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QLK5-2000-00533
BIOSTAB: Stability of biodiesel |
| Contract No: | QLK5-2000-70230 | ||||
| Source: | Final Report
| Source: |
Second Annual Report - March 2003
| Source: |
First Annual Report - March 2002
| |
The final results were presented at a workshop held in Graz in July 2003 and published in October 2003 as:
 | Stability
of Biodiesel used as a Fuel for Diesel Engines and Heating Systems Presentation of the BIOSTAB Project Results ISBN 3-902451-00-0, 82pp. 2003 - published by BLT, Rottenhauser Strasse 1, AT-3250, Austria, price 20 euro including postal charges. Order by email from: elfriede.heiden@blt.bmlfuw.gv.at.
Introduction Introduction to the BIOSTAB project Biodiesel has become a rapidly growing market of renewable biofuels in the European Union. Especially the substantial expansion of the production capacity in Germany requires special attention and special measures for the market adaptation. The European biofuel directive (2003/30/EC, published in May 2003) serves as another impetus to the development. In order to ensure customers' acceptance, standardisation and quality assurance are key factors in the market introduction of biodiesel. In 1997 the European Commission gave a mandate to CEN to develop standards for biodiesel as a transport and heating fuel. Minimum requirements and test methods are included in the forthcoming standards, prEN 14214 (Biodiesel as automotive diesel fuel) and prEN 14213 (Biodiesel as heating fuel). However, during the standardisation process major significance was attached to fuel stability. In 2001 the European project 'Stability of Biodiesel' (BIOSTAB) was started in order to obtain information on this very important topic. The main objective of the project is to establish criteria and corresponding analytical methods to determine the stability of biodiesel. In detail the project aims are:
Nine experienced partners from industry, science and research were involved in the project. 7 out of 9 partners were members of one or more CEN working groups during the Biodiesel standardisation process. All partners have specific and long-term biodiesel experience. The working programme was divided into four work packages. For each work package (WP) a work package leader had to co-ordinate the tasks between the several partners. An overview of the content of the work packages is given below:
By *Florence Lacoste, *Lionel Lagardere and **Paolo Bondioli *ITERG (France), **SSOG (Italy) The objectives of the work package are to evaluate and/or develop accurate methods for determination of oxidation, storage and thermal stability. Three items referring to behaviour of biodiesel submitted to oxidative conditions have been defined by the CEN working group in charge of specifications in the execution of Mandate M/245, depending on the uses of biodiesel Oxidation stability (presence of oxygen): although ISO 6886 (Rancimat test) has been chosen in the execution of Mandate M/245 as the test method for thermal oxidation stability, it has to be to clarified the relationship between the induction period provided by this test and other quality parameters. Indeed, this test is unfavourable to distilled biodiesels compared to undistilled products without correlation of experience on the field. Thermal stability (absence of oxygen) and storage stability: Due to a lack of knowledge no test method has been chosen for these two items in the execution of Mandate M/245. One of the main goals is to select a method for each item (already existing or new) considering criterions such as reflection of real conditions, correlation with quality parameters of biodiesel, precision, cost. Conclusions Oxidation stability: Rancimat test (pr EN 14112) was evaluated for seven biodiesel samples (Methyl ester from rape seed oil, sunflower oil, used frying oil and tallow). Determination of quality parameters was carried out on aliquot samples along every each % hour. All parameters present a visible variation along the Rancimat test except UV 270 nm. At the end of Rancimat induction period, the samples do not meet FAME or Oils and Fats specifications such as viscosity, acid value, ester content or peroxide value. Rancimat induction period is well correlated to induction period given by quality parameters, but Rancimat induction period is almost 10 % higher than induction period given by quality parameters. Main conclusion is that induction period determined by conductivity is well correlated to degradation of quality parameters along Rancimat test. Storage stability: At the beginning of the project it was decided to evaluate two test methods. The first one is the petroleum field reference method (ASTM D4625 storage at 43oC during 24 weeks), the second one corresponds to an accelerated IP48/IP306-like method at 90oC with an airflow above the surface of the sample. For each test method, a list of seven quality