Addressing The Myths Around Biodegradable Lubricants
Environmental issues feature highly on everybody’s agenda and organisations across the world have become increasingly interested in the ‘green’ lubricants available on the market. Becoming essential in applications where there is possible direct contact with the environment, demand for ‘green’ lubricants is growing for machinery operating in sectors such as forestry, agriculture, mining, construction, railways, earth moving, marine and water treatment.
However, what actually constitutes a ‘green’ or ‘environmental’ lubricant? Are they actually kinder to the environment? In the majority of cases, ‘green’ claims usually include an element of biodegradability. “As part of their commitment to sustainable development, Shell lubricants companies have developed and promote the use of lubricants designed to have reduced impact on the environment. Proven to be successful in performance qualities, these Environmentally Considerate Lubricants (ECLs) address both biodegradability and eco-toxicity” explained Frederic Farshchi, Shell Industrial Lubricant Global Marketing Manager.
If a lubricant is referred to as ‘biodegradable’ it would be reasonable to conclude that this means it would be removed quickly and naturally from the environment in the event of a leak or spill. Although minimum levels of biodegrad- ability exist in most ‘eco-lubricants’, the differences in the test conditions and how biodegradation is measured make it difficult to be certain of the environmental credentials of a lubricant.
A degree of confusion can be caused by the terms used in defining biodegradation, and it is worth clarifying these. Biodegradability is the ability of a lubricant to be broken down by micro-organisms, such as bacteria and fungi, to simpler
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compounds. The first stage is the loss of parent material, or ‘primary’ biodegradation. This is the alteration in the chemical structure of a substance, brought about by biological action, resulting in the loss of its specific properties. This does not mean that complete biodegradation has occurred, as the substance might still be present in different chemical forms. Ultimate or aerobic, biodegradation is the level achieved when the test compound is totally utilised by micro-organisms, resulting in the production of carbon dioxide, water, mineral salts and new microbial cellular constituents (biomass).
A substance which is ‘readily’ biodegradable has passed certain specified screening tests for ultimate biodegradability. These tests are so stringent that it is assumed that such compounds will rapidly and completely biodegrade in aquatic environments under aerobic conditions. This level of biodegradability is the highest level achievable, and as such the ultimate aim for lubricant manufacturers.
If results
from an appropriate test show that more than 60% of the product has biodegraded over a 28 day period, then it is defined as ‘readily’ biodegradable’. However, ‘readily’ biodegradable is often confused with another level, defined as ‘inherently’ biodegradable. Although this is a classifi- cation of chemicals for which there is unequivocal evidence of biodegradation (primary or ultimate) there is no indication of how quick or comprehensive the
process is. Therefore products claiming to be inherently biodegradable might not be as environmentally friendly as the customer is led to believe. “The appropriate test result for ‘inherently’ biodegradable is that between 20 and 59% has biodegraded in the 28 day period, or 60% or more over a longer period” explained Frederic.
With a variety of test methods available, it is essential to
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