Using Biodegradable Lubricants in Farm Equipment

J.M. Perez; G.C. Caufmann ; L. Holland, Pennsylvania State University

With 3,000 acres of farmland and 200 pieces of farm equipment, Penn State University’s College of Agriculture has an ideal situation for researching new technology of interest to farmers. However, fluid spills due to line breaks often occur here and must be cleaned up using a strict protocol enforced by the Penn State Environmental, Health and Safety Department (EHS) and the state’s Department of Environmental Protection (DEP). Over the years, numerous hydraulic fluid spills have resulted in clean-up costs ranging from a few thousand dollars to $20,000. This was incentive to convert to more expensive biodegradable hydraulic fluids.

Conversion to biodegradable fuels and lubricants has been an ongoing effort at Penn State since 2003. All farm equipment hydraulic fluids were changed out to biodegradable fluid. Biodiesel fuel studies resulted in conversion of all diesel farm equipment to B20, and currently some tractors are using B100.

A field test was initiated, and periodic samples were randomly taken and analyzed. The study included both small and large farm equipment. Samples were analyzed for metals, acid number, water and contaminants. In addition, laboratory friction and wear tests as well as infrared analyses were conducted. Crankcase samples were also taken on some tractors operating on B100 to investigate the effect of blow-by contamination on the lubricant.   

Test Methods

Random samples were taken periodically, and the following analyses were conducted.

Metals — Samples were analyzed by inductively coupled plasma (ICP). In addition to total metal content, copper, iron, lead, silicon and some additive components such as zinc and molybdenum were analyzed.

Acid Number — Acid number was determined using ASTM Method D974.

Contaminants —ISO particle counts were included.

Viscosity — Viscosity measurements at 40 degrees C were conducted using ASTM Test Method D445.

Infrared — Fourier transform infrared (FTIR) analyses were conducted using a Nicolet AVATAR 360 Spectrometer IR and the OMNIC ESP 5.0 software to determine if changes in functional groups of the samples occurred with use. Improper oil additions could also be detected.

Friction and Wear — Tests were conducted using the four-ball wear tester (Figure 1). Test conditions included 0.5-inch-diameter stainless-steel ball bearings, 40 kg load, 600 rpm, 60-minute test time and 75 degrees C or 100 degrees C test temperatures. Friction data was recorded every 30 seconds and averaged.

                                           Figure 1. Four-Ball Wear Test


Test Fluid — Several commercial fluids were evaluated and compared to the equipment manufacturers’ recommendations. In addition, approval by the DEP was required to meet spill requirements pertaining to ground water contamination. The properties of the vegetable oil-based hydraulic fluid are found in Table 1.

The Results

To date, no problems have been encountered with performance or maintenance of the equipment. Operator acceptance also was good as a result of significant reductions in emissions.


The FTIR spectra comparison of a new and used sample of biodegradable hydraulic fluid is shown in Figure 2. The fingerprint for vegetable oils is in the range below the 2000 wavenumber. The sample shown was in use for more than two years. The absorption CH, C=O and C-O bands remain essentially unchanged.

Figure 2. Infrared spectra of new and used hydraulic fluid samples

Metal Content

A comparison of the total metal content of petroleum samples taken at the time of changeover and the data accumulate on the field test is shown on Figure 3.

The metal content of some of the initial samples from the biodegradable hydraulic system was high due to cleaning out the system. Lead and copper content of the samples remained low over the four-year test period.

Viscosity and Acid Number

No significant change in acid number or viscosity occurred during the field test.

Friction and Wear

Typical results obtained from the four-ball wear tests are found in Table 2. Test results of used samples were from various units. To date, no unusual maintenance problems have been noted with any of the equipment using the biodegradable fluids.

B100 Blow-by

Four tractors operating on B100 were placed into the field test in 2007. Periodic sampling of the engine oils revealed no significant blow-by effects on the crankcase lubricant. To date, the level of biodiesel found in the engine oil by differential FTIR and changes in viscosity measurements have been less than 5 percent. This may be due to the newness of the engines and the type of emission system. There is no late injection timing to light off catalysts in the system.

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