parameters was defined. Critical review of evaluation storage stability with ASTM D4625 was carried out. Because it was difficult to make a correlation between ASTM D 4625 and results of accelerated method initially proposed (accelerated 1P48/1P306-like method at 90oC), it was decided to use Rancimat apparatus, specially modified for storage stability evaluation. A stream of purified air (101/h) is passed above the surface of 3 grams of sample heated at 80oC during 24 hours. Then peroxide value, ester content and polymer content are measured. The modified Rancimat test is suitable for use in terms of repeatability, significance and it is easy to handle. Peroxide value determination shows the best correlation with ASTM D 4625 (storage at 43oC during 24 weeks). Using this method 'low stability' a nd 'high stability' samples can be separated. Thermal stability: At the beginning of the project it was decided to keep the ageing conditions of ASTM D 6468 (150oC, 180 or 90 minutes) as they were considered not too far from the real conditions. A list of seven quality parameters to be looked at before and after the test, was defined, But the variation of quality parameters (acid value, Rancimat, ester content) after the ageing test was too low to be measured correctly. Thermal stability tests at 200oC (oil bath) during 5 hours showed that samples coming from European productions are really stable when heated at high temperature in absence of air flow. Viscosity and acid value were chosen to evaluate the ageing effect. But the repeatability of results were not acceptable. So, it was decided to use Rancimat apparatus with a procedure specially modified for thermal stability evaluation. Eight grams of sample are aged for 6 hours at 200oC in open tubes with air exposure. After ageing and cooling, polymer content is determined by HPLC. The modified Rancimat test is suitable for use in terms of repeatability and it is easy to handle.
By *Paolo Bondioli, *Ada Gasparoli, *Laura Della Bella, *Silvia Tagliabue, *Guido Toso, **Andreas Frohlich and ***Jurgen Fischer *SSOG (Italy), **TEAGASC (Ireland), ***OLC GmbH (Germany) Objectives The main objective of this work package was to carry out a systematic study of the changes occurring in biodiesel samples, prepared using different feedstock and different production technologies, during a long term storage experiment in real conditions. For each sample 15 parameters were monitored periodically. After the results became available of a questionnaire issued by WP1 regarding the common storage conditions of biodiesel in practice, storage tests in presence of direct light and at temperatures higher than ambient temperature were discarded. Major emphasis was devoted to the study of storage behaviour of samples including additives. Another objective of this work package was the contemporary preparation of a relevant amount (> 100 litres) of biodiesel samples obtained from different feedstock and aged under normal conditions. These samples were supplied to WP 4, in order to study the fuel behaviour. All tests were carried out only after assessment of biodiesel quality, according to the European biodiesel standards prEN 14213 and prEN 14214. Minor deviations from the specification limits were tolerated in order to have a wider spectrum of different samples under ageing. Several control samples with no additives did not fulfil the requirement for oxidation stability, but this fact was expected because in most cases additives are necessry.Some previous studies about biodiesel storage have been published in the past and these represented the starting point for the activity. More recently a study about an accelerated storage test carried out at 43 oC in controlled conditions was published by this group [Eur. J. Lipid Sci. Technol 104, 777-784, 2002]. Conclusions After consideration of all the experimental results the following conclusions were reached:
By Sigurd Schober, Martin Mittelbach University Graz (Austria) Work package 3 dealt with the evaluation of the effects of synthetic and natural antioxidants on the oxidation stability of biodiesel. Within the European specifications the value for the oxidative stability, expressed as the induction period using a Rancimat instrument, has to be higher than 6 hours and should be guaranteed during the whole supply chain of the fuel. However, the stability of biodiesel varies significantly depending on the feedstock as well as the process technology. Biodiesel produced from rapeseed oil showed higher induction periods, whereas biodiesel produced from used frying oil, sunflower oil, soybean oil or animal fat had similar or significantly lower values for the induction period. A reason for this is the different fatty acid composition among the feedstocks and of course, the different content of natural antioxidants which prevent vegetable oils as well as the remaining esters from oxidative degradation. Also, distilled