Presence Of Biodiesel Research Articles

Hydrocarbon degradation strategy and pyoverdine production using the salt tolerant Antarctic bacterium Marinomonas sp. ef1.

One of the most concerning environmental problems is represented by petroleum and its derivatives causing contamination of aquatic and underground environments. In this work, the degradation treatment of diesel using Antarctic bacteria is proposed. Marinomonas sp. ef1 is a bacterial strain isolated from a consortium associated with the Antarctic marine ciliate Euplotes focardii. Its potential in the degradation of hydrocarbons commonly present in diesel oil were studied. The bacterial growth was evaluated in culturing conditions that resembled the marine environment with 1% (v/v) of either diesel or biodiesel added; in both cases, Marinomonas sp. ef1 was able to grow. The chemical oxygen demand measured after the incubation of bacteria with diesel decreased, demonstrating the ability of bacteria to use diesel hydrocarbons as a carbon source and degrade them. The metabolic potential of Marinomonas to degrade aromatic compounds was supported by the identification in the genome of sequences encoding various enzymes involved in benzene and naphthalene degradation. Moreover, in the presence of biodiesel, a fluorescent yellow pigment was produced; this was isolated, purified and characterized by UV-vis and fluorescence spectroscopy, leading to its identification as a pyoverdine. These results suggest that Marinomonas sp. ef1 can be used in hydrocarbon bioremediation and in the transformation of these pollutants in molecules of interest.

Simulation of wear map for biodiesel interacted automotive materials

Selection of material for automotive component has an important role to avoid wear problem that encountered in static and moving parts due to fuels used in the engine especially, biodiesel. Biodiesel compositions such as dissolved water, free water and emulsified water accelerate oxidation of metallic materials. During the combustion process, the biodiesel contributes to the corrosive wear of the engine components leading to the shortening of the life span. The early prediction of the wear behavior under severe conditions in presence of biodiesel would be a vital solution. Therefore, the main aim of this study is to propose a wear map simulation for examining wear phenomenon of automotive component materials in presence of biodiesel. Herewith, materials that come into contact with biofuel/biodiesel in automotive application are highlighted for better design and selection in the future. This study concluded that based on the wear map simulation proper selection of material with higher durability and wear resistant can offer a better future for economic and reliability of the components. The development of wear map with recommendation aids researchers making decisions and innovation on the metals engine components. Furthermore, a full explanation on the reaction between biodiesel and metals can increase the innovation in the automotive industry.

Ecotoxicity of soil contaminated with diesel fuel and biodiesel

Fuels and their components accumulate in soil, and many soil organisms are exposed to this pollution. Compared to intensive research on the effect of conventional fuel on soil, very few studies have been conducted on soil ecotoxicity of biofuels. Considering the limited information available, the present study evaluated the changes caused by the presence of biodiesel and diesel fuel in soil. The reaction of higher plants and soil organisms (microbial communities and invertebrates) was analysed. Conventional diesel oil and two types of biodiesel (commercial and laboratory-made) were introduced into the soil. Two levels of contamination were applied—5 and 15% (w/w per dry matter of soil). The plate method was used to enumerate microorganisms from soil contaminated with biodiesel and diesel fuel. Phytotoxicity tests were conducted by a 3-day bioassay based on the seed germination and root growth of higher plant species (Sorghum saccharatum and Sinapis alba). Fourteen-day ecotoxicity tests on earthworm were performed using Eisenia fetida. Based on the results of the conducted tests it was found out that the organisms reacted to the presence of fuels in a diverse manner. As to the microorganisms, both the growth and reduction of their number were noted. The reaction depended on the group of microorganisms, type of fuel and dose of contamination. The lipolytic and amylolytic microorganisms as well as Pseudomonas fluorescens bacteria were particularly sensitive to the presence of fuels, especially biodiesel. Fuels, even at a high dose, stimulated the growth of fungi. Monocotyledonous sugar sorghum plants were more sensitive to the presence of fuels than dicotyledonous white mustard. There was also a significant negative impact of contamination level on plant growth and development. Biodiesel, to a greater extent than conventional fuel, adversely affected the survival and volume of earthworms.

