biodegradability of biodiesel fuel of animal and vegetable origin

Egle Sendzikienea

Violeta Makarevicienea

Prutenis Janulisa

Dovile Makareviciuteb

a Laboratory of Chemical andBiochemical Research forEnvironmental Technology,Institute of Environment,Lithuanian University ofAgriculture,Kaunas, Lithuania

b JSC “Biocentras”,Vilnius, Lithuania

Biodegradability of biodiesel fuel of animal andvegetable origin

One of the positive features of biofuel concerning environmental protection is its highbiodegradability. Fuel is considered to be biodegradable if not less than 90% of itdegrades within 21 days. The aim of this work was to determine the biodegradability ofvarious kinds of fatty acid methyl esters and their mixtures with fossil diesel fuel innatural environments. It was determined that fatty acid methyl esters meet therequirements for biodegradability set by the EU. Of rapeseed oil fatty acid methylesters (RME), 91.2% degraded within 21 days, compared to 94.2% of rapeseed oilfatty acid ethyl esters, 98.3% of linseed oil fatty acid methyl esters (LSME), 90% oftallow fatty acid methyl esters, and 92.5% of pork lard fatty acid methyl esters (LME),while the amount of degraded fossil diesel fuel reached only 57.3%. The biodegrad-ability of multi-component biofuels containing RME, LSME and LME is similar; the bestis of a mixture of 70% RME, 6% LSME and 24% LME. It was determined that morethan 90% of multi-component biofuel and fossil diesel fuel mixtures degrade within21 days when they contain 35% and more of multi-component biofuel.

Keywords: Biodegradability, fatty acid methyl esters, mixtures, fossil diesel fuel.

Eur. J. Lipid Sci. Technol. 109 (2007) 493–497 DOI 10.1002/ejlt.200600243 493

1 Introduction

The rising costs of fossil energy resources, the decreaseof natural resources and the increase of environmentalpollution related to the usage of fossil fuel lead us tosearch for the best ways of using the local renewableresources of energy. The use of locally produced biofuelwould create conditions to preserve the balance of eco-systems, decrease environmental pollution, strengthenenergetic independence, and improve resident occupa-tions and the balance of national trade.

Concerning environmental protection, the positive featureof biofuel is its high biodegradability in natural conditions.Fuel is considered to be biodegradable if not less than 90%of it degrades within 21 days. There are several methodsapplied to the researches in biodegradability [1–3].

Biodegradability in an aquatic environment can be deter-mined by considering the emission of carbon dioxide (CO2)[2] and by using the method of gas chromatography [4].

When the method of the analysis of CO2 emission is used,the theoretical amount of CO2 is calculated and theamount of CO2 that is emitted under aerobic conditions

by microorganisms if there is enough feeding medium ismeasured. The emitted amount of CO2 is proportional tothe biodegradability of the substratum. When rapeseedoil fatty acid methyl esters (RME) were examined, it wasnoticed that in 28 days 77–89% of CO2 was emitted, whilein the case of fossil diesel fuel it was just 18% [5]. Whenmixtures of rapeseed oil fatty acid ethyl esters (REE) andfossil diesel fuel (D) (REE-D) were analysed, it was deter-mined that the more REE the mixture contains, the biggeris the emission of CO2. When the mixture contains 63%REE and 37% fossil diesel fuel, 60% of CO2 is emittedwithin 28 days [4–6].

In gas chromatography analysis, the method of inner andouter standard is used, the analysed fuel is extractedand the decrease in the amount of fuel is determined.When the method of gas chromatography is used, theresults received are higher than in the case of the analy-sis of CO2 emission: 100% in 2 days, compared with84% in 28 days of REE and 48% of fossil diesel fuelagainst 18% [5]. Zhang and co-workers used the meth-od of gas chromatography to determine that 88% ofRME degraded in 28 days, while the amount of fossildiesel fuel degraded during the same period was just26% [4].

Several other scientists confirmed these results [6–9].Stolz compared the microbiological degradability of soy-bean oil fatty acid methyl esters (SME) and the biode-gradability of fossil diesel fuel in fresh water and soil underaerobic and anaerobic conditions [10]. Fossil diesel fuel

Correspondence: Violeta Makareviciene, Laboratory of Chemi-cal and Biochemical Research for Environmental Technology,Institute of Environment, Lithuanian University of Agriculture, Stu-dentu 11, LT-53361 Akademija, Kaunas r., Lithuania. Phone/Fax:1370 7-52292, e-mail: [email protected]

© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.ejlst.com

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494 E. Sendzikiene et al. Eur. J. Lipid Sci. Technol. 109 (2007) 493–497

degrades four times more slowly than SME under aerobicconditions. SME biodegrades even under anaerobicconditions.

The biodegradability of fuel in Europe is determined bythe CEC L-33-T-82 method. The prepared samples areanalysed by the method of infrared spectroscopy, and themaximum absorption of the C–M stretch of CH2-CH3

band is fixed when the wavelength is equal to 2930 cm–1.This method helped to determine that 99.6% of biodieselfuel degrades within 21 day [11], while a mixture contain-ing 20% of biodiesel fuel degrades twice as quickly asfossil diesel fuel [12].

