How Does This Help The Environment?

[Maine farmer]

Recently the government mandated the use of ultra low sulfur diesel fuel. Before the mandate my VW Golf tdi regularly got 54 miles per gallon. After the switch to the "clean" diesel, I now rarely get better than 48. Additionally, the new fuel is corrosive to the gaskets in the fuel injection pumps on diesel engines, requiring additives to provide lubrication, and adding to the costs. So, is the world a cleaner place now, or does the government just want us to burn more fuel so they can collect more money in fuel taxes? I get so disgusted when I see advertisements for vehicles bragging about 35 miles per gallon. Shouldn't we be doing better than this? I used to have a 1980 model VW Dasher diesel that got 42 miles per gallon.

[CraigD]

How Does This Help The Environment?

Reducing sulfur in fuels such as coal and diesel helps the environment primarily through reducing the concentrations of compounds such as sulfur dioxide, primarily in urban areas where its concentration can reach level dangerous to at-risk people, and also the amount of sulfuric acid, which can damage plants, animals, and structures.

 

However, for diesel fuel in most countries, including the US these goals were reached decades ago. The current reductions in diesel fuel sulfur content (typically from 500 to 50 parts per million to less than 15 ppm, though current and target concentrations and implementation timelines vary widely among countries) is intended not as much to directly reduce sulfur emissions as to make it possible for vehicle and equipment manufacturers to install less expensive and more effective diesel particle filters.

 

Particle pollution from diesel engines, especially in urban areas, are a major factor contributing to preventable illness and death.

 

Before the mandate my VW Golf tdi regularly got 54 miles per gallon. After the switch to the "clean" diesel, I now rarely get better than 48.

I can't think of any chemical or mechanical reason that this should occur. Unlike additives such as lead in gasoline, the sulfur in diesel fuel shouldn't significantly effect its performance in an engine.

 

Before reaching this conclusion, farming guy, I recommend being careful to rule out other possibilities. Specifically, be sure that the pump gauge you're using is accurate. I've had personal experience with gasoline stations suddenly changing their pumps to dispense much less than the amount displayed on them, and been chagrined by the difficulty at getting operators, owners, or state regulators to correct it. You may still be getting the same millage, but getting less fuel than indicated at the pump.

 

Of course, check your car's diagnostics to be sure its not having a problem. They do that sometimes ;)

 

Additionally, the new fuel is corrosive to the gaskets in the fuel injection pumps on diesel engines, requiring additives to provide lubrication, and adding to the costs.

What additives are you using?

 

I've not heard this before, but have little experience with diesel engines other than large, fixed ones used for emergency electric generators. It seems reasonable to me that the refining processes being used to reduce sulfur in diesel might be removing something other than sulfur. Complaining to the big oil company that refined and mixed the fuel might get them to add whatever you're adding, sparing you and everybody else the trouble - and the engines of people who don't the wear!

 

So, is the world a cleaner place now, or does the government just want us to burn more fuel so they can collect more money in fuel taxes?

The world isn't a cleaner place for reducing sulfur in diesel fuel yet. The idea is that, once it's safe to do so because all US pumps dispense only ULSdiesel, carmakers will be able to add catalytic filters to diesel vehicles, and this will make the world (or at least the US) a cleaner place.

 

I don't think anyone in government is trying to increase tax revenues by reducing vehicle fuel economy, diesel or gasoline. According to an friend of mine at the EPA, increases in gas fuel price have in the past decade tended to decrease federal gas tax revenue, because people reacted by curtailing vehicle use so much that they collectively spent less on gas than before. This is, apparently, a basic supply-and-demand economic phenomena, and the primary reason sellers of fuel or any other commodity don't simply all (that is, conspire to fix and) raise prices to increase their revenue and profits.

 

I get so disgusted when I see advertisements for vehicles bragging about 35 miles per gallon. Shouldn't we be doing better than this? I used to have a 1980 model VW Dasher diesel that got 42 miles per gallon.

I get the same feeling.

 

I had a 1978 Plymouth Arrow (actually an imported and re-branded Mitsubishi) that consistently got 45 MPG. Part of this is that it was very light - barely a ton empty - but much of it was that it engine had some clever features, in particular high pressure air lines and valves that "swirled" the fuel air mixture in the cylinder prior to combustion.

