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In their article, The Effect of Biodiesel on Engine Lubricants (June issue, page 28), Stephen Marsh and Marco Corradi wrote about some of the potential issues surrounding the use of biodiesel in modern diesel engines. Its a good article and you should read it if you havent already.

They pointed out that while biodiesel has similar combustion properties to normal petroleum diesel, there are significant differences in physical and chemical properties. These differences can impact the fuel injection system as well as the cold-flow properties of the fuel. On the lubricants side, the authors concerns centered on fuel dilution and engine cleanliness issues.

The whole issue of biodiesel got me thinking about the farmers who grow the crops that become biodiesel. The carrot to the farmer is huge here. According to the National Biodiesel Board, an industry trade association, farmers recognize that soy biodiesel is a high-quality product to use in their farm equipment. Even low blends of biodiesel like B2 (2 percent) and B5 (5 percent) offer exceptional lubricity, longer equipment life, lower maintenance costs and less equipment downtime, and a cleaner-burning fuel that is friendlier to the user and the environment. These are some bold claims but are generally supportable.

The group also notes that as far back as 2001, a study completed by the U.S. Department of Agriculture found that an average annual increase in crops to produce 200 million gallons of soy-based biodiesel would boost total crop cash receipts by $5.2 billion cumulatively by 2010, resulting in an average net farm income increase of $300 million per year. Since then the economics have gotten even better.

A recent estimate is that there are about 56 billion gallons of diesel fuel consumed in the United States annually. If that amount were all converted to B2 biodiesel, the amount of soy based biodiesel (B100) required would be 1.1 billion gallons.

The National Biodiesel Board has published the following rationale for biodiesel:

With agricultural commodity prices approaching record lows, and petroleum prices approaching record highs, it is clear that more can be done to utilize domestic surpluses of vegetable oils while enhancing our energy security. Because biodiesel can be manufactured using existing industrial production capacity, and used with conventional equipment, it provides substantial opportunity for immediately addressing our energy security issues.

If the true cost of using foreign oil were imposed on the price of imported fuel, renewable fuels, such as biodiesel, probably would be the most viable option. For instance, in 1996, it was estimated that the military costs of securing foreign oil was $57 billion annually. Foreign tax credits accounted for another estimated $4 billion annually and environmental costs were estimated at $45 per barrel. For every billion dollars spent on foreign oil, America lost 10,000 to 25,000 jobs, said the NBB.

When you look at the numbers and see the impact on farmers, the economy and national priorities, this starts to look like the tsunami from Deep Impact, the asteroid disaster movie from a few years back!

So, what impact might biodiesel blends have on farm engine lubricants and operations? For those of you not too familiar with farm and other off-road operations, the duty cycle (the set of conditions under which a vehicle operates) is quite different from over-the-road trucking. In the table at left Ive tried to identify some of the basics and qualitatively compare the two side by side.

From the very rough list shown, you can see that off-road engines encounter generally more adverse operating conditions than do over-the-road engines.

The most recent upgrade in heavy-duty engine oil classifications was driven by the need to deal with more severe restrictions on emissions. Diesel particulate filters (DPF) have become common on engines introduced beginning in 2007. The API CJ-4 engine oil classification restricts ash content, phosphorus and sulfur to accommodate the use of DPF. However, many of the engine builders who supply the off-road market prefer higher ash, sulfur and phosphorus content in their engine oil formulations to contend with the hotter, more heavily loaded conditions that off-road vehicles face.

When CJ-4 (Proposed Category 10 at the time) was being constructed, the SAPS (sulfated ash, phosphorus and sulfur) limits were hotly debated. Without a great deal of hard data to support it, the limits were finally chosen. Some in the industry are now wondering if the limits were a bit too conservative and arbitrary. It has been reported that some over-the-road operators are sticking with higher SAPS products and simply cleaning particulate traps more often.

In conversations with some of the major off-road engine manufacturers, Ive turned up some interesting observations. Naturally, all are rather conservative in recommending biodiesel fuels. One major off-road engine builder, for example, limits the percentage of biodiesel blends to 5 percent maximum (B5) at this time. In addition, the neat biodiesel itself must conform to ASTM D6751 (in the United States) or EN 14214 (Europe) specifications. The OEMs are most concerned about fuel properties such as low-temperature pumpability, storage stability, and deposit formation in the injection system.

The impact of biodiesel on engine oil is the subject of much discussion. As I mentioned above, off-road engines tend to operate in a much hotter environment and under much more severe loads. Both of these conditions will accelerate oxidation and deposit formation. The introduction of biodiesel-rich blowby introduces compounds that are more prone to forming deposits and oxidation byproducts. In addition, methyl esters of fatty acids (biodiesel is the esterified product of naturally occurring fats) are known to be pretty aggressive towards copper-lead bearings. Early L-38 engine test studies of potential friction modifiers based on methyl esters showed some really scary numbers for bearing weight loss – greater than 1,000 mg! – due to the corrosive nature of methyl esters.

As you can well imagine, the ag market engine builders are very anxious to approve biodiesel at as high a level as possible. Its good business for them and their customers. To that end, they are engaged in some pretty serious engine testing programs on higher biodiesel mixes. While they are all pretty cagy, I have no doubt that there are field tests going on as well.

So lets cut to the chase, as they say. Given the more severe operating conditions found in off-road operations and the potential for more deposit forming tendencies by B100, engine builders are generally limiting biodiesel blends at B5 without major reductions in oil drain intervals. Above that, they are taking a cautious, wait-and-see position. For B100, the recommendation is to cut oil drain intervals in half.

There is concern expressed that the relatively higher fuel dilution resulting from biodiesel blowby will mean a greater chance of low-temperature pumpability problems. Farm equipment may very well be pressed into service at very low temperatures, and there is real concern that the high-boiling, waxy materials from the fuel might restrict oil pick-up and result in oil starvation problems. Low-tem-perature pumpability is now a major concern for biodiesel users.

The same blowby materials might cause deposits to form on hot surfaces during the actual growing season, when ag equipment is used most. Deposits in the ring belt area could result in some real field problems and shortened engine life. Engine oil chemistries meeting the older API CI-4 PLUS category, possibly with added antioxidants, might be called for to control deposit formation.

Biodiesel is a promising avenue to reduce dependence on foreign crude oil imports. It has nearly the same BTU content on a per-gallon basis: B100 is about 8.5 percent lower than No.2 diesel, on average. So B2 or B5 will be undetectable insofar as power is concerned.

With the promise come the caveats: Low-temperature concerns both for fuel and for engine oil; potential deposit debits in the fuel delivery system and the engine itself. The industry has dealt with seemingly insurmountable issues before and tamed them. We can certainly do it again.

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