasoline exhaust. Limited data on acute tests of NO₂ and acrolein vapor alone suggest that the infectivity-enhancing effect of diesel exhaust could be accounted for in large part by these components. Exposures to diesel exhaust, NO₂, or acrolein did not enhance the mortality response to a viral pathogen (A/PR8-34).     

A study of diesel emissions on Drosophila

A sex-linked recessive lethal test was performed on male fruit flies of the species Drosophila melanogaster, (Oregon-R strain), exposed to an approximate five-fold dilution of exhaust from a diesel engine. The eight hour exposure was achieved by drawing diluted diesel exhaust from a three cubic meter stainless steel exposure chamber housing laboratory animals through a two liter reaction flask modified for use with Drosophila. A preconditioned sampling bag was used to collect the emissions after passing through the exposure chamber containing the flies. Results of analyses performed on the diesel exhaust mixture showed the following: carbon dioxide—0.17%, carbon monoxide—12.2 ppm, hydrocarbons—11.6 ppm, nitrogen oxide—3.8 ppm, nitrogen dioxide—2.9 ppm, sulphur dioxide—1.0 ppm, and particulates—2.18 mg/m³. Two broods of the F₂ generation were investigated for the occurrence of recessive lethal events. These broods approximated the developing gametogenic stages of mature sperm (P₁ matings on days 2 and 3 postexposure) and spermatocytes (P₁ matings on days 8 and 9). Additionally, the F₃ generation was evaluated for the occurrence of mosaic recessive lethal events which might escape detection in the F₂ generation. An equal number of F₂ and F₃ flies for both broods served as concurrent controls. Results indicate that, under the conditions tested, the diesel exhaust did not increase the mutation frequency of the exposed flies (F₂ rate = 0.30%, F₃ rate = 0%) when compared to the concurrent controls (F₂ rate = 0.37%, F₃ rate = 0.15%).     

Pulmonary function changes in Chinese hamsters exposed six months to diesel exhaust

Chinese hamsters were exposed for eight hours per day to automotive diesel exhaust emissions which were diluted with air (18 to 1) and had a particulate level of 6.4 mg/m³. Pulmonary function measurements were made after six months exposure. Body weight (BW), lung weight (LW), vital capacity (VC), residual volume by water displacement (RV_w) and by gas dilution (RV_D), alveolar volume (V_A), and carbon monoxide transfer factor (D_LCO) were measured. LW showed a significant increase in the diesel exposed animals (P < 0.01) while VC, RV_W, and D_LCO showed decreases (P < 0.01). Static deflation volume-pressure curves showed depressed deflation volumes for diesel exposed animals when volumes were corrected for body weight and even greater depressed volumes when volumes were corrected for lung weight. However, when volumes were expressed as percent vital capacity, the diesel exposed animals had higher lung volumes at 0 and 5 cm H₂O. Results of the pathological examination of the lung tissue will be necessary for final analysis of our findings. However, preliminary interpretation indicates possible emphysematous changes which are compatible with the observed decrease in D_LCO.     

Studies on the use of low-volatile non-edible oils in a thermal barrier-coated diesel engine

Owing to the ever-increasing vehicle population, the consumption of diesel fuel in the transportation, agricultural and industrial sectors has increased at an alarming rate. This has led to rapid fossil fuel depletion, ozone depletion and environmental degradation, which have become a serious concern. Search for alternative renewable and clean energy fuel sources to mitigate the emissions of greenhouse gases is continuing, and attempts to find different techniques for efficient utilization of these fuels are also undertaken. Biodiesel being an oxygenated fuel obtained from vegetable oils has received greater attention over the years as a promising alternative to diesel fuel. However, vegetable oils exhibit high viscosity, poor volatility and poor cold-flow characteristics. These characteristics can cause the following problems in the engine when run for a longer duration: injector coking, severe engine deposits, filter gumming, piston ring sticking and thickening of lubrication. These problems can be eliminated or minimized by adopting suitable fuel processing techniques to obtain biodiesels from vegetable oils. The fuel processing techniques vary widely, which include transesterification, supercritical methanolysis, ultrasonic and continuous microwave-assisted transesterification methods. In the present study, the transesterification method is effectively used to obtain biodiesels from non-edible oils of honne and cotton seed. The biodiesels obtained from these oils were used in the unmodified diesel engine to check their feasibility as diesel engine alternatives. Different thermal barrier coatings (TBCs) were applied on the piston, cylinder head, and inlet and exhaust valve surfaces of the diesel engine in order to make it a fully adiabatic engine. The engine with such TBCs is called a low heat rejection engine. For the present study, the TBC of partially stabilized zirconia (PSZ) and aluminium oxide (Al₂O₃) were selected. Finally, the performance of the diesel engine fuelled with different biodiesels in both conventional and thermal barrier-coated modes was compared. The thermal barrier-coated engine with the PSZ version showed better performance with increased nitric oxide emissions when compared with the Al₂O₃ coating.     

