Rail Curve Grease Evaluation -
Biobased Vs. Conventional* Part 4 Biobased Vs. Conventional
Lou Honary, Professor and Director Emeritus University of Northern Iowa
Executive Summary Lubricants and greases that are used in rail equipment can come from biodegradable sources that may be renewable, cost effective and environmentally benign. The intent of this study was to investigate the feasibility of using readily biodegradable rail curve greases in locomotive, rolling stock and other equipment. The University of Northern Iowa, National Ag-Based Lubricant (UNI-NABL) Center performed the research on behalf of the Federal Railroad Administration (FRA), and the activities were divided into three categories: (1) Laboratory Testing, (2) Testing in wayside equipment in temperature controlled environmental chamber, (3) Field testing of lubricants in wayside equipment in a revenue service railroad. The first three articles covered the properties of rail curve greases and the equipment used in dispensing the grease to the wheel flange and track gage face. In this fourth and last part, environmental considerations are highlighted. The complete report is available for free download from the US Department of Transportation web site at:
www.fra.dot.gov/elib/ document/3936.
Environmental Considerations One of the main reasons for using biobased grease for rail road lubrication is the fact that the lubricant is directly discharged into the environment. Curve greases especially present environmental concerns because they are concentrated around the curves where over time they could accumulate on or in the soil. All the test greases in this study were evaluated for their environmental impacts. The tests included test of Biodegradability, test of Toxicity, and test for the amount Biobased Content.
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Biodegradability To test the biodegradability a quantity of grease is dissolved in a sample and along with the reference samples are placed in a controlled environment and then inoculated with standard specified bacteria. The test runs for 28 days and as the bacteria consume food or the biodegradable materials they consume oxygen and release carbon dioxide. After consuming all the nutrients in the sample, the bacteria begin to die out thus oxygen consumption flattens out and then drops. The OECD 301 series tests corresponding to the ASTM tests and basically monitor either oxygen consumption or carbon dioxide evolution. Testing grease in the current biodegradability instruments is difficult because grease does not easily dissolve in water. Due to time limitation the research team selected the reference petroleum grease which was used in all the field tests as well as one bio-based grease that had shown high bio-based content for comparative testing.
The test method used was the OECD 301 test which is a 28 day test. The bio-based grease showed to be biodegradable according to the test method; while the mineral oil-based grease did not meet the percent oxygen consumption as required by the test and thus not considered biodegradable.
For grease, the team spread the required 100 mg weight of grease onto a half a piece of filter paper and placed it into the water and stirred for 24 hours. All the other aspect of the test remained the same and it was run for 28 day at 22 degrees Celsius. The test samples were evaluated against the samples containing sodium benzoate which is the reference food for the bacteria and shows a rapid growth in
the oxygen uptake. The test requires that within the first 10 days of the test, the oxygen uptake by the test sample should reach 60 percent of the reference sample. As expected the mineral based grease did not meet the biodegradability requirement. The testing of the bio-based grease, on the other hand as expected, showed oxygen uptakes in line with the reference samples at the 10th day and throughout the 28 day test. As a result the product can be classified as biodegradable.
Plant Toxicity Test
The test method used for plant toxicity was the OECD 208: Terrestrial Plant Test: Seedling Emergence and Seedling Growth Test. In this test standard seeds are grown in a controlled environment. The emergence and plant shoot are measured and compared. To be considered non-toxic to the test plant, the sample with the product being tested should show growth equal to or greater than 50% of the growth of the reference plant having plant food.
All test greases including the mineral oil based greases passed this test. Therefore, either the results can be accepted as presented or one can conclude that a more sensitive test is needed to differentiate between a product that could impact the plant growth and one that is benign to the plants.
Bio-based Content In the United States, government purchasers are required to give purchase preference to products that meet the Biobased labeling requirements set by the United States Department of Agriculture (SDA). The USDA bio-based labeling requirements include determining the percentage of renewable carbon as an
LUBE MAGAZINE NO.132 APRIL 2016
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