Experimental Investigation of Tribo-Corrosive Nature of Biodiesel and its Effect on Lubricating System

The population of the world is growing very rapidly, which results in the increasing demand of energy in the transportation sector and a precipitous diminution in the reserve of fossil fuel. The lack of alternatives for fossil fuel and the vulnerabilities of the environment encouraged many researchers to investigate biodiesel as the most promising fuel. Biodiesel diminishes the major environmental concerns and also it will fulfil the demand energy conservation and fuel. The present investigation has been carried out to study the effect of multiple parameters governing the tribo-corrosion behaviour of aluminium in the presence of biodiesel. Experiments were conducted with three types of oil, taking bio-oil as a composition to find out the effect of corrosion in the aluminium faces. A test rig was fabricated taking ASTM standard to perform morphological analysis of the sample, and a pin-on-disc test rig is used to execute standard wear testing of it. Localised melting was observed during the experiment for the last 30 s when a load was of 20 N at a speed of 4.2 m/s in the absence of any lubrication. But in the presence of lubrication, no such melting was observed due to lesser friction and whatever frictional heat generated was taken away by the contacting fluid. Further, the experimental study concludes that the corrosion rate was found much more in vapours as compared to the condition where samples are entirely immersed in biodiesel. Hence synergism of wear, friction, and corrosion related to this experimental study plays a vital role in the performance of biodiesel.

Pea cultivar Blauwschokker for the phytostimulation of biodiesel degradation in agricultural soil

Phytoremediation is a cost-effective and ecologically friendly process that involves the use of plants to uptake, accumulate, translocate, stabilize, or degrade pollutants. The present study was conducted to demonstrate the potential of pea (Pisum sativum L. spp. sativum) cultivar Blauwschokker to phytostimulate biodiesel degradation in an agricultural soil, considering the influence of biological remediation on selected physiological parameters of plants and the amount and activity of soil microflora. Biodiesel was spiked into soil in dose of 50 g kg−1 of dry mass soil. The results of the study showed that the rate of biodiesel degradation in the vegetated soil was higher than that occurring by natural attenuation. At the same time, biodiesel showed a positive effect on the growth, development, and activity of soil bacteria and fungi. Moreover, the obtained results showed an improvement in physiological parameters of plants, including an increase in chlorophyll a and total chlorophyll content and higher relative water content in leaves in the presence of biodiesel.

In situ acid catalysed transesterification of biodiesel production from Sterculia foetida oil and seed

ABSTRACTThe quantity of fossil fuel is declining year by year, and the pollutant also released to the environment which insist on the exploration of new alternative fuel. Biodiesel from non-edible seeds is of primary concern for increasing prices of crude oil and thereof preventing greenhouse gas emissions. In the present study, the production of biodiesel by In-situ acid catalyzed transesterification from Sterculia foetida oil and seeds were reported. GC-FID characterization of oil sample revealed the presence of long-chain fatty acids with a higher proportion of sterculic acid (32%). The operating parameters in acid transesterification process viz., the weight of the oil and biomass, solvent volume, acid volume, temperature and time were optimized using Placket-Burman design. The maximum biodiesel yield obtained for sterculia oil and seeds were 91.58% and 95.91% exhibiting volume of oil being the critical factor based on Plackett-Burman design. One-way ANOVA analysis showed that chosen parameters were statistically significant (P < .05) except for temperature. FT-IR analysis confirms the presence of biodiesel (1741 cm–1) obtained from the transesterification process.

Voltammetric determination of copper and tert-butylhydroquinone in biodiesel: A rapid quality control protocol

Trace amounts of copper decrease significantly the oxidative stability of biodiesel while antioxidants, mostly tert-butylhydroquinone (TBHQ), are commonly introduced to the biofuel to guarantee induction period values within regulatory limits. Hence, a simple method to monitor the most used antioxidant and the most deleterious contaminant in biodiesel can give a fast response on its quality. In this context, this work presents a simple, efficient, low cost and sensitive method for the simultaneous and direct determination of copper and the antioxidant TBHQ in biodiesel. The biodiesel samples were diluted in 90% (v/v) ethanol and 10% (v/v) water containing 0.1 mol L−1 HCl (final concentration) as the supporting electrolyte generating a homogeneous mixture in which Cu(II) and TBHQ were directly detected using the square wave voltammetry (SWV) on a gold working electrode. The presence of biodiesel in the selected electrolyte facilitated the separation of analyte peaks facilitating the treatment of data and quantification. The linear responses for the simultaneous determination were in the range between 5 and 100 μg L−1 and 4.2–81.5 mg L−1 for copper and TBHQ (R > 0.997), respectively. High precision (RSD = 4.0% and 3.9%, n = 20) and limit of detection (LOD) values of 0.31 μg L−1 and 1.0 mg L−1 (0.030 μg g−1 and 0.102 mg g−1 in biodiesel) for Cu(II) and TBHQ, respectively, were obtained. Recovery values between 97% and 104% for both copper and TBHQ were obtained.