Metaphase analysis, micronuclei assay, and urinary mutagenicity assay of mice exposed to diesel emissions

Female Swiss mice were exposed 8 h/day to diesel exhaust for 1, 3, and 7 weeks. Urine was collected overnight for 4 days prior to sacrifice while the mice continued to be exposed for eight hours during the day. The presence of mutagens was determined by the Ames Salmonella test. One hour prior to sacrifice each mouse received 1 mg/kg colcemide. After sacrifice, the marrow from each femur was obtained. The marrow from one femur was used to prepare slides for metaphase analysis and the other for micronuclei assay. Other mice received IP 50 mg/kg cyclophosphamide 24 h prior to sacrifice or 1 μmole/kg benzo(a)pyrene in each of four daily doses prior to sacrifice and served as positive controls. The Ames Salmonella assay of the unconcentrated urine after 1, 3, and 7 weeks and concentrated urine after 7 weeks exposure to diesel exhaust did not significantly vary from clean air controls. In the micronucleus test, and metaphase analysis, cyclophosphamide produced a strong positive response and the 7 week diesel exposure was not different from clean air controls.     

Salmonella/microsome mutagenicity assays of exhaust from diesel and gasoline powered motor vehicles

Motor vehicle exhaust from prechamber injection diesel and gasoline powered passenger cars, sampled during US FTP 1973 test cycles and comprising both particulate matter and compounds condensable at ambient temperature, has been assayed for mutagenicity in the Salmonella/microsome test. Mutagenic components were to a large extent active in the absence of the mammalian microsomal preparation. The mutagenicity of both particulate matter and condensate from diesel exhaust and condensate from gasoline exhaust was decreased in the presence of the microsomal preparation whereas the mutagenicity of particulate matter from gasoline exhaust was enhanced by microsomal activation. A comparison between the investigated diesel and gasoline exhaust samples shows that the mutagenic effect in the Salmonella test of the diesel exhaust is more than ten times higher than that of the gasoline exhaust. Fractionation with respect to polarity indicates that the mutagenic components mainly are distributed in neutral aliphatic, aromatic, and oxygenated fractions. Tests for mutagenic monofunctional nitroarenes by an anaerobic assay indicate that such compounds at most are marginally present in the exhaust samples as compared with their presence in airborne particulate matter collected in an urban environment.     

Production of renewable and sustainable fuel from Calliandra calothyrsus and its utilisation in compression ignition engines

Alternative fuels have several advantages compared to fossil fuels as they are renewable, biodegradable, provide energy security, foreign exchange saving as well as help in addressing environmental concerns and socio-economic issues. Therefore, renewable fuels can be used predominantly as a fuel for transportation and for applications in power generation. Shaft power application is a key factor for economic growth and prosperity and depends crucially on the long-term availability of energy from sources that are affordable, accessible and environmentally friendly. In this context, the main objective of the present study was to implement the production of bioethanol from Calliandra calothyrsus, a potential lignocellulosic raw material for the cellulose-to-bioethanol conversion process that can be used as an alternative resource to starch- or sugar-containing feedstock. This study addresses a new pretreatment method known as hydrothermal explosion using C. calothyrsus for ethanol production. The present study also involves experimental investigations on a single-cylinder, four-stroke, direct-injection diesel engine operated with Honge oil methyl ester (biodiesel) and ethanol and its comparison with a neat diesel fuel mode of operation. The results revealed that optimal parameters for bioethanol production from C. calothyrsus were 2% acid concentration (HCl), 100°C temperature and 80 min retention time. For a diesel engine operated with a HOME–bioethanol blend, the experimental results showed a 3–4% decrease in brake thermal efficiency with a 8–10% increase in hydrocarbon and carbon monoxide emission levels and a 15–18% decrease in nitric oxide emission levels when compared with a neat diesel fuel mode of operation.     

In vivo detection of mutagenic effects of diesel exhaust by short-term mammalian bioassays

Male Chinese hamsters were exposed to diesel exhaust and clean air for six months at the Center Hill Facility of the U.S. Environmental Protection Agency in Cincinnati, Ohio. The animals were kept in specially constructed inhalation chambers and exposed to clean air or diesel exhaust for eight hours daily. The animals were sacrificed and slides prepared to study the mutagenic effects of diesel exhaust by four in vivo short term mammalian bioassays. Sperm morphology bioassay revealed a 2.67-fold increase in sperm abnormalities in the animals exposed to diesel exhaust as compared to those exposed to fresh air. Micronucleus bioassay revealed a 50% increase in the number of micronuclei in polychromatic erythrocytes obtained from animals exposed to diesel exhuast. However, no increase in sister chromatid exchange or chromosomal abnormalities was observed in bone marrow cells of animals treated with diesel exhaust. During these studies a decrease in mitotic index was observed in animals treated with diesel exhaust.     

