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Stability of biodiesel

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. Minimum requirements and test methods are included in the European standards for biodiesel. However, during the standardisation process a major significance was attached to fuel stability as one key parameter. In the project, the influence of storage conditions on fuel quality properties and the effects of natural and synthetic antioxidants will be investigated. A comprehensive test programme, including bench and field tests, will be carried out in order to investigate the effects of fuel stability during use.

The objectives of the project are to establish criteria and the corresponding analytical methods to determine the stability of biodiesel. These will be achieved by:
1) finding appropriate methods for the determination of stability under realistic conditions
2) understanding the influence of storage conditions on the quality of biodiesel
3) defining a minimum level of natural and/or synthetic antioxidants
4) determining the effects of the fuel stability during the utilisation of biodiesel as an automotive diesel fuel and heating fuel.

Progress to Date
Determination methods: The Rancimat test (method for oxidation stability) was evaluated for different biodiesel samples and tests for determining the thermal stability and storage stability were developed.
A one-year storage test with eleven biodiesel samples from different sources was performed and the development of different quality parameters was monitored.
Antioxidants: Twenty natural and synthetic antioxidants were tested on eight different biodiesel samples and the optimum additive concentration of the most effective antioxidants was evaluated.
Biodiesel as an automotive diesel fuel: Seven long-term injection tests using biodiesel with varying stability were carried out.
Biodiesel as a heating fuel: Start up tests, including functionality and emission measurements using conventional heating technology, were carried out with blends of fossil heating fuel, and 5% and 20% biodiesel.

Determination methods: The induction period determined by the Rancimat test was well correlated to the degradation of quality parameters along the ageing procedure. Thermal stability can also be determined by Rancimat.
Storage tests: With the exception of oxidation stability, all specification limits were met and no strong changes of quality parameters were found after a 12-month storage period. The Rancimat induction period decreases with time depending on the quality and storage conditions. The right additivation allowed the sample to fulfil the specification for oxidation stability for at least six months. Correct storage and logistics are necessary.
Antioxidants: The limit for oxidation stability was reached by the addition of antioxidants with all different types of biodiesel. The efficiency and the necessary amount of different antioxidants were strongly dependent on the feedstock and biodiesel production technology. No significant negative influence on fuel behaviour was observed.
Tests with biodiesel as an automotive diesel fuel: Concerning bench tests with injection systems and engines, functionality was given with all systems after the tests; also with fuels with a very low stability. However, the effects were found to be more salient at the parts of those tests with lower fuel stability. The field test with low stability RME was completed without problems but, after inspection, RME deposits could be found on parts of a distributor pump.
Biodiesel as a heating fuel - Bench tests: Non-stationary tests showed that emissions strongly depended on technology. Long-term tests: Two heating units were operated for 2 500 hours without any problems.


Scientist responsible for the project

Rottenhauser Strasse 1
3250 Wieselburg
Austria - AT

Phone: +43 7416 5217527
Fax: +43 7416 5217545


Project ID QLRT-2000-00533
Organisation Bundesanstalt für Landtechnik
Area 5.2
Start date 01 March 2001
Duration (months) 30
Total cost 1 389 715 €
Total EC contribution   958 891 €
Status Completed

The partners

  • SSOG - Stazione Sperimentale per le Industrie degli Oli e dei Grassi - Technology Dept., Italy - IT
  • Technische Universitaet Graz - Institut fuer Verbrennungskraftmaschinen u. Thermodynam., Austria - AT

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