20. U.S. Biodiesel Production National Biodiesel Board Production Potential for 1 Billion Gallons RFS-2 Changes to EPACT Bioenergy Program Biodiesel Tax Incentive
Here you see the chart on lubricity. The diesel equipment companies recommend that the lubricity using this HFRR (high frequency recriprocating rig) test should be below 450. So the wear scar when this test is run should be a low wear scar, which is a good thing. The actual ASTM spec for that, which was recently set, is actually at 520. This chart shows that, as you add more biodiesel, you significantly increase the lubricity from a value of 575 to below 400 with a little less than 1% biodiesel. An interesting phenomenon is that if you add more biodiesel, you don’t get any additional lubricity benefits. So biodiesel has the property whereby just adding small amounts of biodiesel can provide the lubricity you need. In this case, 2% biodiesel had 66% more lubricity than the No. 2 fuel. This No. 2 fuel would be out of spec with today’s diesel fuel spec. So even in low concentrations, biodiesel can bring back the lubricity of fuel. One of the great attributes of biodiesel is it’s a fuel, so if you add more biodiesel, you’re not concerned about overdosing issues, whereas if you use a lubricity additive there is the possibility of overdosing and causing injector coking to happen. You could potentially create a problem by solving a different one. But with biodiesel, that is not an issue. You won’t get any more lubricity benefit, but you won’t have any overdosing issues either. So biodiesel has some significant physical and chemical property benefits compared to conventional diesel fuel, so that is one reason why people are interested in biodiesel.
To summarize, biodiesel and biodiesel blends are compatible with diesel particulate filters—and biodiesel provides some distinct advantages compared to petrodiesel alone (read bullets directly). There is one feature which is in the process of being investigated with some of the new particulate trap engine that technicians should be aware of. That feature is how the raw fuel is injected into the system to provide the fuel needed to burn the particles off the PM trap. There are two means to do this. The first way, which is used on most of the new PM trap equipped medium and heavy duty machinery in the US, is through a small fuel nozzle in the exhaust stream right before the particulate trap. Biodiesel blends—including pure biodiesel—work well with these systems. The second way is to use the injectors in the engine to vaporize raw fuel after combustion and during the exhaust stroke. This is called in-cylinder post combustion injection. Injection in this mode saves a fuel nozzle, but it creates more of an opportunity for fuel to hit the cylinder walls and get washed into the engine oil sump by the piston rings. This happens with petrodiesel alone, and the presence of biodiesel may make it a bit worse. Cummins did not identify this as an issue with B20 in the 1000 hour durability run on the prototype engine, and Ford doesn’t see this as an issues with their new engine, but some light duty car makers say blends over B5 are not recommended because of it. The jury is still out on this particular issue, but if it does happen you will see the level of oil on the dipstick actually go higher over time and if it goes too high that could cause the sump to fill up and cause problems or lower the lubricating properties of the oil. This phenomenon may require more frequent oil changes for B20 blends, or watching the oil level more closely with those models that use in-cylinder post injection but at present it only appears to be newest foreign light duty models that are affected.
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