St. Louis study shows B20 buses getting slightly lower mileage
The National Renewable Energy Laboratory (NREL) has just completed the first year of a study comparing St. Louis transit buses running on B20 biodiesel and ultra-low sulfur diesel (ULSD). Surprisingly the B20 buses actually had slightly lower average mileage than the ULSD fleet, 3.52 vs 3.58 mpg. The new study is the first to examine B20 use on buses equipped with exhaust gas recirculation systems. The EGR helps to reduce NOx emissions. Fifteen identical buses were examined in the study with eight of them using B20 and the rest using ULSD. One notable difference is the mileage on the buses at the start of the test. The B20 fleet had an average of 127,000 miles while the ULSD buses had an average of 107,000. With a differance of only 1.6 percent in the fuel efficiency, that difference might be a part of the reason. The study will continue for another year. Reliability and maintenance were comparable for the two groups. The full report is available at the link.
[Source: National Renewable Energy Laboratory]
Reader Comments (Page 1 of 1)
EVan 9:18AM (8/11/2008)
Yea, but B20 is composed of 20% biodiesel made from renewable resources....
B20 wasn't concieved for higher fuel economy, it's intent is to use less diesel.... which it does... 20% less.
So I could see how this article would have a point if B20 buses were using 20% more fuel than ULSD buses but it looks like the difference is pretty small.
In summary: I don't get the point of this article.
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Seth 11:48AM (8/11/2008)
Correct,
So if both buses used within the same amounts of liquid being burned, yet only one was 80% petroleum, doesn't that mean they saved 20% in diesel fuel vs. the non bio bus?
Tagbert 11:05AM (8/12/2008)
Seth wrote "...doesn't that mean they saved 20% in diesel fuel vs. the non bio bus?"
That depends on the amount of petroleum that went into the production of the biodiesel. (not to mention the impact on food prices, forests cleared to plant palm oil, and soil depletion.) Until we have a cleaner source of biodiesel, such as algae, we should be very careful promoting the use of biodiesel.
brn 9:23AM (8/11/2008)
I find it more interesting that there's been an overall decline in mpg since October.
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Phil 10:20AM (8/11/2008)
I hope those buses have lots of people on board.
3.5 mpg is pretty shocking.
At least we shouldn't feel guilty when ecomentalists claim that we should ditch our cars and sweat it out in buses.
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A.J. 10:38AM (8/11/2008)
Don't be too shocked about that bus that only gets 3.5 mpg.
If there are just 10 riders, that's 35 people-miles per gallon.
How many cars driving down the highway have just one person in them? And how many of those get better than 35 mpg?
So the lone ranger in his F-150 is getting 15 people-miles per gallon, but a bus with 30 people on it is getting 105 people-miles per gallon.
Mass transit is generally a much better way to move people.
Brent 4:56PM (8/11/2008)
The buses around here are always empty. Public transportation for a city of 50,000 people is a terrible idea. :)
A.J. 10:23AM (8/11/2008)
"Surprisingly the B20 buses actually had slightly lower average mileage than the ULSD fleet"
This is not too surprising because biodiesel has a slightly lower energy content compared to regular diesel (BTUs). My own experience of running B5, B20 and B100 the - B100 drops off about 5% from the others, B5 and B20 are not really perceptible to me. (but I'm not running any scientific experiments)
Also, @brn, diesels typically get their best mileage when air is dense and colder, so I usually see my best mileage in the fall, at about 50degrees, low humidity (no a/c), etc., and before the switch to winter diesel, which also has a slightly lower energy content.
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Dawn 2:26PM (8/12/2008)
Using biodiesel does help reduce petroleum consumption as well as particulate matter emissions.
The real benefit comes with the use of diesel hybrid buses which are 43% more fuel efficient than CNG buses and 22% more efficient than conventional clean diesel buses! And the good news is that the country's largest transit agencies bought more diesel hybrid transit buses in 2007 than any other type with similar trends expected to continue in 2008 and beyond.
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