The Slippery Slope of Biolubricants and Biogreases

By Raj Shah and Shana Braff | August 29, 2018

The lubricants industry is acutely aware of the need for environmentally conscious options and sustainable development choices. In response to demand, biolubricants and biogreases began to make their mark a few years back. The term biolubricants applies to all lubricants that biodegrade expediently, and are nontoxic for both human beings and aquatic habitats. They may be plant-oil based, or synthetic esters manufactured from modified renewable oils. Furthermore, in keeping with the public demand for utilizing renewable resources and increasing concern for products that protect or reduce the amount of harm to the environment, lubricant suppliers have begun seriously employing the use of a diverse panoply of bioproducts. Included in this trend are biogreases that degrade into simple substances not detrimental to the environment, and in some cases, are even based on renewable raw materials. These lubricating greases are especially tailored to applications where there is a great possibility of product seeping into the natural environment. Although biogreases have been in existence for a long while, they have been unable to fully realize their potential and proper place in the grease market.

Presently, the rising costs of crude oil, the depletion of crude oil reserves globally, and worldwide concern for environmental preservation have all contributed to reinvigorated interest in developing and employing environmentally friendly lubricants derived from alternative sources.

Biogrease is also known as an environmentally acceptable lubricant (EAL). This apt terminology denotes lubricants that have successfully achieved standards set for biodegradability, toxicity and bioaccumulation potential. They are likely to have little or no impact on the aquatic environment compared to conventional lubricants, whereas lubricants that are hypothesized to have positive environmental properties—but have yet to be proven to meet these high standards—are known as environmentally friendly lubricants (EFL).This is a bit of a misnomer, since they are not actually environmentally friendly, but are hypothesized to pose a minimal impact on the natural environment.
Biogreases are particularly well-suited for lubrication of forestry machinery, construction vehicles, rail curve, rail flange and marine applications. In all the aforementioned examples, there exists a clear loss-lubrication situation where the lubricating grease eventually ends up in either soil or water. Currently, the market contains several high-performance biogreases, but produced volume remains scanty.

Some issues impeding the pathway to biogrease’s mainstream viability pertain to its performance level—perhaps not always sufficiently justifying the cost incurred, as well as the fact that current legislation does not favor the use of these alternative lubricants.

The efficacy of biogreases is usually highly reliant on the specific base fluid utilized, and the consensus of biolubricants has been that they are low-performing products, which isn’t always the case, and is usually only a major factor where vegetable oils are employed. This was typically what biolubricants were based on in the past. These products often had inferior performance in comparison to equivalent mineral oil-based greases. Another problem was that they were prone to age hardening. The comparison is not a perfect one though, since the main factor at that time was biodegradability as opposed to top performance, under vast temperature span. It still maintains a valid place in this niche market segment, however.

Today, most modern biogreases are formulated with different biodegradable synthetic esters that are expensive, and since the majority of a grease formulation consists of oil, the ester is a major contributor to the product’s cost. Customers are often reluctant to pay such a premium solely to have a biodegradable product in their range. More price-competitive vegetable oil-based products are available, but incapable of delivering sufficient in-service performance levels required by certain market demographics that would otherwise be benefited by the use of a biodegradable grease.

In the event of consumption volumes increasing, lubricating grease manufacturers would be able to produce biogreases more economically. As it stands now, the biogrease market is stuck in a stalemate situation that needs to be ameliorated if it were to gain any true traction as a viable alternative.

Biolubricants are derived from vegetable and plant oils, a variety of nonfood biomass energy. Our planet is highly dependent on the use and consumption of fossil fuels to fulfil its energy needs. However, our petroleum-based economy may not be sustainable indefinitely. Therefore, alternatives need to be explored beyond merely inexpensive, nonrenewable, fossil-based oils and materials to meet our energy requirements. Biolubricants is the term used mainly to refer to liquid oils derived from renewable or biomass feedstocks. They are formed by heating biomass in the absence of oxygen, called pyrolysis, or partially combusted in a limited oxygen supply to produce an oil-like liquid. This bio-crude oil is further refined into various other biolubricant and bio-oil-based products.

It must be noted that there are some technical difficulties that are associated with this conversion process, as the acidic value and water content of the resulting biocrude oil is high, plus energy (possibly fossil fuel energy) has to be consumed in its production. This is in stark contrast to plant and vegetable oils, which are composed primarily of different natural oils, fats and acids, making them biodegradable and nontoxic. These natural oils sometimes have good lubricity without the need for additional additives, and come in a range of viscosities. However, the properties of some kinds of vegetable oils, such as low melting points and oxidative stability, can limit their use as a biolubricant.

Alternatives to petrol, diesel and other types of fossil fuels have already been put into effect in a number of biomass-based transportation fuels such as biodiesel and bioethanol. Biofuels obtained from sugar cane and oil crops for transportation, unimaginable a few decades ago, are now becoming a bit more quotidian, thanks to advanced biofuel pumps being installed in filling stations in certain areas. Consequently, it could be viewed as a natural progression that, as well as filling our vehicles with biofuels, we should also fill them up with biolubricants.

The replacement of fossil fuels and mineral oils with newer, biodegradable lubricant-based oil can aid in substantially diminishing environmental impact and pollution. Vegetable oils have a large number of other innate positive attributes that imbue them with an advantage over conventional petroleum oils as the feedstock for biolubricants. Some of the qualities of vegetable oils, such as excellent biodegradability and low ecotoxicity, are of particular importance for oils and lubricants used in environmentally sensitive areas.

Despite the many advantages of plant-based oil products for biolubricant production, there are challenges for consideration. These include operating temperature limitations, low flash point and potential fire hazards, quick aging and degradation of bio-oils, lack of viscosity range, poor low-temperature fluidity during winter months, compatibility with existing oil seat and gasket materials, and easy formation of sludge resulting in filter clogging and increased maintenance.

Today, market demands and development for biolubricants and transportation fuels have increased environmental compatibility, reduced harmful emissions, improved performance (including longer lifespan and energy efficiency), and most notably, has decreased our dependence on fossil fuel energy. This reinvigorated zeal for vegetable oil as biobased lubricant has increased exponentially as environmental awareness has grown and become a mainstream concern. Emphasis on development of renewable, biodegradable and environmentally safe industrial fluids such as biolubricants has led to the expanding use of natural fats and oils for nonedible, industrial purposes.

It should be noted that transition to biobased, high-performance lubricants requires keen insight into the interdependence between physiochemical and tribological properties of the biobased ingredients. Transitioning from a tried and tested mineral oil to an environmentally acceptable lubricant or EAL will substantially impact the mechanisms relying on the oil performance of journal bearings, transmission gears, thrust bearings, ball bearings, cam followers and, perhaps most dramatically, rubber-based sealing components. These mechanisms are optimized for its use under mineral oils, therefore new design protocols may be necessary when running together with EALs. This means it is crucial to consider the consequences of using these new ecofriendly lubricants on the entire tribosystem before replacing more traditional mineral oil.

While there are sure to be some growing pains, the current drive toward conservation is sure to continue to propel renewed fervor in the use of modified natural oils for nonedible automotive and industrial purposes. The past few decades have resulted in exciting progress in the use of reliable biodegradable lubes and greases from a variety of renewable sources that promises to keep the world flowing toward a more ecologically sound tomorrow.

Authors: Raj Shah
Director, Koehler Instrument Company

Shana Braff                                                                                                                     Customer Service Representative, Koehler Instrument Company