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Biobased lubricants with convincing technical properties

The performance and application range of biobased lubricants is growing ever broader. Several biolubricants have been placed on the market, including plant-oil based products and synthetic plant-based lubricants. In this article, Rolf Luther from FUCHS EUROPE SCHMIERSTOFFE GmbH in Mannheim talks about the technical properties and potential application areas of biolubricants, some of which have been shown to be superior to conventional crude oil-based products.

Physicist Rolf Luther has been with Mannheim-based FUCHS, the world’s largest independent manufacturer of specialty lubricants, for more than 20 years and has been head of Test Fields and Advanced Development for around eight of those years. © private

Lubricants are needed everywhere – as engine oil in motor vehicles, as hydraulic oil in processing and other plants or as chain oil in chain saws. Liquid lubricants mainly consist of base oils and additives, the latter to impart performance characteristics to the lubricant. For example, lubricating grease consists of base oil and a thickener to achieve the required semi-solid consistency. 

Base oil can be produced by refining crude oil or from plants such as rapeseed. Chemical methods are subsequently used to further optimize the vegetable oils. This is achieved in a reaction called esterification, which involves combining an alcohol and the fatty acid contained in the oils to yield an ester plus water. These synthetic ester oils form the base for high-performance lubricants. It is also possible to introduce modifications in the fatty acid chains. The base substances used for the production of synthetic esters can be biogenic, i.e. produced from plant oils or animal fats. But they can also be derived from crude oil products,” says Rolf Luther, head of the FUCHS Group’s Test Fields and Advanced Development department.

Interestingly, the biobased synthetic ester oils are perfect for producing high-performance lubricants that are equal and sometimes also superior to conventional crude-oil based lubricants.

Biolubricants contain at least 25 percent renewable raw materials

“Initially, the only requirement of biolubricants was that they had to be readily biodegradable,” says Luther. Nowadays, it takes a bit more to be a biolubricant. The European Committee for Standardization’s (CEN) 2011 Technical Report (TR16227) requires biolubricants, which nowadays are referred to as biobased lubricants, to have the following characteristics:

•   The formulated product must have a carbon content derived from at least 25% renewable raw materials
•   Oils need to have > 60 percent degradation (fats > 50 percent degradation) within a defined time 
•   They must not be hazardous to the environment
•   They must meet specific technical performance criteria.

 

The European Ecolabel for Lubricants, also called “Euro-Marguerite”, has more stringent standards than the CEN, but applies to just a handful of lubricant groups. The lubricant’s hydrocarbon content derived from renewable resources, must be at least 45% for biogreases, 50% for biolubricants and as much as 70% for biobased total loss lubricants. Nowadays, biolubricants are also referred to as biobased lubricants. © RAL gemeinnützige GmbH

FUCHS is geared to the latest EU regulations. “The advantage of the EU Ecolabel scheme is that it requires companies to test the toxicity and biodegradability of the lubricant mixture rather than just the toxicity and biodegradability of individual components. The individual components often behave differently in a mixture than they do in pure form,” says Luther. This enables lubricant users to examine the professed environmental characteristics themselves. Luther also points out that modern users attach greater importance than ever before to uniform and comprehensible communication. “Which is why, in addition to the CEN’s definition of a biolubricant, the official EU Ecolabel, i.e. the Euro-Marguerite, is preferred over national product labels,” says Luther. “Standardization helps companies to better orient themselves on the market. The label is recognized throughout Europe and ensures that people understand biobased products in the same way,” says the expert. 

“There are very few products that cannot be produced with alternative materials”

In technical terms, the purely plant-oil based lubricants (e.g. rapeseed products) are only of limited use due to their susceptibility to temperature. This is not the case for products made from biobased synthetic esters. “Biolubricants generally have better lubricity, and therefore reduce friction and are better at preventing wear to moving parts. In addition, the biobased synthetic ester oils can be mixed with mineral oil at virtually any ratio and usually have a much better CO2 balance than their non-biological counterparts,” says Luther. As plant-oil products are not soluble in water, this means that when they leak into the environment, they are retained in the upper soil layer where, in contrast to crude-oil based products, they can be degraded and metabolized by microorganisms. “In contrast to mineral oils, biolubricants have a much higher viscosity index (VI). VI is a measure of the change in viscosity in relation to temperature. Additives are therefore not necessary to achieve a defined performance specificity, and it is also possible to produce much thinner oils,” says Luther. 

Biolubricants are primarily used in the same markets as non-biobased lubricants, e.g. forestry, agriculture and across the entire water sector with its offshore, harbour and sluice facilities,” says Luther. The substitution of mineral oils for biobased products has mainly been introduced in sectors and applications where recovery is almost impossible and where there is a high likelihood of them being discharged into the environment. Having said that, they are a long way off being used in all these sectors. “If it is technically impossible to prevent the oils from being discharged into the environment, in the event of leakage or the use of total loss lubricants, it is nevertheless desirable to reduce discharge as much as possible. The forestry sector has already identified the need for biolubricants, and in the future they will have to play a greater role in the agricultural sector as well,” says Luther.

“Biolubricants are possibly cheaper than traditional lubricants.”

The use of heavy equipment in agriculture leads to a considerable discharge of lubricants into the environment. © Michael Ottersbach/pixelio.de

“Biolubricants have a 3-4% share in the overall German lubricant market. In economic terms, the market for biobased products is extremely interesting, although in recent years it has not really been an expanding market,” says Luther, who believes that device specifications are a major reason for this. “Given existing market conditions, machine manufacturers make sure that the devices they develop will work first of all with standard mineral oils. In addition, many devices are only approved for a limited number of high-performance oils, which are of course also sold at an equally high price, even though a considerably cheaper bio-oil product would have been equally suitable,” says Luther. “The price-performance ratio of biolubricants is in fact more difficult to communicate.”

The price of biolubricants is in fact quite high. On average, vegetable-oil products cost twice as much as mineral-oil based products while synthetic biobased ester oils are three to five times more expensive. However, due to better performance and less wear, the application of these biobased products often leads to lower operating costs. However, Luther believes that people’s price-per-litre thinking still seems to win out. Germany is reacting to this by funding research and market introduction projects aimed at expanding sales opportunities for biolubricants. Useful backing also comes from the lubricant producers themselves who provide comprehensive advice and support in adapting devices to biolubricants. Modern biolubricants are technically mature and undergo continuous improvement; they are therefore likely to be used to a greater extent in future, especially with regard to environmental protection and sustainability.

Further information:
Rolf Luther
Head of Test Fields and Advanced Development 
FUCHS EUROPE SCHMIERSTOFFE GmbH
Friesenheimer Str. 19
68169 Mannheim
Tel.: +49 (0)621/37011777
E-mail: rolf.luther(at)fuchs-oil.de

Website address: https://www.biooekonomie-bw.de/en/articles/news/biobased-lubricants-with-convincing-technical-properties/