Biodiesel and Side Effects
As Biodiesel becomes ubiquitous in fleet fuels, it's side effects are not well understood. Biodiesel has a wide range of adverse effects that operators should be aware of:
• Poor fuel economy as a result of lower energy content and consequently increased emissions.
• Increased engine deposition & reduced storage shelf life as a result of poor oxidative stability.
• Increased tank slimes and sludges from increased microbial growth and reduced fuel stability.
• Low temperature engine issues as a result of poor thermal stability.
• Reduced lube oil lifespan, incompatibility with elastomers and corrosive effects on engine components such as fuel pumps
Whilst there are many forms of Biodiesel, the most commonly found in mineral diesel fuels is FAME or Fatty Acid Methyl Ester. Depending on the fuel specification and country the content of FAME may be up to 20%. For example, in the UK the RTFO (Renewable Transport Fuels Obligation) changes the level of FAME in transport fuels periodically (please see section below).
One issue with FAME is that it is not homogenous; it contains different feedstock varieties (i.e. sewage, cooking oil, palm oil etc), ‘batch to batch’ differences, different storage practices and different production systems. Different biodiesel feedstocks produce different FAME components and different proportions of these components, even between batches of the same feedstock. Their make-up and effects on fuel quality characteristics are therefore unpredictable.