Disposal and selection of rapidly biodegradable hydraulic oils

Year of publication: 2009


More than 20% of lubricants are not recycled. They leak into the ground or the water and disappear, they form films on components, or they remain in decommissioned machinery. In some cases, incorrect disposal results from inadequate information. In this regard, the impression suggested by the term “bio-oil”, supported by the “Blue Angel” or the European daisy symbol, is enormously deceptive. Even oils with this designation should not end up in the environment. Users often think that as long as they use rapidly biodegradable hydraulic fl uids, they do not have to take any action if a fairly large volume of hydraulic fluid ends up in the environment (soil or water). Using these synthetic fluids does not free users from the obligation to inform the authorities of environmental spills and to remove the fluid from bodies of water or polluted soil. Furthermore, simply allowing hydraulic fluid to drain into the ground when the fluid is changed is entirely out of the question, even with “bio-oils”.

Lubricant disposal is regulated by law, such as the Altölgesetz (Waste Oil Act) in Germany. Bio-oils are not exempted. They are treated in the same way as corresponding synthetic oils or mineral
oils. Rapidly biodegradable, environmentally compatible oils should be used by preference for work in environmentally sensitive areas. The storage of working materials is regulated by classifying
them according to their water hazard. Rapidly biodegradable, environmentally compatible oils are usually classified in water hazard class WGK1.

Prüfverfahren, mit denen beurteilt werden kann, was ein „Bioöl“ ist, gibt es viele, nicht nur länderspezifisch! Doch nicht alles, was getestet wird, ist wirklich aussagekräftig. Für Hydrauliköle kann im Allgemeinen die von einem internationalen Normengremium verabschiedete ISO 15380 für umweltverträgliche Druckfl üssigkeiten herangezogen werden. In den dieser Norm zugrunde liegenden Tests nach ISO 9439 oder ISO 14593 wird die Abbaubarkeit des Öls, so wie es im Fass oder in der Maschine ist, getestet. Ob das „fertige“ Öl auch den OECD-301x-Test besteht, wird aber nicht getestet. Bioöle auf der Basis von Polyalfaolefi nen (PAO), die nach der ISO 15380 dem Typ HEPR zuzurechnen sind, enthalten als Hauptkomponenten synthetische Kohlenwasserstoffe.

There are many test methods for determining whether an oil is a “bio-oil”, including tests thatare not specific to a particular country. However, not all of these tests actually produce reliable results. In the case of hydraulic fluids, the ISO 15380 standard for environmentally compatible hydraulic fluids, which has been adopted by an international standardisation organisation, can generally be used as a reference. The tests defined by ISO 9439 and ISO 14593, which form the basis for this standard, test the degradability of the fluid in the container or in the machine.
However, they do not test whether the “exhausted” fluid will pass the OECD-301x test.

Eco-oils based on polyalphaolefi n (PAO) that can be classified as HEPR in accordance with ISO 15380 have synthetic hydrocarbons as their primary ingredients. The commercially available environmentally compatible HEPR oils can also be rapidly biodegradable. As preformulated mixtures, they can also fullfil the requirements for rapid biodegradability specified in CEC-L-33-A-93. Many data sheets for hydraulic fluids and other lubricants state that they are rapidly biodegradable in accordance with CEC-L-33-A-93.
In other words, it is not absolutely necessary for an oil to pass the ISO 9439 or ISO 14593 tests for environmentally compatible fluids if it is not claimed to be compliant with ISO 15380.
The requirement for using bio-oils, which is often specified by public authorities in blanket terms in tender invitations without citing any standards, can be met by the CEC test, among others.
A few properties that make the long-term use of HEPR oils especially attractive were described in the Spring 2009 issue of ÖlChecker (pages 1 and 2).


When selecting a hydraulic fl uid for use in an environmentally sensitive area, proceed carefully and check the manufacturer’s specifications, the requirements of the equipment manufacturer, and
the regulations of the public authorities in detail. This way you will be on the safe side if anything untoward happens. If you change a system from a hydraulic fluid based on mineral oil to a rapidly biodegradable hydraulic fluid, always pay careful attention to the fluid conversion guidelines. Flushing procedures are necessary because the fluid volume in the tank is usually only around 30% of the total fluid volume. The mineral oil content must be less than 2% after the conversion. This can be checked with the OELCHECK bioset. A higher concentration of mineral oil can cause the bio-oil to lose its rapid biodegradability property.