According to the analysis of scientific researchers, therewas no data found concerning the biodegradability of ani-mal fat and linseed oil fatty acid methyl esters (LSME), theirinter-mixtures and their mixtures with fossil diesel fuel.

The aim of our work was to determine the biodegrad-ability of various kinds of methyl esters and their mixtureswith fossil diesel fuel in natural environments.

2 Materials and methods

The materials used for the research are the following:

Fossil diesel fuel, which met the requirements of thestandard EN 590:2004 “Automotive fuels – Diesel –Requirements and test methods”.

Dichloromethane, analytically pure (Merck).

RME, which were obtained when refined rapeseed oil wastransesterified twice by rectified methanol, 99.9%. Thealkaline catalyst, KOH, was used in the process. Theproduct met the requirements of the standardEN 14214:2001 “Automotive fuels – Fatty acid methylesters (FAME) for diesel engines – Requirements and testmethods”.

REE, which were obtained when refined rapeseed oil wastransesterified twice by anhydrous ethanol. The alkalinecatalyst, KOH, was used in the process. The product metthe requirements of the standard EN 14214:2001.

LSME, which were obtained when linseed oil was trans-esterified twice by rectified methanol (99.9%). The alka-line catalyst, KOH, was used in the process.

Tallow fatty acid methyl esters (TME), which wereobtained when beef tallow was transesterified twice byrectified methanol (99.9%). The alkaline catalyst, KOH,was used in the process.

Lard fatty acid methyl esters (LME), which were obtainedwhen pork lard fat was transesterified twice by rectifiedmethanol. The alkaline catalyst, KOH, was used in theprocess.

Some quality parameters of the tested biodiesel fuelsamples are demonstrated in Tab. 1.

The biodegradability of the fuels and their mixtures wasdetermined following CEC L-33-T-82 “Determination ofbiodegradability of fuel in water”. The analysed fuels weredissolved in carbon tetrachloride (150 g/L) and preparedin accordance with CEC L-33-T-82 methodology.

The methodology recommends taking bacterial material,which contains at least 106 CFU/mL (CFU – colony form-ing unit) of bacteria. This is reached when the eluent isused after the first stage of cleaning (mechanical) of localwastewater treatment equipment. It was decided to useeluent from PLLC “Kaunas Water”. The amount of bac-teria determined by the Dip Slide test met the require-ments. Before incubation, the bacterial material was keptfor not longer than 48 (sampling time included) at a tem-perature of 16 7C.

After the incubation time was over, the fuel was extractedfrom the samples and the extracts were analysed by themethod of infrared spectroscopy using the FT-IR spec-trometer Spectrum GX (PerkinElmer). The measurementparameters are the following: resolution –1 cm–1, scan-ning rate –0.2 cm/s, number of scans 20, strengthening–1. The data were processed with the help of the Spec-trum programme. The presented results are the averageof three measurements of test samples prepared from thesame test material.

Tab. 1. Quality parameters of biodiesel fuel samples.

Parameter RME REE LSME TME LME Test method

Ester content 98.8 97.6 98.1 97.8 97.2 EN 14103Monoacylglycerol content [%] 0.51 0.72 0.55 0.68 0.77 EN 14105Diacylglycerol content [%] 0,12 0.18 0.15 0.17 0.18 EN 14105Triacylglycerol content [%] 0.04 0.06 0.06 0.08 0.10 EN 14105Free glycerol [%] 0.01 0.01 0.01 0.02 0.02 EN 14105Oxidation stability, 110 7C (Rancimat test) 6.32 6.50 0.49 0.44 0.38 EN 14112


Eur. J. Lipid Sci. Technol. 109 (2007) 493–497 Biodegradability of biodiesel fuel 495

3 Results and discussion

According to a literature analysis, the biodegradability ofanimal fat and LSME and their mixtures has not beenpreviously examined. The composition of animal fat fattyacid methyl esters is different from vegetative fatty acidmethyl (ethyl) esters, where the number of saturated acidsis 6–8 times greater.

A comparative research on the kinetics of the biodegrad-ability of RME, REE, pork LME, TME, LSME, and fossildiesel fuel was carried out in accordance with the above-mentioned methodology. The dynamics of biodegrad-ability is presented in Figs. 1 and 2.

During the standard period of 21 days, 94.2% of REE and91.2% of RME were degraded, while the degradability offossil diesel fuel was just 57.3%. The research on fossildiesel fuel was continued, and it was determined thatduring the period of 80 days the degradability was just64.7%. According to our results, the biodegradability inwater of REE is higher than that of RME.

The obtained results of our research of RME biodegrad-ability confirmed the data published in the European liter-ature [1]. The results of American scientists concerning

Fig. 1. Dynamics of biodegradability of fuel: (m) RME,(XI ) REE, (n ) D.

