Environmentally Adapted Lubricants, Part 1. An Overview

Mahendra Pal and Sudhir Singhal Petroleum Products Application Divi- sion, Indian Institute o j Petroleum, Dehradun, India

The requirementfor environmentally adapted lubricants has begun to play an increasingly important role in many industrial applications, particularly in the last two decades. The present-day requirements for biodegradable and eco-ji-iendly lubricants imply that lubricants have properties that can minimise, i f not eliminate, negative environmental impact, such as contam- ination o j soil and water, caused by lost lubrication, leakage and accidents. The dominant,factors that have a direct impact on the ensironment and which characterise the lubricant and its chemical composition, are toxicity, bio-ac- cumulation and biodegradability. Biodegradabih'ty is perhaps the most im- portant factor which determines the fate o j lubricant in the environment.

Various commercial, governmental, and regulatory initiatives exist that protect the interests ojthe consumer. Life cycle analysis can help in assessing the total environmental impact of lubricants. This paper reviews the essential requirements of environmentally adapted lubricants, i.e., chemical composi- tion, eco-toxiciv, biodegradability, bio-accumulation, and eco-labelling schemes, and life cycle analysis.

KEYWORDS: environnient, lubricants, biodegradability, life-cycle analysis, bio- accumulation, toxicity

INTRODUCTION

There is an increasing impact on the environment as a result of lubricants en- tering the air, soil, and water. It has been estimated that, worldwide, only fifty per cent of total lubricant consumption is collected, and a considerable amount of the remainder of the fifty per cent comes into direct contact with the envi- ronment due to spillage, machinery failure, leakage throw-off, emissions, and careless disposal.'-' The lubricants lost in this way can endanger the natural environment because of their poor biodegradability and eco-toxic characteris- tics.'.' Most currently used lubricants are based on mineral oils and chemically derived additives, and harm the environment due to their low biodegradability and toxicity.'

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The development of environmentally adapted lubricants is thus necessary to restrict the use of mineral-oil based products in environmentally sensitive areas, such as forests, mines, quarries, railway tracks, agriculture, in water sports equipment, and near drinking water sources.' Renewable and synthetic- based alternative lubricants have been employed to meet the more severe op- erating and performance levels in different applications, with proven benefits and advantages over mineral oils. But these alternatives are often outweighed by technical and economic con~iderations.~

It is a matter of concern for all in the oil industry that our environment has been adversely affected due to our activity, and in particular lubricant manu- facturers. Over the last ten years, a whole new set of requirements related to the environment has been introduced in different parts of the world, by legis- lation, through public concern, and through OEM pressures, to deal with the impact of lubricants on the environment. However, in India, a need has only recently been felt to introduce environmentally adapted lubricants to protect our environment. The aim of this paper is to present some of the environmen- tal issues that relate to lubricants, and to help create awareness of the issues.

This paper describes the nature of environmentally adapted lubricants (EALs) with regards to their requirements, eco-labelling schemes, and the role of regulations and life-cycle analysis.

IMPORTANT REQUIREMENTS OF EALs

Technical and environmental developments continue to increase the perform- ance requirements of lubricants. The new technical and environmental stan- dards present some of the key challenges facing today's lubricant formulators, in terms of selection of base oils and additive systems. Mineral oils, due to their low biodegradability, are not desirable for environmentally adapted lubricants. The technology is developing with which to produce cheaper hydrocarbons suitable as base oils. These differ from conventional mineral oils from both a technical and an ecological point of view. There is, for exam- ple, a growing pressure on lubricant manufacturers to market products that contain recycled oils as an environmental contribution. However, the problem of high polycyclic aromatic hydrocarbons and high chlorine levels in recycled oils makes them unsuitable for producing environmentally adapted lubricants.

The role of the additive in a lubricant is to enhance the properties of the base oil such that the fully formulated product ensures effective lubrication. Although many of the additives used in mineral-oil based lubricants do not

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Eiivironnientally adapted lubricants. Part I . An overview 137

necessarily pose major environmental problems due to their nature and con- centration level in the formulated products, it is still necessary to look into the chemistries of the additives more carefully to ensure that they are appropriate for formulating environmentally adapted lubricants, i.e., in terms of bio- degradability, toxicity, and bio-accumulation. Governmental regulatory initi- atives and ‘eco-mark’ schemes are also necessary for protecting the interests of consumers. Lubricants have traditionally been developed and assessed purely on technical grounds. Environmental requirements have now com- pelled lubricant formulators to consider the fate of the lubricant from ‘cradle to grave’ by life-cycle analysis.

