Technical
“Biodegradability is defined as the ability of a substance to be digested or consumed by naturally occurring microorganisms or their enzymes, present in water, air and soil systems”
biodegradable if it biodegrades more than 80% within twenty-one days, (CEC L-33-A- 93), or more than 60% within twenty-eight days (OECD 301). This is the preferred type of fluid, as it will degrade before significant environmental damage has occurred and the affected area will require little in terms of long-term remedial renovation. Vegetable-based hydraulic fluids and some of the synthetic oils are considered readily biodegradable.
based products will typically biodegrade in the environment within two months to two years.
It is important to understand that there are two main types of designations for biodegradability; readily biodegradable and inherently biodegradable. For instant clarification, ‘readily biodegradable’ is the preferred option.
Who can blame a turf manager for getting confused? Purchasing an inherently biodegradable fluid with all good intentions, just to find out that the damage done to the affected area is exactly the same as the original hydraulic fluid he was using?
I apologise for the technicality of the following paragraphs, but it is also important to understand that there are two standards that are primarily used to determine biodegradability - the Coordinating European Council (CEC L-33- A-93) and the Organisation for Economic Cooperation and Development (OECD 301).
According to these tests, a fluid is readily
An inherently biodegradable fluid will degrade very slowly over a longer time; usually months to years. These types of fluids can exist in the environment for several years, continuing to cause substantial damage to turf and subterranean water and require long-term remedial work, due to their environmental persistence. Typically, these products are conventional petroleum-based lubricants.
Right is a table of a few commonly used basestock fluids with their biodegradability, evaluated according to CEC-L-33-A-93, i.e. % biodegraded after twenty-one days:
In future, a new test method for determining biodegradability of lubricants in natural environment (CEC-L-103-12) will be used.
Characteristics and Performance of Biofluids
The physical properties of biodegradable fluids differ from those of hydraulic fluids based on a mineral basestock. Their lubricating properties are superior to mineral basestock fluids as they have good anti-wear properties and a lower pour point.
Fluids made from vegetable oils and vegetable oil based synthetic esters are not water soluble. Their specific gravity, which is
about 0.92 g/ml, makes them lighter than water but heavier than mineral oil products. In contrast to water soluble products, they are retained in the upper layers of the soil following an oil spillage.
Although vegetable based hydraulic fluids are sometimes regarded as having shorter life spans and less temperature resistance, they vary widely. Fluids made from virgin plant oils should be used in machines operating at temperatures between -10 °C and +70 °C, temperature excursions either
Lubricant % biodegraded (Basestock)
Aromatic Esters Bright Stock
Alkylbenzenes Polyols
Polypropylene
Glycols Polyethylene
Glycols
Mineral Oils Hydrocracked
Mineral Oils White Oils
10 - 45 25 - 80
25 - 45
Polyalpha Olefins 20 - 80 Diesters
Vegetable Oils
50 - 100 75 - 100
FEBRUARY/MARCH 2014 PC 131
after 21 days 0 - 95 5 - 15 5 - 25
5 - 100 10 - 30
10 - 70
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