Biodegradable lubrication oils may have been around for years, but due to changes in environmental legislation, a more responsible stance on sustainability and current market conditions, interest has grown in these products. In this article, we’ll define what a biodegradable oil is and how it differs from other more conventional lubrication types. Read on to find out more.
Types of biodegradable lubricants
Biodegradable lubricants come in many forms like fluids and grease, but they are also divided into different categories.
Readily biodegradable lubricants
These lubricants are environmentally acceptable products that rapidly decompose via microorganisms. To be classed as readily biodegradable, lubricants must have low toxicity for aquatic organisms and achieve a minimum of 60 per cent biodegradation in 28 days. This excludes most oils with a mineral base.
Readily biodegradable lubricants are non-bioaccumulating products. This means they don’t contain zinc and other heavy metals. Bioaccumulating materials don’t pass through organisms as waste, but accumulate within them.
Inherently biodegradable lubricants
This category is comprised of environmentally acceptable lubricants (EALs). Like readily biodegradable lubricants, they degrade naturally to become harmless elements through microbial action, but at a much slower rate. Inherently biodegradable lubricants
are characterised by a biodegradability rate of over 20 per cent in 28 days. They are typically engineered with base oils and additive packages that are non-bioaccumulating and less toxic. Most mineral oil-based lubricants manage to meet this requirement.
Synthetic esters and vegetable oils
Vegetable oils are triglycerides that occur naturally from plants that microbes readily consume. Examples include sunflower and rapeseed oil. In contrast, synthetic esters are man-made. These lubricants are formulated to break down rapidly via microorganisms. However, both types of lubricants are employed in environmentally sensitive applications while having very different molecular structures. In terms of performance, biodegradable synthetic esters are often superior to vegetable oils, particularly when operating at higher temperatures.
Common applications of biodegradable lubricants
Many applications benefit from biodegradable lubricants developed by brands like Valvoline and Houghton, among others. In forestry and horticulture, they see use in machinery at work in green spaces like harvesters, pickers and chainsaws to avoid harming plant life and contamination of soil and watercourses. They also power hydraulics, serving excavators and tunnel borers working near environmentally sensitive sites.
Biodegradable lubricants are employed in various water applications when environmental protection is a prioritised. Usage is often mandatory to meet regulations in areas like offshore environments and waterways.
They are also critical for “total loss” systems that see lubricants released during operation. If a spill or leak occurs, biodegradable lubricants break down naturally, reducing pollution.
Understanding the difference between ‘inherently biodegradable’ and ‘readily biodegradable’
Many available lubricants, like traditional mineral oils, will eventually break down over an extended period because of their natural properties. These lubricants are described as being ‘inherently biodegradable’. However, there are other lubricants that are specifically produced to degrade at a far faster rate, and these are referred to as ‘readily biodegradable’.
Industry standards have been established to measure biodegradability in lubrication products. For instance, OECD 301B and ISO 9439 state that for a lubricant to be categorised as readily biodegradable, it must be capable of degrading by over 60 percent within a 28-day period. The built-for-purpose test requires a lubricant sample to be treated with microorganisms where oxygen is present. Lab technicians then measure how much CO2 is produced by microorganisms in the lubricant.
When must a biodegradable lubricant be used?
Several applications require or recommend the use of biodegradable lubricants – for example, when an application involves a specific risk of the environment being exposed to an oil leak, or when environmental legislation or regulations requires their use.
In marine and offshore gas and oil sectors, where vessels and equipment in a marine environment have the potential to leak oil, there is now a growing global trend for biodegradable lubricants to be used in such applications.
Biodegradable lubricants are also a suitable option for farming operations. Stationary and mobile agricultural machinery and vehicles can leak oils while operating, and fluids can seep into the soil and enter underground water courses. Selecting a biodegradable lubricant can mitigate potential pollution and harm to land and animals, which both represent a significant investment to the farming enterprise.
How do biodegradable lubricants compare with traditional oils?
Historically, biodegradable lubricants have been unable to deliver the performance benefits that are equal to conventional lubricants; however, technology is always advancing in this field.
When engineering a biodegradable product, different base oils can be selected. Polyalkylene glycols (PAGs), vegetable oils and esters are all examples. While all are readily biodegradable, they do not deliver the same performance levels. For top performance, experts recommend biodegradable lubricants that use synthetic esters.
