Bio-based materials for lubricants
In recent years there has been a drive to promote bio- based materials as replacements for products based on fossil carbon. For the bio-producers, lubricants are an attractive market, both because of the large volume and because of the close links between lubricants and the fuels sector, where bio-fuels are now well established.
The initial push for bio-based lubricants focussed on promoting wider use of vegetable oils as basefluids. The main result was the rediscovery of their performance limitations in mainstream lubricant applications, although there have been significant increases in usage in some sectors, particularly hydraulic and transformer oils. Subsequent developments have been more directed towards products which represent a lot more upstream chemical or biochemical processing.
One proposed approach is to develop ‘bio-refineries’ which would use agricultural or municipal waste streams as raw materials for production of the same basic chemical building blocks that we currently make from petroleum. This would allow production of bio-based versions of current synthetic and GTL fluids. If these could be manufactured at competitive cost, they would obviously be drop-in replacements in existing applications.
Annual Carbon Usage
An alternative approach is to use novel processes to make new bio-materials which are not accessible from fossil sources. Current examples being offered into lubricants include bio-based ‘mineral oil lookalikes’ based on estolides, isoprenoids and olefin metathesis products.
As with any new product development, there are two basic questions to answer. The first is “can we do it?” In particular, one concern that is often expressed in relation to bio-based materials is whether there is actually enough biomass around to serve an industry as large as lubricants. Figure 1 compares annual usages of fossil and bio-based carbon. (The relative quantities are given into terms of their energy content to correct for the different chemical compositions). It is apparent that although lubricant basefluids represent a significant fraction of total petrochemical materials, the overall quantity is small compared to total bio-based carbon. Obviously, using crop residue as raw material is not easy. It is widely dispersed, mostly in intractable chemical forms like cellulose and lignin, and much of it is already used locally as low grade fuel or fodder. But there would certainly be no shortage of bio- based carbon for an economically attractive application.
Figure 1. Global usage of fossil and bio-based carbon by application.
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LUBE MAGAZINE NO.128 AUGUST 2015
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