Performance and Exhaust Gas Emission of Biodiesel Fuel with Palm Oil Based Additive in Direct Injection Compression Ignition Engine

Blending biodiesel in the diesel would increase the tendency of having a high viscosity fuel. For this reason, the addition of a small amount of additives into the blends may improve the engine performance and lead to better fuel consumption. The purpose of this paper is to experimentally investigate the performance and emissions generated by various mixtures of biodiesel and diesel with palm oil based additive in the compression ignition direct injection diesel engine of Yanmar TF90. Experiments were also conducted to identify the ideal biodiesel, diesel and the additive mixture that produces the optimum engine emission and performance. The experiment was conducted by using mixtures that consisted of 10%, 20% and 30% of biodiesel with and without the additives. From the results of the experiments, PB10 with 0.8 ml additives produced the highest braking power and lowest fuel consumption as compared to the diesel and the rest of the biodiesel blends. The presence of biodiesel and additives were found to not only improve the engine performance, but also led to the reduction of carbon emission. Although all the diesel, biodiesel and additive demonstrated low smoke emission with a complete combustion, a slight increase however, was observed in the NOx emission. In conclusion, PB10 is seen as the most ideal blend for diesel engine in terms of providing the most optimum engine emission and performance.

Some Studies on use of ternary blends of diesel, biodiesel and n-octanol

ABSTRACTDiesel is extensively used in India, however, also contribute to pollution. In this study, important physico-chemical properties of different ternary blends of diesel, waste cooking oil (WCO) biodiesel and n-octanol, are evaluated. Diesel and D80+WCB20+nO20 blend have almost similar density, calorific value, cetane index and CFPP. However, blends have higher kinematic viscosity and flash point as compared to diesel. GC-MS test shows the presence of 51.3% saturated and 44.24% unsaturated fatty acids. FTIR analysis shows a strong peak of carbonyl band at 1741 cm−1 which indicates the presence of biodiesel. Ternary blends are found to be a promising alternative to petroleum diesel.

Enhanced Degradation of Benzo[α]Pyrene in Coal Tar Contaminated Soils Using Biodiesel

The biodegradation of the potent carcinogen, benzo[a]pyrene (BaP), and other priority pollutants was investigated in un-weathered coal tar contaminated soil over a period of 150 days. Results from the laboratory microcosm experiments showed that after 60 days, the concentrations of BaP were significantly reduced by 81%, in the biodiesel amended samples compared to the 26% and 34% depletion in the control and nutrient-only amended microcosms, respectively. The 3-ring PAH anthracene was also almost completely biodegraded in the presence of biodiesel. However, phenanthrene degradation was significantly inhibited in these samples as only 3% reduction occurred as opposed to the 80% depletion observed in the control. A stepwise treatment approach conducted on the coal tar spiked soil also revealed a higher reduction in BaP (98%) in the biodiesel amended microcosms compared to the control (29%) and further enhanced the depletion of phenanthrene by 51% after 60 days of adding biodiesel to soil initially treated with nutrients. Toxicity assays showed that biodiesel amended microcosms stimulated phosphatase enzyme activity and exhibited a lower toxic response to Microtox Vibrio fischeri. Overall, the pattern observed in the removal of the PAHs using biodiesel, suggests the co-metabolic action of ligninolytic fungi, probably via lignin peroxidases, as also evidenced from the visible growth of moulds after 14 days of amendment. The enhanced removal of carcinogenic PAH and the reduced toxicity observed in soil after biodiesel amendment, indicates that this bioremediation technique has potential for full scale field trials.

Critical aggregates concentration of fatty esters present in biodiesel determined by turbidity and fluorescence.