Effect of hydrogen addition to CNG in a biodiesel-operated dual-fuel engine

Alternative fuels for diesel engine applications are gaining more prominence as they have numerous advantages compared to fossil fuels. They are renewable, biodegradable; provide food and energy security and foreign exchange savings. They address environmental concerns and socio-economic issues as well. Gaseous fuels such as compressed natural gas and hydrogenated compressed natural gas (HCNG) appear more attractive fuels for diesel engine applications operated in dual-fuel mode. Such dual fuel engines can replace considerable amount of liquid-injected pilot fuels by gaseous fuels besides being friendly to the environment. A small quantity of liquid fuel injected towards the end of the compression stroke initiates combustion of the inducted gas in the dual-fuel engines. The main advantage of dual-fuel engines is their lower nitrogen oxides (NO_x) and particulate emissions. Hence renewable fuels such as biodiesels and gaseous fuels can be used predominantly for transportation and power generation applications. Gaseous fuels are clean burning and are more economical as well. A suitable carburettor was designed to supply a stoichiometric mixture of air and HCNG to the modified diesel engine operated in dual-fuel mode. The biodiesel used in this study is derived from Honge oil called the Honge oil methyl ester (HOME). This paper presents the performance, combustion and exhaust emission characteristics of a single cylinder, four stroke, direct injection, stationary diesel engine operated on HOME and HCNG in dual-fuel mode. From the results it is observed that HOME–HCNG combination gave lower brake thermal efficiency (BTE) and improved emission levels when compared with diesel/HOME in single fuel operation. Lower smoke and particulate matter were obtained with dual-fuel operation. Comparative measures of BTE, peak pressure, pressure–crank angle variation, smoke opacity, hydrocarbon, carbon monoxide and NO_x emissions have been made and analysed.     

Introduction to and experimental conditions during the first year of the GMR chronic inhalation studies of diesel exhaust

A chronic exposure study was initiated to determine the effects of diesel exhaust on the health of experimental animals. For this purpose, test atmospheres of clean air (control) or freshly diluted diesel exhaust at concentrations of 250, 750, and 1500 μg/m³ were supplied to four 12.6 m³ inhalation chambers which housed rats and guinea pigs. Diesel aerosol size and concentration, as well as chamber temperature and relative humidity, were continually monitored and controlled to maintain the exposure dose levels and an environment of 22±2°C and 50%±20% relative humidity. The concentrations of CO and NO_x were found to be 5.8±1.0 mg/m³ and 7.9±1.0 mg/m³ above ambient in the chamber containing 1500 μg/m³ of particulate. Animals were supplied from the chambers, on a random basis, for both intramural and extramural studies throughout the exposure period. The experiment ran uninterrupted for over twelve months with mean diesel particle mass concentrations within 2% of the target values.     

Combustion and emission characteristics of a direct injection CI engine when operated on Marotti oil methyl ester and blends of Marotti oil methyl ester and diesel

This paper presents a feasibility study of Marotti oil biodiesel as an alternative to diesel fuel for a compression ignition engine. Marotti oil is inedible and available mainly in the state of Kerala. The oil is extracted from Marotti seeds. However, the high viscosity, poor volatility and cold flow characteristics of many vegetable oils in general, and Marotti oil in particular, can cause problems such as injector coking, severe engine deposits, filter gumming, piston ring sticking and thickening of lubrication from long-term use in diesel engines. These problems can be eliminated or minimised by transesterification of the vegetable oils to form monoesters. Although transesterification improves the fuel properties of vegetable oil, the viscosity and volatility of biodiesel are still worse than for petroleum diesel fuel. Subsequently, Marotti oil was converted into its methyl ester by the process of transesterification. The methyl ester was blended with diesel in various proportions to obtain different blends of Marotti oil with diesel. The performance, emission and combustion characteristics of Marotti methyl ester and its blends with diesel were studied and the results were compared with the base line data generated for diesel operation. Experiments were conducted using an injection timing of 23° before top dead centre (BTDC) and an injection pressure of 205 bar at various power outputs and at a constant rated speed of 1500 rpm. The engine manufacturer specifies an injection timing of 23° BTDC and injection pressure of 205 bar for the standard diesel fuel operation. The heat release rates, maximum rate of pressure rise, ignition delay and combustion duration for these fuel combinations were obtained.

From the results obtained, it was observed that the biodiesel produced from Marotti oil and its blends with diesel have slightly reduced brake thermal efficiency and increased smoke, hydrocarbon, carbon monoxide and reduced NO _x emissions compared with diesel-only operation. The investigation showed that the B20 biodiesel blend of Marotti oil with diesel produced better performance in terms of higher brake thermal efficiency, lower specific fuel consumption and comparatively lower emissions compared to the other blend ratios considered.