BASE FLUIDS

The greater application of environmentally adapted lubricants can signific- antly reduce the negative environmental impact that has been associated with conventional lubricants. This has become possible by replacing the mineral oils normally used with more eco-friendly base fluids. These new base fluids may be classified as follows: vegetable oils, such as rapeseed oil, soybean oil, and sunflower oil; animal oils, such as tallows; manufactured chemicals, such as synthetic esters (diesters, polyesters, and phosphate esters); or polyglycols, such as polyalkylene glycols, synthetic hydrocarbons (polyalphaolefins, poly- butenes, alkylated benzenes), silicone fluids (poly di-methyl siloxanes, fluoropolymers), and some unconventional HVI mineral o ik7

In terms of techno-economic considerations, the cost of vegetable oils to- day may be two to three times greater than the cost of comparable mineral oils, for the same application, and synthetic esters as much as five to six times cost- lier than mineral oils. Vegetable-oil based environmentally adapted lubricants have been employed in applications such as conventional two-stroke engines, chain-saws, hydraulic systems, metalworking processes, transformers, con- crete-mould release agents, agriculture tractors, and refrigeration systems.’ Ester-based EALs have been used in two-stroke engines, fire-resistant hy- draulic fluids, and metalworking operations, while glycol-based EALs have applications in brake fluid systems, cutting operations, fire-resistant hydraulic systems, gears, compressors, textile fibre processing, rubber processing, and in grease formulation^.^

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Table 1 Water hazard classification

Pal and Sittghal

WEN WGK Classification

0-1.9 0 Not hazardous to water

2-3.9 1 Slightly hazardous

4-5.9 2 Moderately hazardous

>6 3 Highly hazardous

ADDITIVES

Selection of the appropriate additive system is largely dependent on perform- ance specifications, which are driven by OEM requirements. However, en- vironmentally adapted lubricants have also to meet environmentally driven criteria, and additional requirements based on legislative, and health and safe- ty considerations, as well as the market desire for enhanced benefits.x The majority of lubricant additives consist of long-chain organic compounds to ensure solubility in base fluids. These may generally be poor in biodegrad- ability. They possess low aquatic and mammalian toxicity, and are considered not to pose significant environmental hazards.' The main classes of this kind of lubricant additive are succinimides, ashless dispersants, metallic sulpho- nates, phenates, and salicylates as detergents, zinc dialkyldithiophosphates as multifunctional antiwear, antioxidant, and corrosion inhibitors. The toxicity data of some of these additives have been reported?

TOXICITY

Environmentally adapted lubricants should possess both biodegradability and good ecological-toxicological characteristics. They should help in protecting life in atmospheric, aquatic, and terrestrial domains.' Procedures have been developed in recent years to test the toxicity of substances for aquatic organ- isms, such as fish, daphnia magna Straus (a small crustacean), and algae. The best known toxicity classification for impact on aquatic environment is the German W a s s e r g e ~ ~ h ~ ~ u n g k l s s e (WGK) or water endangering class. The class assigned to a substance depends on its WKZ or water endangering num- ber (WEN), which is obtained from measurement of the mammalian fish and bacterial toxicity. The water hazard or water polluting number is determined

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Environmentally adapted lubricants. Part I. An overview 139

Table 2 Test methods for toxicity

Test method Bio-organism or material Parameter

OECD 201/DIN 38412 (IX) Algae

OECD 202/DIN 38412 (11) Daphnia

OECD 202/DIN 38412 (XV) Fish

OECD 203 Fish

EC,, and EC,,

OECD 208 Wheat, cress and rape seed - OECD 209 Sludge

IS0 8192/DIN 38412 (VIII) Bacteria EC,, and EC,,

from the overall WEN, calculated as the average of acute oral mammalian tox- icity (AOMT), acute fish toxicity (AFT), and acute bacterial toxicity (ABT) values.6 The different water hazard classes are defined in Table 1.

Aquatic toxicity levels are based on EC,,, value, which is the concentration of the material which would affect 50% of the aquatic organisms in a test. LD,,, (lethal dose) and LC,,, (lethal concentration) of the material, i.e., which would be lethal to 50% of the test fish or animals during the exposure period, are oth- er important measures of toxicity. Other acute tests include an irritation or sensitisation test, in which the degree to which a substance may cause a reaction after contact with the eyes or the skin is measured.“’ Some of the test methods on toxicity are given in Table 2.