biodiesel, which has the highest purity from the chemical point of view, has a very low oxidative stability due to the lack of natural antioxidants, which had been removed during the distillation. Therefore, in future most of the biodiesel produced will have appropriate antioxidants added. Because of this different commercially available natural and synthetic antioxidants were tested in order to improve the oxidative stability of biodiesel. Furthermore the influence of the most effective antioxidants on specific parameters, existing in the international specifications for biodiesel was investigated, in order to find appropriate additives to improve oxidation stability without deterioration of the other parameters. Finally a screening of the most promising antioxidants was performed to evaluate the optimum antioxidant amount. Conclusions The influence of different antioxidants on the oxidative stability of biodiesel prepared from different feedstocks was investigated. The results can be summarised as follows:
WARNING: The present paper does not include any recommendations for the use of specific antioxidants. Long term engine tests have to be carried out in order to study the influence of synthetic antioxidants on engine performance.
By Andras Frohlich TEAGASC (Ireland) To investigate the influence of natural antioxidants on the oxidation stability of fuel grade biodiesel. Conclusions Tocopherols alpha-, delta-, and gamma- delay the oxidation of SME, RME, WCOME and TME, in some cases by more than a factor of 10 compared to methyl esters without tocopherols. Gamma-tocopherol was found to be the most effective of the three, alpha-tocopherol the least, and their antioxidant effect increased with concentration up to an optimum level. Above the optimum level the increase in antioxidant effect with concentration is relatively small. The stabilising effect of tocopherols was also found to depend on the composition of the methyl ester, the order of effectiveness was found to be: TME>WCOME>RME>SME Oxidation of methyl esters begins with the build-up of peroxides: viscosity starts to increase only after the peroxides reach a certain level. Tocopherols stabilise the methyl esters by reducing the rate of peroxide formation, thereby extending the time needed to reach the peroxide level where viscosity starts to increase. The carotenoids astaxanthin and retinoic acid had no detectable effect on the stability of SME. Similarly beta-carotene added to CME along with some alpha-tocopherol, to give the same maximum absorbance at 448 nm as RME, had no stabilising effect on the methyl ester. However a carotenoid, at much higher level than beta-carotene, was detected in RME, but it was not present in less stable methyl esters such as CML and SME. The effect of the detected carotenoid on the stability of RME is being investigated.
By Jurgen Blassnegger, TUG (Austria) The aim of WP 4.1 is the investigation of the effects of fuel stability on diesel engines and injection systems. Several fuels with varying stability was used in bench and field tests. Tests were carried out on vehicles and vehicle injection systems. The results of the tests should help to find a relationship between laboratory test methods and effects of low stability during use. Conclusions Long term tests were carried out with 3 different modern injection systems on the test bench. Three fuel qualities, rape seed oil methyl ester with a low, a standard and a high stability were used. The fuels were tested in a long term test in 3 different modern injection systems. Wear and sedimentation were analysed after the tests. Chemical analysis of the fuels accompanied the tests. The injection systems were examined for wear and sedimentation and found to be normal for the runtime. Observed effects were more apparent in those parts which were operated in test runs with fuel with the lower oxidative stability. Fatty deposits could only be detected on system parts which were operated in the test run with extreme conditions (RME low oxidation stability, no change of the fuel during the complete test run at the injection system test bed). At all other systems no critical sedimentations could be detected. Two long term real world engine tests were carried out on the test bench fuelled by biodiesel with a low and a high stability. The direct injection diesel engine were equipped with a modern common rail injection system. The test duration at each test was 500 hours, using both high and low oxidation stability RME. The measured differences in emissions and power between diesel- and RME-operation at the begin of each test were normally for biodiesel use. The power loss and the different in the injection amount after a 250-hour run-time were higher than expected. The analyses of the test run engines show that the abrasion was normal for a 500-hour runtime and no significant difference to diesel operation was noticed.
