This is explained by Yijun Shi, Technical Director at Sustainalube AB, which develops and markets ecological oils and lubricants based on glycerol. The products began to be developed at Luleå University of Technology in connection with a scientific call concerning how to best make use of a major by-product generated during the production of what was then the new biodiesel, RME.
– It turned out that 1 kg of glycerol was formed for every 10 litres of biodiesel produced, and they wanted to find a useful application for such large quantities. Luleå University of Technology applied to the call with the idea of developing lubricants from glycerol.
Several times lower friction
The advantages were quickly discovered, and a Postdoc was hired to lead the research on the new ecological oil. Yijun Shi was recruited from China and has been part of the development ever since.
– During the first years, I carried out many tests and measurements and obtained figures showing that the friction of the new oil was 3–4 times lower than that of mineral oils, which is almost revolutionary. The glycerol-based oil is also water-soluble, which provides many environmental advantages. It contains no toxic substances and is food-approved, which means that if there is a spill in nature, no soil remediation is needed; the oil simply dissolves and is completely harmless to the environment.
Because the oil is water-soluble, it is also easy to wash off if it gets on your hands or clothes.
– One of our first products was oil for saw chains on forestry harvesters. Previously, there had been major problems with the oil mist formed when mineral oils sprayed around during sawing. That mist would, among other things, cover the windshield, which then had to be cleaned regularly with solvents. With the new oil, what sprays out simply runs off, and the whole machine is kept clean by it, explains Yijun Shi.
This cleaning effect has become one of the things forest machine owners appreciate most. The same effect is achieved in factories, with cleaner machines and working environments compared with traditional fossil-based lubricants, including bio-oil products. It is also harmless if it gets on the skin, unlike mineral oils, which can cause allergies in some people.
A hydraulic fluid with many advantages
To use the glycerol-based oil in hydraulic systems, it is diluted with water to the desired viscosity.
– The water binds strongly to the oil, which means there is little risk of rust in the system. But to be on the safe side, anti-rust additives are added. Cold is not a problem either; the lubricant remains fluid down to -50 degrees.
For various reasons, however, it has been difficult to get users in the hydraulics industry to try the new oil. One reason is that it is hard to test the new oil in existing systems, since the systems must first be cleaned thoroughly before the new oil can be tested.
– One problem at the beginning was that the solvents we needed to use to clean systems of previous oils were harmful to components in the system. For example, they broke down seals, which led to failures. It has been difficult to prove that it was not the new oil that caused those problems.
In addition, it is difficult to remove all oil; a little always remains in various hidden spaces and can create problems. Even brand-new hydraulic systems contain oil or have been tested with oil before delivery.
A stiff fluid that improves control
They have therefore had to test hydraulic systems assembled from their own components, and they have also carried out tests on other types of systems with good results. The glycerol-based oil is now being tested in real operation in several places, including control systems for hydropower.
– Our belief that the new oil can become the hydraulic fluid of the future is based on the fact that it has so many advantages that suit hydraulic applications. For example, it is not as compressible as a mineral oil. It is a much stiffer fluid, even stiffer than water, which means that hydraulic systems get better control and faster regulation. It also has better cooling properties; we have carried out tests at Danfoss in Denmark and saw that the new oil reduces operating temperature by 10–20 degrees.
Very strong cooling properties
Its cooling properties are also considerably better than those of synthetic ester oils, which are themselves more cooling than mineral oils. The glycerol-based oil has 2–3 times higher thermal conductivity and 10–30 percent higher heat capacity than ester oils.
– Our customers also see the major environmental advantages of a water-soluble oil that is completely harmless in nature. Many companies today invest in green steel and other green components, but the one red component they still have is the oil. With our oil, that too can be turned into a green component. If there is a leak at a hydropower plant, the river is not polluted by oil, and if a hydraulic hose on a tractor breaks and 100 litres of hydraulic fluid leak out, it simply runs down, dissolves in water and causes no damage at all. With mineral oil, proper remediation is required, and even then serious environmental consequences cannot be avoided, explains Yijun Shi.
Hydraulic systems may need to be adapted
Another reason why the hydraulics industry has been reluctant to test the new oil is that hydraulic systems have been designed for fossil-based oils for 150 years. Over time, an interaction has developed between oils and the surfaces of different components, optimizing performance.
– We may need to think differently if we are to start using this entirely environmentally friendly oil in hydraulics, perhaps by modifying component surfaces and so on. We are running a few projects together with component manufacturers, which is very interesting, but we would gladly run more such projects.
As things stand, companies are waiting for demand for the new oil, while component manufacturers are waiting for customer demand.
– It becomes a bit of a Catch-22 situation. In terms of price, the new oil is very competitive. It is significantly cheaper than bio-oils and only slightly above mineral oils. It also performs well in colder weather. Taken together, interest really ought to be greater than it is today, but as all the advantages become better known, the glycerol-based oil has a strong chance of becoming the first choice for hydraulic fluids in the future, concludes Yijun Shi.
