Biolubricants How to choose the most appropriate ultimate biodegradability test method?
Vincent BOUILLON
BFB OIL RESEARCH S.A. ; Les Isnes (Gembloux); BELGIUM
vincent.bouillon@
bfblab.com
1. Introduction
The use of bio-based materials is beneficial with reference to the fossil resources depletion, the climate change and the water and soil pollution. In some application the lubricant is directly widespread in the nature due to its normal use like in the loss lubrication ; in some other applications, leakages or accidents leads to contaminate the environment.
Moreover, it is recognised in the CEN 16227 that, in Europe, more than 1 million ton per year is not recovered and more than 7 millions tons of lubricants remains every year in the environment.
The biodegradability of a product is a key parameter which is needed for many diretives like REACH, GHS but also for the Vessel General Permit (VGP) in marine applications, the European Ecolabel as well as many National ecologic label (Blue Angel, White Swan,…). This is also a major property in the evaluation of LCA, an exposure scenario or to fill in the data in a MSDS or technical sheet for transport, waste management,… so its evaluation has to be done with the most appropriate test method. In this paper, only the aerobic biodegradation will be reviewed.
2. Overview of the ultimate biodegradability test methods
2.1. Primary and Ultimate biodegration
Many terms are used to define a test substance as biodegradable – primary, potentially, fully, readily, ultimate,… The first important difference that must be done is between the primary and ultimate as well as readily or inherently biodegradation:
The primary biodegradation is the alteration in the chemical structure of a substance, brought about by biological action, resulting in the loss of a specific property of that substance. The laboratory tests which are carried out to evaluate this primary biodegradation are mainly based on a determination
of the residual test substance content after a incubation period. In the eighties, the test CEC L-33 approved in 1993 (obsolete now) based on residual oil content determined by IR spectrophotometry after solvent extraction at the end of 21 days incubation period has been developped. This test was first dedicated to 2-strokes outboard engine oils. The french method NF T 60-198, based on the same principle, extended the scope to many types of lubricants like the hydraulic fluids. More recently, the primary biodegradability test CEC L-103 evaluates the residual oil content by chromatography.
Even if these tests give a good indication fort he potential of biodegradation, they are based on the lost of parent substance rather than mineralisation. Moreover, it can lead to erroneous high value as it becomes difficult to extract completely short polar hydrocarbon chains.
The ultimate biodegradation (aerobic) is the level of degradation achieved when the test compound is totally utilised by micro- organisms resulting in the production of carbon dioxide, nitrate, sulfate, mineral salts, water and new microbial cellular constituents (biomass).
A chemical is defined as readily biodegradable if this chemical has passed certain specified screening tests for ultimate biodegradability; these tests are so stringent that, according to OECD guidelines, it is assumed that compounds which reach the pass level will completely biodegrade in aquatic environments under aerobic conditions. The test methods usually used are the OECD 301 A/B/C/D/E/F and OECD 310 guideline and their equivalent methods.
Inherent biodegradability tests possess a high capacity for degradation to take place. These test procedures allow prolonged exposure of the test substance to microorganisms and a low test substance to biomass ratio, which makes the tests powerful. Some of these tests may be conducted using microorganisms that have previously been exposed to the test substance, which frequently results in adaptation leading to a significantly more extensive degradation of the chemical.
A substance yielding a positive result in a test of this type may be classified as inherently biodegradable, which, preferably, should be qualified by one of the terms “with pre-adaptation” or “without pre-adaptation” as appropriate.
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LUBE MAGAZINE NO.126 APRIL 2015
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