Fig. 2. Dynamics of biodegradability of fuel: (m) LSME,(XI ) LME, (n ) TME.

the biodegradability of REE, RME and fossil diesel fuel,which were obtained by applying the research methodol-ogy of measuring CO2, are different from the data we havereceived. They have shown that there is a somewhatlower biodegradability of (89%) RME and (87%) REEduring a longer period than that required in the EU docu-ments, i.e. 28 days. The degradability of fossil diesel fuelduring this period hardly reaches 18%, according to thescientific data [5].

Fig. 2 presents the data on the biodegradability ofLSME, LME and TME. During the period of 21 days,98.3% of LSME, 90% of TME, and 92.5% of LME weredegraded. The biodegradability rate among animal fattyacid methyl esters is very similar; only LME degradesslightly more quickly. The best characteristics of biode-gradability may be attributed to LSME. The biodegrad-ability of LSME reached the requirements set forrenewable fuel in 14 days, while in 21 days 98.3% ofLSME was degraded.

The characters of the biodegradability curves of LME andTME are very similar. The degradation of fatty acid methylesters of animal origin is higher than that of methyl estersof vegetable origin. As much as 72.4% of LME and 69.4%of TME degrade within 6 days; later, the process of bio-degradation becomes slower. The character of the curveof LSME biodegradability is almost rectilinear until the14th day, and from the 15th day the biodegradationbecomes significantly slower (Fig. 2). It is possible tostate that fatty acid methyl esters of animal origin do nothave natural antioxidants (the oxidation stability of purefatty acid methyl esters is demonstrated in Tab. 1); there-fore, their initial degradability is higher under aerobicconditions, whereas vegetative esters degrade due tounsaturated links after the activity of antioxidants hasstopped.

We also investigated the conformity of mixtures of animaland vegetative methyl esters to the requirements ofstandard EN 14214. We determined optimal concentra-tions of RME-LSME-LME mixtures, whose iodine values,linolenic acid contents and oxidation stabilities met therequirements of the standard [13, 14].

The dynamics of biodegradability for mixtures consistingof optimal concentrations of RME-LSME-LME is pre-sented in Fig. 3. The biodegradability of multi-componentbiofuels (RME-LSME-LME) is compared to the degrad-ability of fossil diesel fuel.

The biodegradability of multi-component biofuels con-taining 90% RME, 2% LSME, 8% LME; 80% RME, 4%LSME, 16% LME; or 70% RME, 6% LSME, 24% LME is


496 E. Sendzikiene et al. Eur. J. Lipid Sci. Technol. 109 (2007) 493–497

Fig. 3. Dynamics of biodegradability of multi-componentbiofuels.

similar. After 21 days, the biodegradability of all multi-component biofuel is higher than 90% and is almost1.5 times higher than that of fossil diesel fuel. The mixturethat consists of 70% RME, 6% LSME and 24% LMEshows the best biodegradability. This multi-componentbiofuel was chosen for the subsequent research on bio-degradability, when mixed with fossil diesel fuel (Fig. 4).The results of the assessment of biodegradability after21 days are presented. For comparison, the RME mix-tures with fossil diesel fuel were investigated. During theperiod of 21 days, the mixtures containing multi-compo-nent biofuel were degraded better than those which con-tained pure RME. The mixtures containing 25% multi-component biofuel or RME and 75% fossil diesel fueldegraded by more than 84%; however, they do not meetthe requirements set for renewable fuel. The tendencyshows that the biodegradability of the mixtures should behigher than 90% if the mixtures contained more than 35–40% of multi-component biofuel or RME. It is possible tostate that the biodegradability of fatty acid methyl estersand fossil diesel fuel is not an additive value, and evensmall additions of fatty acid methyl esters or their mix-tures to fossil diesel fuel significantly improve the biodeg-radability.

Fig. 4. Biodegradability of biofuel and fossil diesel fuelmixtures after 21 days: (u) D-RME, (n ) D-FAME (FAMEcomposition: 70% RME, 6% LSME and 24% LME).

4 Conclusions

(1) The fatty acid methyl esters meet the requirements setfor fuel biodegradability by the EU. During the period of21 days, 91.2% of RME, 94.2% of REE, 98.3% of LSME,90% of TME, 92.5% of LME, and only 57.3% of fossildiesel fuel were degraded.

(2) The biodegradability of multi-component biofuelscontaining 90% RME, 2% LSME, 8% LME; 80% RME,4% LSME, 16% LME; or 70% RME, 6% LSME, 24% LMEis similar; the best biodegradability is that of the mixturemade up of 70% RME, 6% LSME, and 24% LME. After21 days, the biodegradability of all multi-component bio-fuels was higher than 90% and about 1.5 times greaterthan that of fossil diesel fuel.

(3) The mixtures of multi-component biofuel and fossildiesel fuel degrade by more than 90% within 21 dayswhen they contain 35% or more fatty acid methylesters.

Acknowledgments

The research work was carried out within the frame-work of the EUREKA programme. Authors are thankfulto the Lithuanian Science and Studies Foundation forsupport.

References

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[Received: November 3, 2006; accepted: February 1, 2007]


biodegradability of biodiesel fuel of animal and vegetable origin

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