There has been a lot of mention nationally about the use of biodiesel fuel, some of it seeming accurate at times and some of it appearing to be hopelessly optimistic.

Have there been any REAL studies of the use of biodiesel as a fuel for steam locomotives? By this I mean not only the viability of burning it, but also some accurate estimates of the stack emissions, and the total pollution produced versus using the same fuel in a diesel to do the same work.

For example: For identical power output what is the actual fuel consumption comparison between a “best case” steam application and doing the equivalent job with a modern diesel? Is it in fact the comparative ratio of overall thermal efficiency of the two machines?

If that is the case, is the fuel consumption (and expense) of burning biodiesel in a steam locomotive going to be roughly 5X a diesel doing the same work (the ratio between 7% and 35% typical thermal efficiencies)?

If Biodiesel has a lower heating value per unit weight than heavy oil fuels, how much more Biodiesel fuel would be consumed by a steam locomotive to do the same work as it would on heavy fuel, and would the additional expenditure of energy and resources to transport the greater amount of Biodiesel negate any environmental benefits of the fuel?

I am asking this because it is possible that sooner or later somebody will run into a reporter in the news media who does a little bit of research and asks these questions too.

Used fryer oil(filtered for particulate matter) is being used quite successfully at Disney World. Not actually bio diesel...more like unprocessed bio diesel. Their fuel consumption has dropped by 20 to 30 percent depending upon the locomotive. What is essentially used corn, peanut and canola oil burns VERY clean and a bit hotter.
One could hypothesise that pure corn oil would do quite well.

I could go into further detail off line for anyone that is interested.

I have also heard that Disneyland here in California has converted their steam fleet to biodiesel (though lots of people confuse vegetable oil with biodiesel).

Sadly, I have not seen any definitive studies along the lines of your questions but I can add a few thoughts to the discussion. The reason that the Disney World engines are burning hotter is that vegetable oil and bio diesel have a higher cetane rating than standard diesel fuel. This turns out to be advantageous in a steam locomotive as it leads to the observed hotter fire and better radiant heat transfer (the dominant heat transfer mode in an oil burner if memory serves). This probably accounts for the improvement in fuel economy for the Disney World locomotives despite the lower BTU value of the fuel.

The hotter fire would lead to higher NOx emissions. This is something currently being discussed in regard to the use of biodiesel in cars - particulates, CO, CO2 are lower, but NOx is higher.

We have tried a 4% mixture of biodiesel in with our regular burner fuel on the 3751 without any problems. Anyone considering a conversion needs to know that biodiesel, although biodegradable, is a more aggressive solvent than regular diesel fuel - this could loosen up old sludge in a fuel tank and lead to a plugged burner. This is one of the reasons we went with such a weak mixture during our recent experiment with the 3751 - better to either completely cleanout the tank or slowly introduce biodiesel so as not to loosen up a bunch of old heavies in the tank.

For more information on biodiesel, you could look up the website for the National Biodiesel Board.

Jason - Please contact me offline as I would be interested in more information on the Disney World vegetable oil use.

Thanks,

I would like to hear more about this as well. It is my understanding that all of the fry oils mentioned thus far, have less BTU than diesel #2, as does BIOdiesel, but perhaps there is some piece I have missed. Wolf, I don't see how the Cetane would carry more heat, except that it might take less energy to ignite the fuel, and therefor carry over more heat to the firebox. This study/sight has some interesting numbers on the fuels, mixes, and BTUs: http://www.ag.ndsu.edu/pubs/ageng/machine/ae1240w.htm

Sully

I once heard Cotton Belt 819 was burning corn/vegetable oil when it was revived in the 1980s. Is that true?

You can have all the BTUs you want in a fuel, but if you are not burning it effectively and maximizing your dominant mode of heat transfer, the BTUs are wasted. Herein lies the difference between theoretical comparisons and actual practice.

The higher cetane rating means the fuel burns faster, so more of it is consumed while still in the firebox and less is wasted as soot. The resulting hotter fire is also brighter, which improves radiation heat transfer (increases with a 4th power of temperature). This also gets into the higher NOx formation, which also increases with combustion temperature.

All this is moot if the locomotive cannot breath properly. In my diesel car, I get an every so slight decrease in MPGs on biodiesel...but that is not necessarily a direct comparison as the diesel engine is an internal combustion engine that is usually air starved vs. a steam locomotive that with a proper air openings in the firepan, draft system, etc. should have plenty of air for its external combustion process.

I am a bit rusty in my combustion chemistry, but I hope that makes a little more sense...

Ah, very well then, I am clear that it is possible these fuels are burning more effectively which equals efficient heat transfer. I am interested, because in my limited experience, the BTUs do make a significant difference - the number for diesel at ~138,000 BTU/gal and a heavier oil like #4 with ~144,000BTU/gal doesn't look that significant, until you burn 100 gallons in an hour - then you will miss 600,000BTUs worth of steam making energy. But to your point, a lot depends on effectively burning the fuel you have in the system you are working with and maximizing heat transfer.
Thanks for the great discussion!

You are right in the amount of fuel being burned and BTU content...we haven't exactly switched the 3751 over from heavier fuels at this point with that being part of the reason - on long trips, fuel stops can be more of a pain to coordinate than water stops. I'm planning to talk to Jason more about the Disney World locomotives to get more information...

In the long term, however, it is nice to know that these fuels are viable so that if the heavy fuels become unavailable due to supply or environmental issues, we will still have options.

Would somebody explain to me what the cetane number (which is derived experimentally and reflects a theoretical stoichometric air fuel ratio ) has to do with combustion in a steam loco firebox-in excess air, of course.

Inquiring minds (at least this one) want to know.

DPK

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If I recall correctly, the Disney World locomotives would have previously been on regular diesel. One of the questions I would have for Jason regarding the marked improvement in fuel consumption would be if the air inlets had been altered in the fire pan...in which case, the 20% improvement would be skewed.

Guys, thanks for your responses. So if I am reading this the way I think it is headed, the question of whether this fuel really does have environmental and/or economic advantages when burned in a steam locomotive is still open.

So far none of the responses address the conparative economics of diesel vs. steam operation on this fuel. I think that is the first thing I would like to know if I was having to put together a business plan for a project.

MX

I read Wolf's statements using the Cetane Number as: "the measure of a fuel's ignition delay". http://en.wikipedia.org/wiki/Cetane_rating
So while burning any fuel oil in a locomotive firebox is obviously different than an internal combustion diesel engine, being able to measure the fuel's ignition delay is still a measureable qualitity that can be useful in comparing combustion. Generally, other fuels have other scales, so they are hard to compare and I don't know of a single quantifiable scale or measure for all fuel oil types.

Literally, yes, the Cetane number is only applicable to the components of diesel oils in a test environment. I don't think* (uhoh), it has to do with the stoichometric air fuel ratio.

MX - I don't think anyone can answer your question with results yet.

Sully, thanks for your comment. I suspected there was probably not an answer available when I asked it, but there needs to be one. People are already making statements promoting this fuel based on it providing some ecological and/or economic advantages, apparently without much research to back the claims. Sooner or later some reporter or somebody at EPA is going to ask for proof. It doesn't seem like a very good idea to be pumping something into a locomotive nowadays and have no knowledge of what is coming out the stack as a result.

If you burned peanut oil, or bio-diesel containing peanut oil, would you have to be concerned about passengers or crew with a peanut allergy?