The up to date standard for pure Bioethanol is the EU standard EN 15376:2011. An American standard ASTM D 4806 also exists. Under this standard there are a number of parameters that the bioethanol must meet. These include a minimum percentage of pure bioethanol and maximum water, methanol, acidity, copper, phosphorus and sulphur contents to include just some of the impurities that are commonly found in bioethanol. Exceeding the permissible limits can lead to numerous problems in the automobile.

In Ireland, the bioethanol generally sold in the forecourts is blended with petrol; commonly either a blend of 5% bioethanol (E5) with 95% petrol or 85% bioethanol (E85) with 15% petrol. The E5 blend must meet an adapted version of EN 228 petrol standard that allows for 5% bioethanol. The E85 blend must meet ASDM D 5798 standard.

We have encountered two major problems with bioethanol blends sold in Ireland: the first relates to the bioethanols’ affinity with water – when petrol containing bioethanol comes in contact with water, the latter leaches out the ethanol and forms an aqueous layer at the bottom of a tank. Motor vehicles taking on this fuel can stop a short distance from the garage. Generally, the garages around Ireland haven’t yet adapted to the more stringent hygiene (excluding water) that the bioethanol petrol requires.

The other problem most encountered with bioethanol blends is the increased vapour pressure of the petrol. The vapour pressure of unblended petrol is usually at its permissible maximum. Addition of bioethanol causes a spike in the vapour pressure and this can lead to air-locking problems.

We would recommend analysis on the final product as a rule but if changing supplier or if previous problems have occurred, we can test the pure bioethanol to check it is of adequate quality for blending.