BIODEGRADABILITY

Biodegradation is the process in which a lubricant is attacked micro-biologi- cally by bacteria, yeasts, moulds, and fungi, such as are found in soil or water, to break it down into simpler chemicals that the organism can then digest.6 Al- though the exact biochemical routes of hydrocarbon degradation are not fully known, it is clear that oxygen is important for this process.” The substances have been classified according to their degree of biodegradability, as ‘readily’, ‘inherently’, or ‘relatively’ biodegradable. The test methods for ‘readily’ bio- degradable substances determine the extent of ultimate biodegradation. Materials not succeeding in this test may be termed as ‘inherently’ biodegrad- able, while ‘relative’ biodegradability of lubricants can be measured by the

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Table 3 OECD test methods for biodegradability

(A) Mineral-oil based lubricants

Method No. of days Pass level

CEC-L-33-A-94 21

ASTM-D-5864-95

~70%

>60%

(6) Water-soluble lubricants

Method Country of origin or type of test

OECD 301 A AFNOR, France

OECD301 B

OECD301 C

STURM

MITI, Japan

OECD301 D Closed bottle test

OECD301 E

OECD301 F

OECD 302 A

OECD 302 B

Modified AFNOR

GLEDHIL, USA

SCAS Test

ZAHN-WELLENS EPMA Test

OECD 302 C Modified UK MlTl 11 BOD/COD Test

CEC-L-33-A-94 test developed by the Co-ordinating European Council (CEC)."-12 The Organisation for Economic Co-operation & Development (OECD) and the European Union (EU) have approved these test methods for biodegradability.6 These test have been generally accepted internationally, and have been in use for several years. The test methods are listed in Table 3.

BIO-ACCUMULATION

The bio-accumulation value of environmentally adapted lubricants is an im- portant measure of the constituent substances' accumulation in the fatty tis- sues of animals or fish, and is expressed in terms of the bio-concentration factor (BCF). The BCF is the ratio of concentration of the chemical in the or- ganism to the concentration of the chemical in water. A simple laboratory test for potential bio-accumulation (OECD 107 and OECD 117) reveals the

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Environmentally adapted lubricants, Part I . An overview 141

relative solubility of the substance in water and n-octanol. Water and n-oc- tanol are immiscible, and the substance therefore becomes partitioned be- tween the separate aqueous and organic layers.” A preference for the organic layer is reflected in a high value of the n-octanol/water partition coefficient (Po,). The BCF has been shown to correlate strongly with log Po,. This indi- cates that the bio-accumulation of the substances between Po, values of > 3 and < 6 are generally regarded as having a low or negligible potential to bio- accumulate.13 The bio-accumulation property of a lubricant need not be mea- sured if it is readily bi0degradab1e.I~

ECO-LABELLING SCHEMES AND REGULATORY INITIATIVES

Eco-labelling schemes have already been adopted by a number of countries in Europe and elsewhere as per the directives of their respective governments. These include Germany (Blue Angel), Canada (Environment Choice Pro- gram), Japan (Ecomark), and the Nordic Countries (White Swan). Eco-label- ling is an EU-wide scheme (arising from EEC regulation No. 880/92) which was launched in July 1993, to encourage the manufacturers of consumer pro- ducts to produce items which are less damaging to the environment, and to as- sist consumers in making informed choice^.'^ Products qualifying for an eco- mark are identified by an appropriate logo, and the government is usually en- titled to a licensing fee on the sales values.’s

In India, the Ministry of Environment & Forest, has promulgated an ‘eco- mark’ scheme for lubricating oils based on vegetable and other oil^.'"‘'^ The vegetable-oil based lubricants should have 90% biodegradability, and lubri- cants other than vegetable oil based, 60% biodegradability. The above-men- tioned biodegradability criterion is to be tested as per OECD test method CEC-L-33-A-94 (21 days). The product shall not contain any toxic metals, such as lead or barium. Antimony is not allowed in concentrations beyond 0.25% as tested by AAS methods. The product must not contain halogenated products, such as PCBs, PCTs, and PBTs, or nitrites. The product may contain ~ 5 0 % by volume re-refined/recycled products, which should be reclaimed through an environmentally compatible re-refining process. Any products containing >2000 ppm of halogens and >20 ppm of PCBs are to be treated as hazardous wastes. The product must not have a toxic effect on aquatic organ- isms. EC,,JLC,, shall not be less than I .O mgb.

This promulgation (notified in an official gazette) has some aspects of im- practicality in the way it is stated. The Bureau of Indian Standards (BIS)

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142 Pal and Singhal

therefore set up a task force to prepare a draft on environmental criteria for an eco-mark labelling scheme for lubricants and greases. The object of the scheme is to limit environmental damage by providing information to the con- sumer to enable him or her to select lubricants which are of low risk to have nil effect on the environment by virtue of their superior biodegradability and lesser toxicity, as compared to other products fulfilling the same function. The criteria laid down in this scheme can be adopted on a wholly voluntary basis for these products. This scheme does not in any way address the performance specifications of eco-mark lubricants for their intended applications; however, the product should satisfy normal requirements for intended usage and it should not have significantly poorer properties than normal for the product. The criteria of this scheme are to be subjected to review after three years from its implementation. However, the steering committee is empowered to review the criteria earlier as and when the need arises.