By *Heinrich Prankl, *Hermann Schaufler and **Jürgen Blassnegger *BLT (Austria), **TUG (Austria) Low stable Biodiesel containing ageing products may cause problems during use in sophisticated fuel injection systems. Thus, a fleet test was carried out with different vehicles and injection systems. The objective of the test was to determine possible effects of a low stable biodiesel used in vehicles. Conclusions
Four passenger cars were operated in a fleet test with a low stable biodiesel from July 2001 to
November 2002. The test fuel was pre-aged by a special treatment with temperature and air. The
oxidation stability determined by the induction period (Rancimat, 110oC) could be
reduced from 7 hours to <2 hours. Two cars were equipped with a fuel distribution pump, the
other cars with a pump injector system. The passenger cars were used in typical operation, mainly
on the motorway. Distance and fuel consumption were recorded. Temperatures (engine oil, fuel filter,
fuel tank, ambient) were recorded automatically during the whole test period. The total driving distance
ranged from 21000 to 60000 km per car. Initial and final tests were carried on a roller test bed. The
tests comprised performance and exhaust emission analyses (CO, HC+NOx, particles).
The differences in emissions and performance could not be assigned to the biodiesel operation
(in combination with the results of the injection system check after the test run). The diesel measurement
at the end of the biodiesel field test can only be assessed to a certain extent (short conditioning time).
Before and after the field test all limited emissions were below the EURO 3 level (EURO 3 limit vehicle
group 2, 1305 kg
In a 19 months fleet test run with 4 diesel vehicles (light duty LU: heavy duty HO) the performance
of a diesel fuel (EN 590) blended with 5% UFOME (used frying oil methyl ester) was evaluated.
Parameters controlled regularly during the test were:
Conclusions
The objective of this work package was to investigate the effects of fuel stability when used in
heating systems. The effects of the fuel stability during the application and the operation parameters
of the residential heating system using blended fuels were studied. Bench and field tests were carried
out on different heating systems. The results helped to establish relationships between laboratory test
methods and experimental results obtained during use as heating fuel.
Conclusions
In general the bench tests in the start up mode showed two different types of result depending
on the operation mode of the heating system: stationary or non stationary conditions. Under
stationary conditions the emissions are as low as expected and all units fulfil the general standards
for heating units. However during the starting procedure of the heating unit (medium warm start - non
stationary condition) the concentration of the hydrocarbons and the carbon monoxid in the flue gas
were higher than some seconds after the start. These irregularities depend very much on the technology
of the heating units. Additionally, these heating systems having high emissions during the starting process
show worse CO and hydrocarbon emissions with increased FAME percentage in the blend.
In the long term test of three different heating units with different fuels one fact can be seen clearly.
The blends made from FAME products with a critical stability (aged artificially, stored for 1 year or
distilled and stored for 1.5 years) caused problems in the oil feed rate counter.
Progress Report Summary
Introduction
Standard and quality assurance are key factors for customer acceptance of biodiesel as a transport
or heating fuel Minimum requirements for composition and quality as well as test methods are are
included in the proposed standards for biodiesel. However, during the development of such
standards fuel stability was recognised as a key parameter and detailed research is needed in this area.
Objectives
The objectives of the project are to establish criteria and the corresponding analytical methods to
determine the stability of biodiesel. The aims are:
Determination methods:
Oxidation stability: The Rancimate test (prEN 14112) was evaluated using rapeseed, sunflower,
tallow and used frying oil methyl ester, both distilled and un-distilled. The oxidation curves obtained
during the Rancimate (conductivity) test were compared with those obtained by measuring the variation
of oxidation parameters against time (peroxide value, anisidine value, kinematic viscosity, ...). The main
conclusion is that the induction period determined by conductivity is closely correlated to the
degradation of quality parameters.