Biodiesel for combustible engine is available as mixture of fossil diesel and fatty esters obtained by transesterification of vegetable oils. The use of biodiesel reduces the amount of SOx, mainly. However, it was already observed that biodiesel has a different behavior in environment in cases of accidental spill and groundwater contamination. It was noticed that the biodegradation of hydrocarbons (cyclic and aliphatic) in the presence of biodiesel are speeded, although the mechanism is still unclear. Considering the chemical structure of fatty esters, it was investigated the formation of aggregates in water solution by fatty esters present in commercial biodiesel. In Brazil, biodiesel is composed by 95% of fossil diesel and 5% of fatty esters mixture. In this work, fatty esters were treated as neutral surfactant, i.e., it was treated as a molecule with polar and non-polar part. Turbidity and fluorescence were used to determine the critical aggregates concentration (CAC). Water solutions containing fatty esters were examined exploiting changes in turbidity and fluorescence intensity of pyrene. Abrupt changes were attributed to aggregates formation, following the same behavior of traditional amphiphilic compounds. It was determined the CAC for ethyl palmitate, ethyl stearate, ethyl oleate, and ethyl linoleate. The values of CAC for fatty esters varied from 1.91 to 4.27μmol/L, while CAC for the mixture of esters (biodiesel) was 2.01 for methyl esters and 1.19 for ethyl esters, both prepared using soybean oil. The aggregates formation was also determined by fluorescence measurements considering the changes in intensity of peaks I and III of pyrene. Pyrene senses the changes in environment polarity. The values found of CAC by fluorescence for individual ethyl esters varied from 1.85 to 3.21μmol/L, while mixtures of ethyl esters was 2.23 and 2.07μmol/L for mixture of methyl esters. The results clearly showed that fatty esters form aggregates and might be responsible for speed degradation of compounds by accommodation of them in inner part of aggregates.

Using biodiesel as a green solvent in the polymerization reactions: the attempt to separate the biodiesel from the polymer by thermal treatment

In this work, the products of the polymerization reaction of epoxidized methyl esters with phthalic anhydride catalyzed by 2-methyl-imidazole, in the presence of biodiesel as a green solvent, were evaluated. The presence of biodiesel enabled reaction at 180 °C during 40 min in a system with good thermal conductivity, homogeneous conditions, and products with physical aspect varying from rubber to high viscous liquid. The products include polyesters, with and without biodiesel, were characterized by: DSC—Differential Scanning Calorimetry, TGA—thermogravimetric analysis, and TGA/MS -TGA coupled to Mass Spectrometer, swelling tests, plane strain compression, and morphological analysis using scanning electronic microscopy (SEM). Considering that biodiesel presents a temperature degradation around 215 °C and the polyesters around 320 °C, a simple thermal treatment was introduced to separate the solvent biodiesel from the reaction products. This treatment includes heating until 250 °C and consequent cooling to the room temperature. The second heating, up to 500 °C, was used to prove, through TGA/MS, that the thermal treatment (heating until 250 °C) not affected the polyester matrix and is sufficient to remove biodiesel.

Lubricated sliding wear of SAE 1045 and SAE 52100 steel against alumina in the presence of biodiesel, diesel and a 50:50 blend of those fuels

The purpose of this work was to evaluate the sliding wear characteristics of SAE 1045 and SAE 52100 steels with different microstructures in the presence of pure biodiesel, a biodiesel-diesel blend (50% diesel+50% biodiesel) and commercial diesel fuel. Non-lubricated tests (dry) were also performed for comparison. For SAE 1045, samples were given a hardening heat treatment (austenitization at 830°C and water quenching). For SAE 52100, the heat treatment was austenitization at 850°C followed by oil quenching. Tempering at 100°C and 300°C was used for SAE 1045, and tempering at 100°C and 200°C was used for SAE 52100. As a result, the samples had four different hardness and microstructure combinations: tempered martensite in SAE 1045 and tempered martensite with chromium carbides in SAE 52100. Wear testing was performed using a pin-on-disk tribometer, 1.8m/s sliding speed, 14.7N load and 4400m sliding distance following the ASTM G99-04 standard. Wear track surfaces were characterized using microindentation hardness and scanning electron microscopy. The results exhibited a tendency to decrease wear width, volume loss and wear coefficient when adding biodiesel to diesel for both SAE 1045 and SAE 52100 steels. Martensite produced by heat treatments increased the wear resistance. For both SAE 1045 and SAE 52100 steels, abrasive wear is dominant in both dry and lubricated conditions.