LIFE-CYCLE ANALYSIS

The total environmental impact of environmentally adapted lubricants can be assessed through a complete life-cycle analysis (LCA).',29'0 This includes both base fluid and additives, the use of raw materials, energy, generation of waste, packaging, distribution, product use, and recycling or disposal. The LCA of most lubricants are not yet available. Instead, claims are usually made on a qualitative comparison between an EAL and its mineral oil equivalent.

SUMMARY

Environmentally adapted lubricants are those that can be used in environmen- tally sensitive applications, e.g., in forests, on railway tracks, near drinking water sources. The components of such lubricants, both base fluids and addi- tives, should be assessed for their toxicity, both human and animal/fish, their biodegradability, according to various test methods, and their bio-accumula- tion. The ecological performance of such environmentally acceptable lubri- cants can then be classified with a consumer-aware label. A further step, which has yet to be implemented anywhere on a serious level, is the use of life-cycle analysis, in which the total environmental impact of a lubricant, from inception to ultimate fate ('cradle to grave') is assessed.

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Eiivirortmentally adapted lubricants. Part I . An overview 143

Acknowledgement

The authors wish to thank Dr. T.S.R. Prasada Rao, Director, Indian Institute of Petroleum, Dehradun, for permission to publish this paper.

References

1. Coy, R.C., and Michopoulos, Y., ‘Environmental impact of lubricants’, in Proc. Znterna- tional Tribology Coizftiwzce (ITC-95), Yokohama, Japan, 1995, pp. 845-50.

2. Coy, R.C., Michopoulos, Y., and Wilkinson, J.P.T., ‘Environmental impact of lubricants’, in Proc. 21st Leeds-Lyon Symposium on Tribology, Institute of Tribology, University of Leeds, UK, 6-9 September 1994, published in Lubricants and Lubrication, ed. D. Dow- son, Elsevier Science, 1995, pp. 15-23.

3. Singh, M.P., Chhatwal, V.K., Rawat, B.S., Mistry, M.I.S., Srivastava, S.P., and Bhatna- gar, A.K., ‘Environment friendly base fluids for lubricants’, in Proc. Int. Symp. on Pro- duction and Application of Lube Base Stocks, IIP Dehradun, 23-25 November 1994, pp.

4. Singh, Himmat, ‘Environmentally safe base fluids for lubricants’, Erdole rind Kohlc, 47,

5 . Mang, Theo, ‘Environmentally friendly biodegradable lube base oils - technical and en- vironmental trends in the European market’, in Proc. hit. Symp. on Production and Appli- cation of Lube Base Stocks, op. cit., pp. 66-80.

6. ‘Product review on biodegradable fluids and lubricants’, hid. Lub. & Trib., 48, 2 (1996)

7. ‘Product review on alternative lubricant base fluids’, Znd. Lub. & Trib., 49,2 (1997) 78-88. 8. Biggin, R.J.C., ‘Additives for lubricants with improved environmental compatibility’, in

Proc. Int. Symp. on Production and Application of Lube Base Stocks, op. cit., pp. 55-64. 9. ‘Product review on lubricant additives’, Ind. Lub. & Trib., 49, l(1997) 15-30.

10. Warne, T.M., and Halder, C.A., ‘Toxicity of lubricating oils’, Lub. Eng. , 42,2 (1996) 97. 11. Baggott, Jim, ‘Biodegradable lubricants’, paper presented at Institute of Petroleum, Lon-

don Symposium, ‘Life cycle analysis and eco-assessment in the oil industry’, Nov. 1992. 12. ‘Biodegradability of two-stroke cycle out-board oils in water’, Co-ordinating European

Council for the Development of Performance Tests for Engine Lubricants and Fuels, Ten- tative Test Method CEC-L-33-T-82 (1982), now approved CEC-L-33-A-94 ( 1994).

13. Hushan, J.M., et al., ‘Use of OECD premarket data in environmental exposure analysis for new chemicals’, Chemisphere, 12, 6 (1983) 887.

14. From a summary of considerations in a report from an OECD expert group on degradation and accumulation, OECD Guidelines for Testing of Chemicals, OECD, 1992.

15. Technical bulletins from BLF, Ind. Lub. & Trib., 48,6 (1996) 3 1-4. 16. ‘Draft criteria Tor labelling lubricating oils as environmental friendly products’, Ministry

of Environment & Forest, Government of India, in The Gazette ofIndia, Extraordinary Part 11, Section 3. Subsec. (i) No. 269, dated 18 June 1992, vide GSR 599 (E).

17. ‘Draft criteria for labelling lubricating oils as environment friendly products’, Ministry of Environment & Forest, Government of India, in The Gaiette of India, Extraordinary Part 11, Section 3. Subsec. (i) No. 364, dated 7 September 1995, vide GSR 620 (E).

362-72.

2 ( 1994) 68-70.

17-26.

This paper was first presented at the 1st International Conference on Industrial Tribology, Calcutta, India.

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