Storage stability: Because it was difficult to correlate ASTM D 4625 (storage at
43 oC during 24 weeks) with an accelerated method initially proposed (accelerated
1P48/lP306 - like method at 90 oC), it was decided to use the Rancimate apparatus,
specially modified for storage stability evaluation. The test is suitable for use in terms of repeatability,
significance and it is easy to handle. Peroxide value determination shows the best correlation with
ASTM D 4625.
Thermal stability: Thermal stability tests at 200 oC (oil bath) during 5 hours
applied to all samples collected for WP1 demonstrate that samples coming from European productions
are really stable when heated at high temperature in absence of air flow. It was decided to use
Rancimate apparatus with a procedure specially modified for thermal stability evaluation. The test
seems to be suitable for use in terms of repeatability and it is easy to handle.
Storage tests
The storage test using eleven drums of biodiesel from different sources (methyl ester made from
rapeseed, sunflower, used frying oils and tallow) could be completed in autumn 2002. 200 litre drums
of biodiesel were stored under different conditions. Samples were taken out periodically and different
quality parameters were monitored. The data were used for developing the method for the determination
of storage stability. 7 drums were provided to carry out bench tests at University of Technology in Graz.
Antioxidants
Based on the first overview the literature survey was updated with new material. Until now the literature
work includes 106 articles of recent literature and will be updated until the end of the project. The
solubility of antioxidants even at low temperatures was checked. Furthermore the most promising
antioxidants out of the screenings were investigated concerning their behaviour when blended with
fossil diesel in different ratios. Out of the screenings the optimum antioxidant concentration of most
effective antioxidants was evaluated. The determination of the influence of those antioxidants on
biodiesel quality was finished.
The effect of natural antioxidants on the stabilities of methyl esters from rape seed oil (RME), sunflower
oil (SME), used frying oil (UFOME) and tallow (TME) was evaluated. The results indicated that
tocopherols have a stabilising effect on biodiesel, and alpha is much less effective than delta which in turn is
less effective than gamma. The stabilising effect of the tocopherols depends also on the composition of the
methyl esters, and the order of effectivity of delta-tocopherol was found to be TME>UFOME>RME>
SME, Astaxanthin and retinoic acid had no effect on the stability of the methyl esters tested.
Use of biodiesel as automotive diesel fuel
Six of seven long term injection tests using FAME with a low, a standard and a high fuel stability
have been completed so far. The investigations involved the following injection systems:
Two long term tests were carried out with a 1.400 litre passenger car diesel engine, turbocharged
and equipped with a common rail injection system. FAME with a high and with a standard stability
were used.
A fleet test using FAME with a low stability as the only fuel was completed. Exhaust emissions and
engine performance were measured on a roller test bed. The injection systems were removed and
returned to the FIE manufacturers for inspection and comment.
The vehicle field test programme with a 95% fossil diesel/5% FAME blend was continued during
the 2nd project year. Exhaust emission tests were carried out in March and September/October 2002.
The fijel supply chain was inspected in order to detect fuel residues or deterioration. Further fuel
influence on the engine oil was checked by sampling every 5000 km.
Use of biodiesel as heating fuel
Conclusion
Different methods for determining the thermal and storage stability of biodiesel can be proposed
on the basis of the results obtained by the end of the project. The best method for determination the
oxidation stability was verified. FAME samples from European producers have shown a high stability
at various temperatures in the absence of air. A number of promising antioxidants are available that
vary in their suitability. The final results of bench tests and practical tests will be available after
completion of the final inspection of the systems used.