Enhanced bioremediation of crude oil in polluted beach sand by the combination of bioaugmentation and biodiesel

Biodiesel produced from rapeseed oil was used as a cost-effective and sustainable agent to enhance crude oil biodegradation in sand microcosms. The initial concentration of crude oil and total petroleum hydrocarbon (TPH) was 20,000 and 18,750 mg/kg, respectively. The mass ratio of biodiesel to crude oil was 0 (designated T1), 1:10 (designated T2), 1:4 (designated T3), and 1:2 (designated T4). After 80 days of incubation, the total removals of TPH and PAHs were 68.6 and 61.5% in T1, 78.0 and 67.3% in T2, 86.3 and 76.2% in T3, 72.2 and 57.9% in T4, respectively. Higher amounts of biodiesel reduced TPH biodegradation due to the decreased transfer of substrates caused by dilution effect. The addition of biodiesel stimulated bacterial growth during the initial period but the petroleum hydrocarbon degradation is not always correlated with the density of bacteria in the presence of biodiesel. Dehydrogenase activity (DHA) and polyphenol oxidase (PPO) activity increased greatly after the beginning of incubation. From then on, DHA continuously decreased with time. T3 had the highest DHA and PPO activity from day 30 to the end of the experiment. The lowest toxicity was observed in T3 at day 80, and T3 showed the highest degradation rate constant.

Effects of Biodiesel Contamination on Oxidation and Storage Stability of Neat and Blended Hydroprocessed Renewable Diesel

The present work investigates the effects of biodiesel contamination on conventional and renewable marine diesels, i.e., NATO F-76 and HRD-76. The physical properties and chemical composition of F-76, HRD-76, and biodiesel were measured, including viscosity, density, peroxide value, heat of combustion, and acid number. Long-term (ASTM D4625) and accelerated (ASTM D5304) test methods were used to investigate the influence of biodiesel contamination on storage stability of HRD-76, F-76, and their blends. The impact of biodiesel contamination on oxidation stability of neat and blended fuels was also studied by conducting test ASTM D2274. In addition, the influence of biodiesel contamination on physicochemical properties after stressing the fuel was investigated according to the ASTM methods. The presence of biodiesel at contaminant levels did not have significant effects on the fuel properties or storage and oxidation stability of neat and blended HRD-76 or F-76. Properties of contaminated samples were deter...

Influência do biodiesel de soja na biodegradação anaeróbia do benzeno e tolueno

A influência do biodiesel de soja na biodegradação dos hidrocarbonetos monoaromáticos benzeno e tolueno foi estudada sob condições anaeróbias em dois microcosmos montados com água subterrânea sintética, inóculo metanogênico, benzeno, tolueno e biodiesel. Na presença de biodiesel não foi observada biodegradação do benzeno e do tolueno. Com a biodegradação do biodiesel ocorreu a formação de acetato e metano, uso do sulfato e um aumento de 45 vezes no número de bactérias sulfato-redutoras. Esses resultados mostraram que, na mistura com benzeno e tolueno, o biodiesel foi biodegradado tanto sob condições de sulfato-redução quanto metanogênicas e que sua presença estimulou o crescimento da biomassa.

Influence of diesel and biodiesel fuel-contaminated soil on microorganisms, growth and development of plants

The paper presents the results of studies concerning the phytotoxicity of biodiesel and its diesel oil blends with a germination and root elongation test. The paper also analyses the effect of fuel on the number and activity of soil microorganisms and the reaction of plants used in the research. Fuel was introduced into the soil at a concentration of 10 and 50 g/kg dry mass soil. Based on the test results, it was found that from among 19 plants species representing 5 families taxonomically, only 4 species showed resistance to the presence of the fuel in soil, regardless of their type and dose (Glycine max (L.) Merill, Helianthus annuus L., Lupinus luteus L., cv. Lord and Pisum sativum L., cv. Eureka). Fuel generally reduced the number of heterotrophic microorganisms, and stimulated the growth of decomposing microorganisms and content of biomass. Significant differences in the number and activity of microorganisms were associated with the presence of biodiesel in the soil. The fuel had a negative influence on the biometric and physiological parameters of plants. A shorter length of shoots and roots was noted, especially in objects with biodiesel, reduced water content, and general content of assimilation pigments.

