Introduction to biodiesel additives
2nd May, 2008
Additives play a vital role in biodiesel production and storage, primarily for oxidation stabilisation and deposit controlBiodiesel stability is influenced by a number of factors including feedstock, the production process used and the amount of time the product spends in the supply chain.
Virgin oils that are fresh from the crusher are likely to be low in free fatty acids and subject to the pre-treatment stages. The fatty acid profile of the feedstock will have an important effect on overall stability with feedstocks high in poly-unsaturates tending to be less stable, such as soyabean, cottonseed and jatropha.
Distilled biodiesel has fewer tocopherols (natural occurring antioxidants) retained in the product than biodiesel produced in other processes, and biodiesel produced from hydrogenated feedstocks tend to be more stable.
Additive supplier SBZ explains that biodiesel can degrade due to a number of factors including:
- Oxidation from contact with air
- High ambient or storage temperatures
- Contact with water or moisture
- Storage times
Metal contamination such as copper and iron will catalyse the oxidative breakdown of unsaturated methyl esters and have a major impact on the oxidative stability.
The European standard for biodiesel EN14214 specifies minimum oxidation stability of 6 hours at 110°C. This is based on the EN14112 specification or Rancimat test.
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