Benefits and Beneficiaries
The experimental results obtained in this project increase the understanding of factors affecting the
stability of biodiesel. A more stable product will boost customer confidence in this renewable liquid
biofuel and improve its market share.
Progress Report Summary Objectives Biodiesel has become a fast growing renewable liquid biofuel within the European
Community. In order to ensure customers acceptance standardisation and quality
assurance are key factors in the market introduction of biodiesel as a transport
and heating fuel. In 1997 the European Commission gave a mandate to CEN to develop
standards concerning minimum requirements and test methods for biodiesel. It
turned out that one key parameter, fuel stability, had been overlooked. Hence,
detailed research is needed in this area. The objective of the project is to
establish clear criteria and corresponding analytical methods to be used to
determine the stability of biodiesel. The detailed objectives are to develop:
Activities So far nine experienced partners from industry, research institutes and universities
representing biodiesel research in Europe are involved in the project. The work
programme is divided into four work packages: WP1: Determination methods: The objective is to evaluate
and to develop accurate methods for the determination of the extent of oxidation
in storage and thermal stability. Data was collected from biodiesel storage
experiments and from automotive sources and it will be used to develop analytical
methods. The method for oxidation stability (Rancimat test which was already
fixed by CEN) could be correlated with different quality parameters. Promising
methods for the determination of thermal and storage stability were proposed
and are being evaluated and improved at present. WP2: Storage tests: A storage test using eleven drums
of biodiesel from different sources began in July 2001. Methyl ester made from
rapeseed, sunflower, used frying oils and tallow was stored in 200 1 drums under
different conditions. Samples were taken out periodically and different quality
parameters monitored. The data will be used for developing the method for the
determination of storage stability. After completing the first storage year
some samples will be used for bench tests. WP3: Antoxidants: Based on the findings of an extensive
literature survey twenty synthetic antioxidants were selected, all of which
are commercially available at an affordable price. The stabilising effect of
the selected antioxidants was tested with biodiesel prepared from four different
raw materials (RME - rapeseed oil methyl ester, SME - sunflower oil methyl ester,
UFOME - used frying oil methyl ester and AFME - animal fat methyl ester). Both
distilled and undistilled biodiesel samples were tested. Rancimat induction
times were used to indicate oxidation stabilities. Antioxidants with good stabilising
effect were tested at different concentrations in order to determine the optimum
antioxidant levels. The effect of natural antioxidants on the oxidation stability
of biodiesel was also evaluated. The relatively high stability of RME which
cannot be attributed to the detected natural antioxidants is being investigated. WP 4: Utilisation of biodiesel: This workpackage was divided
into two parts. Field test programme: Eight test facilities were installed
in Lower Austria. The heating systems were selected in agreement with the owners
of system (one family households) and the burner and boiler manufacturers. Rape
seed oil methyl ester and used frying oil methyl ester were used in blends of
5% with mineral diesel heating fuel. Four of the eight systems were operated
with fuel stabilised by antioxidants. Fuel analyses was carried out periodically.
The operating parameters (temperatures, pressures, operation times) were recorded
automatically. Discussion Different methods for determining the extent of oxidation, thermal and storage
stability of biodiesel can be proposed. The results of long term storage tests
will give us a better understanding of the effect of the chemical composition
on the stability of biodiesel. Several antioxidants were found to stabilise
biodiesel, but they have not been fully evaluated yet. Bench and car fleet tests
have started already, but results will not be available before completion of
the tests. The experimental results which will be obtained in the present project, will
improve greatly our understanding of the stability of biodiesel. With better
understanding it will be possible to recommend the inclusion of relevant stability
parameters in the biodiesel standard. A more stable product will boost customer
confidence in this renewable liquid biofuel and improve its market share. Therefore
it will help to achieve the goals set out in the 'White Paper for a Community
Strategy on Renewable Sources of Energy" and in the "Campaign for Take-Off". © Copyright 2006 Policy Statements |
