Biodegradability of Lubricants:
Testing Standards and Environmental Significance


Nowadays more and more industries care about the environment and are increasingly seeking sustainable solutions to reduce their impact on it. Many among them target to earn and maintain ISO 14001 certification, the internationally recognized standard for Environmental Management Systems (EMS) [1].

One aspect under focus in this context is machinery lubrication. Lubricants can potentially pose risks to ecosystems and even people's health when they get into the soil and water. This can happen intentionally through improper disposal methods or accidentally through leaks or spills.


Lubricants differ in their formulation, and consequently, all don't have the same impact on the environment. Understanding the lubricant biodegradability is crucial for making informed choices that balance performance with eco-friendliness.


Lubricant Bio-degradability

A good start to understanding lubricant biodegradability is to note that in the context of eco-friendliness, we do not consider the degradability but the biodegradability.
Biodegradability and degradability are both terms used to describe how substances break down over time, but they differ in their environmental impact and the processes involved.
Lubricant degradability refers to the general ability of a lubricant to break down into smaller and simpler components over time through physical or chemical processes like oxidation or fragmentation, but these processes are not environmentally friendly and don't necessarily mean the resulting components are harmless to the environment.
Lubricant Biodegradability refers to the biological breakdown process of a lubricant. This degradability is specifically environmentally beneficial. Effectively, this process involves living microorganisms such as bacteria, fungi, or other biological agents and the result is the conversion of a lubricant into harmless simpler compounds (Carbon Dioxide, Organic Acids, Water, Hydrocarbons, etc.) depending on the surrounding conditions.
What is required is not just degradability, but specifically biodegradability. This means the lubricant can break down, by natural processes, into harmless substances over time.
Biodegradable lubricants fall in Group V lubricants and are available in various formulations, including Vegetable Oils, PolyAlkylene Glycols (PAGs), and Synthetic Esters. Each of these formulations offers particular benefits according to the application, such as temperature resistance, viscosity, and compatibility with seals, coatings, and materials.


Lubricant Bio-degradability

Several international organizations like ISO, ASTM, OECD, and CEC provide standardized testing methods to assess biodegradability under various environmental conditions. These conditions include aerobic and anaerobic degradation in soil, water, or marine environments, with considerations for specific requirements and regulations. While certain testing methods are applicable to general chemical substances, others are specific to lubricants.


The Organization for Economic Cooperation and Development (OECD)

OECD is an international organization committed to fostering economic prosperity, social progress, environmental sustainability, and overall well-being among its member countries [2].
OECD does not have specific biodegradability testing methods guidelines dedicated exclusively to lubricants. However, several of its test guidelines and protocols are commonly used in the assessment of lubricant biodegradability and environmental impact.


Ready biodegradability refers to the ability of a substance to undergo degradation by the action of microorganisms under aerobic conditions in the environment, resulting in the formation of water, carbon dioxide, and mineral salts.

The OECD provides guidelines for testing ready biodegradability. OECD 301 outlines six methods for screening chemicals in an aerobic aqueous medium, while OECD 310, or the Ready Biodegradability - CO₂ in Sealed Vessels (Headspace Test), offers similar evaluations. Positive results from these tests indicate that a substance is readily biodegradable and can rapidly degrade in the environment [2].

Inherent biodegradability refers to the inherent ability of a substance to undergo degradation by microorganisms under specific environmental conditions, typically without the presence of added nutrients or external stimuli. OECD Test Guidelines dedicated to assessing the inherent biodegradability include:


These OECD test guidelines are all about studying the transformation and mineralization of substances in different environments.

This category of OECD test guidelines focuses on studying the transformation and mineralization of substances in different environments. OECD 307 evaluates the aerobic and anaerobic transformation of chemicals in soil, while OECD 308 assesses the transformation of organic chemicals in aquatic sediment systems. OECD 309 measures aerobic mineralization in surface water. OECD 311 examines the anaerobic biodegradability of organic compounds in digested sludge by measuring gas production. Additionally, OECD 312 studies leaching in soil columns to determine the leaching potential of both the test substance and its transformation products under controlled laboratory conditions.

This category of OECD test guidelines covers methods for evaluating various processes that influence the fate and behavior of substances in the environment:


Coordinating European Council (CEC)

CEC is an organization that represents the motor, oil, petroleum additive, and allied industries in the development of test methods to evaluate the performance of transportation fuels, lubricants, and other fluids [3].

Within the CEC framework, several test methods are available for evaluating the biodegradability of chemicals and materials. These methods are designed to simulate environmental conditions and measure the rate and extent of biodegradation. Among the notable CEC biodegradability testing methods are:


International Organization for Standardization (ISO)

ISO offers a comprehensive framework for evaluating biodegradability.


American Society for Testing and Materials (ASTM)

ASTM has several standards for testing biodegradability, including:


Identifying Lubricant Biodegradability

Confirming a lubricant's biodegradability is easily achievable by contacting the technical support service of the lubricant supplier. Alternatively, there are many other available ways:

Lubricant Technical Data Sheets (TDS) provide comprehensive technical details about lubricants, including environmental data. This might include confirmation statements such as "Readily biodegradable according to OECD 301B" or may be presented within the tests table commonly included in TDS, as demonstrated in the following examples.

However, it's uncommon to find extensive environmental impact details for all lubricants in these documents. Such information is usually provided for biobased lubricants.


Nevertheless, it's mandatory for lubricant Safety Data Sheets (SDS) to include such environmental details.

Environmental Data Standard Value
Biodegradability, % OECD 301 F Readily biodegradable >8
Test Standard Value
Biodegradability CEC L-33-A-93 >90 %

Indeed, Safety Data Sheets (SDS) allocate two out of the 16 sections specifically for ecological information, detailing potential environmental risks associated with a lubricant.

Examples of ecological information extracted from lubricant MSDS:

Eco-certifications from independent organizations like the European Ecolabel and the USDA BioPreferred Program help consumers identify lubricants that meet specific biodegradability criteria, providing assurance of environmental performance.


Conclusion

This informative article aims to draw attention to lubricants in the context of sustainability through exploring their biodegradability testing. Biodegradability is not the sole criterion of sustainability. Biodegradability is one of the three characteristics that are assessed when judging the environmental impact of a hydraulic fluid. The other two characteristics are eco-toxicity and bio-accumulation [4].

Confirming bio-degradability through analysis or identifying it through technical data sheets, MSDS or an eco-label should not encourage improper disposal practices. This signifies just a reduced environmental impact. Implementing proper waste management systems and infrastructure is essential to ensure the complete bio-degradation process occurs.


References

[1] www.iso.com, consulted on May 12th, 2024.

[2] OECD Guidelines for the Testing of Chemicals, Section 3, OECD Publishing, Paris, Environmental fate and behavior, consulted on May 13th, 2024.

[3] www.cectests.org, consulted on May 12th, 2024.

[4] www.astm.org, consulted on May 12th, 2024.


About the Author

Electromechanical Engineer, Certified Machinery Lubrication Engineer (MLE), Machine Lubricant Analyst (MLA Level I, II & III), and Laboratory Lubricant Analyst (LLA Level I) by ICML. He currently serves as a Global Oil Analysis Engineer at APM Terminals within its Reliability Center of Excellence. His main role is to provide technical support in Oil Analysis & Machinery Lubrication across APM Terminals worldwide terminals. He has worked before as a Technical Sales Support Engineer at SGS, where he supported hundreds of companies in Morocco and Africa in the field of Oil Analysis.
Contact Mr. Brahim El Asri at brahim.enim@gmail.com

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