A preliminary study for the photolysis behavior of biodiesel and its blends with petroleum oil in simulated freshwater

With the increasing use of biodiesel and its blends with petroleum fuel, the corresponding environmental issues also occur during its production, application and transportation. The photolysis behavior for biodiesel and the impacts of biodiesel on the photo-oxidation of petroleum hydrocarbons in simulated freshwater was studied by irradiated with ultra violet (UV) and simulated sunlight in the present study. The results indicated that the photolysis rates of fatty acid methyl esters (FAMEs) were mainly depended on their degree of saturation, slightly on water matrices and the initial concentration of biodiesel, regardless of biodiesel sources. Similar results were observed for total organic carbon (TOC) removal rates; however, TOC removal rates were slightly dependent on the initial concentration of biodiesel. The presence of humic acid and pyrogallic acid or lake water matrices slightly inhibited the removal rates of TOC. The photolysis rates of individual petroleum hydrocarbons with and without the presence of biodiesel followed similar rules. In brief, alkanes with light molecular weights were transformed faster than those with heavy molecules, the removal of polycyclic aromatic hydrocarbons (PAHs) were more significantly than alkanes, and the removal of alkylated PAHs (APAHs) increased concurrently with the alkylation level in each family. The presence of biodiesel only inhibited the photolysis of some heavy alkanes and PAHs, not for all other petroleum hydrocarbons. Biodiesel, as a surfactant-like material, could stabilize small oil droplets initially formed by agitation, therefore, these droplets experience longer lifetimes in the water phase before re-aggregating into larger globules and rising to the surface. The apparent solubility of petroleum hydrocarbons, especially for those with heavier molecular weights, has been enhanced in the presence of FAMEs. In this scenario, light needs to penetrate water phase to degrade these targets compared with diesel alone. The direct contacting opportunities between UV light and targets, and radicals produced to attack targets were reduced, which finally resulted in the inhibited photolysis rates of some heavy molecular weight hydrocarbons.

Biodiesel in Brazil: A Market Analysis and Its Economic Effects

The commercial production of biodiesel in Brazil began in 2005 and increased in such a way that the country has become one of the largest producers in terms of volume in 2012. This study aims to analyze the biodiesel market in Brazil and its socio-economic effects resulting from the mandatory addition of biodiesel in the distribution system of mineral diesel. This work is characterized as a qualitative and exploratory study. The technical procedures adopted include literature research and data collection from government agencies involved. It is highlighted that the Programa Nacional de Producao e Uso de Biodiesel no Brasil - PNPB (“National Program for Production and Use of Biodiesel in Brazil”) was designed for the purposes of: promoting rural development; the growth of biodiesel production plants; and positively impact the environment. The survey showed the following results: i) significant increase in investment in renewable energy, especially biodiesel, ii) a high unused capacity in the biodiesel production plants; iii) a high dependence on soy for biodiesel production, iv) unfavorable prices of oilseeds; v) high concentration of the biodiesel market; vi) difficulty in standardizing the biodiesel auctions; vii) a small increase in inflation; viii) increased generation of income, employment and Gross Domestic Product (GDP) due to the presence of biodiesel in the energy market. It was found that by adding a percentage of biodiesel to diesel oil caused positive impacts on the national economy, contributing to improvement in employment policies, income distribution, environmental issues, technological and regional development.

Bioremediation strategies for diesel and biodiesel in oxisol from southern Brazil

Leaks and spillages during the extraction, transport and storage of petroleum and its derivatives may result in environmental contamination. Biodiesel is an alternative energy source that can contribute to a reduction in environmental pollution. The aim of the present work was to evaluate biodegradation of diesel, biodiesel, and a 20% biodiesel-diesel mixture in oxisols from southern Brazil, using two bioremediation strategies: natural attenuation and bioaugmentation/biostimulation. Fuel biodegradation was monitored over 60 days by dehydrogenase activity, CO2 evolution and gas chromatography. The bacterial inoculum employed for bioaugmentation/biostimulation consisted of Bacillus megaterium, Bacillus pumilus, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia and PCR-DGGE using 16S RNAr primers showed that some members of this consortium survived in the soil after 60 days. The biodegradation of pure biodiesel was higher for bioaugmentation/biostimulation than for natural attenuation, suggesting that the addition of the microbial consortium, together with adjustment of the macronutrient ratio, increased biodiesel degradation. The results of dehydrogenase and respiratory activity, together with GC analysis, suggested that the presence of biodiesel may, by stimulating general microbial degradative metabolism, increase the biodegradation of petroleum diesel. The microbial community was altered by both treatments, with natural attenuation producing a lower diversity index than the amended soil. The bioaugmentation/biostimulation strategy was showed to have a high potential for cleaning up soils contaminated with diesel and biodiesel blends.