Products sold on the forecourt or to industrials comprise two major families of biofuel:
- with ethanol for petrol engines
- with FAME (Fatty Acid Methyl Ester) for diesel engines.
The proportion can be as much as 30%. For special uses there are also PVOs (Pure Vegetable Oils), animal fats and recycled food oils. In all cases it is important to ascertain the suitability of the product for the use. For instance, in a lorry engine, the fuel will be checked for minimum properties, the check being based on diesel specifications. In a boiler, the product is compared to domestic fuel. Bio-diesels are very prone to oxidation and sensitive to their storage conditions so, for instance, their stability regarding oxidation is checked.

Examples of available analyses:

Emission spectrometry to monitor the sulphur content in fuel and the presence of certain additives.

Water content to prevent distribution or high-pressure pumps from seizing up. Bio-diesels are subject to water "retention". Les Bio-diesels ont tendance à "retenir" l'eau.

Acidity (TAN) is measured to ascertain the risk of oxidation or abnormal contamination of the fuel.

Fuel filtering onto a membrane to observe through a microscope whether there are any external solid contaminants, often the cause of filter clogging.

Bacteria and fungi, micro-organisms which find all the conditions they need in diesel to develop swiftly and cause filter clogging and damage to injection systems. They are assessed by culture on agar.  

Iodine number:  This is a factor used to ascertain the origin of a vegetable oil (rapeseed, sunflower, oil palm, etc.). It is an EN 14214 requirement which is a characteristic of the FAME blended with diesel to form B5, B10, B30, etc... 

Infrared spectrometry to identify the fuel and measure the FAME or VOME (Vegetable Oil Methyl Ester) content.

Density which is often a sales measure for diesel because it is more exact than volume, so it is important for substantial bulk purchases.

Hexadecane number which represents a fuel's propensity to ignite. For bio-diesels with a high FAME content, only engine measurement is representative.

Ash content. This measurement is used to estimate the risk of unburnt substance production in the combustion process.