 

Present day engines are much more powerful, reliable, and easier to maintain (I can diagnose my current vehicle, a 2000 Ford Windstar gas pig :(, in minutes with a $120 cable connected to my laptop - no mechanic's art to it at all!). They're not necessarily more efficient than some fairly old ones, though.

[Maine farmer]

A truck mechanic friend of mine tells me that the process used to remove sulfur from diesel requires that it be "run through watter", and I don't know the details, but if they are mixing the fuel with water, what are the odds that they are able to remove 100 percent of the water once it is mixed? The ultra low sulfur diesel, I have been told, provides a more hospitable environment for microbes that will clog filters, and John Deere is recomending use of( and selling, of course) pesticides to add to the fuel to prevent that problem. I also recently had to have some seals replaced in an injection pump on a 1996 model John Deere tractor, something we never had to do before even on 30 year old tractors. The nearby company that rebuuild injection pumps laid the blame with the ULS diesel.

[joekgamer]

How does a lower sulfur content increase the amount of microbes in the fuel?

[CraigD]

A truck mechanic friend of mine tells me that the process used to remove sulfur from diesel requires that it be "run through watter", and I don't know the details, but if they are mixing the fuel with water, what are the odds that they are able to remove 100 percent of the water once it is mixed?

I think this is an old mechanic’s tale caused by the name of the process used to remove sulfur from most petroleum products, “hydrodesulfurization” or “hydrotreating”. The “hydro” in this name refers to hydrogen, however, not water, so its better describe as “running diesel vapor through hydrogen gas”. As best I can tell, the only water in such a system is cooling water kept completely out of the reaction gas and liquid streams. (this wikipedia diagram gives as many details as I can digest)

 

The ultra low sulfur diesel, I have been told, provides a more hospitable environment for microbes that will clog filters, and John Deere is recomending use of( and selling, of course) pesticides to add to the fuel to prevent that problem. I also recently had to have some seals replaced in an injection pump on a 1996 model John Deere tractor, something we never had to do before even on 30 year old tractors. The nearby company that rebuuild injection pumps laid the blame with the ULS diesel.

These all appear to be real and common problems.

 

The microbe (or, more often, fungus) problem has long plagued biodiesel, which didn’t surprise me, as the “100% pure” forms of it is essentially food-quality cooking oil, and what is good for us to eat is surely good for many smaller plants and beasties, but that it’s become a problem in petroleum-derived ULSD fills me with amazement at the versatility and resiliency of microbes. Seems like the industry has the problem in hand, though my intuition is to favor filters over anti-fungal/microbial additives – nature’s pretty adept at beating pesticides, but a filter is pretty much unbeatable by anything too big to get through it.

 

I can't think of any chemical or mechanical reason that this should occur. Unlike additives such as lead in gasoline, the sulfur in diesel fuel shouldn't significantly affect its performance in an engine.

I couldn’t think of any last night, but reading more, found there are some, in addition to the microbe contamination Farming guy mentions.

 

Quoting the wikipedia article Ultra-low-sulfur diesel :

Sulfur is not a lubricant in of itself, but it can combine with the nickel content in many metal alloys to form a low melting point eutectic alloy that can increase lubricity. The process used to reduce the sulfur also reduces the fuel's lubricating properties. Lubricity is a measure of the fuel's ability to lubricate and protect the various parts of the engine's fuel injection system from wear. The processing required to reduce sulfur to 15 ppm also removes naturally-occurring lubricity agents in diesel fuel. To manage this change ASTM International (formerly the American Society for Testing and Materials) adopted the lubricity specification defined in ASTM D975[8] for all diesel fuels and this standard went into effect January 1, 2005

Again, the industry seems to be on top of the problem, but given how quirky and complex machines are, there’re bound to continue to be problems with ULSD for a generation or two of cars and other machines. From the same article:

It [uLSD] is, however, known to cause some seals to shrink and may cause fuel pump failures in Volkswagen TDI engines used in pre-2009 models. TDI engines from 2009 and on are designed to use ULSD exclusively; biodiesel blends are reported to prevent that failure

Of all the turbodiesels out there, you have to have the one known for ULSD killing, eh Farming guy?

[Maine farmer]

Thanks to everyone for the input! I came here to learn. I sometimes wonder if all the mandates are thought through thoroughly before they are imposed upon us. There will always be unintended consequences

[Maine farmer]

While I was out in the barn doing my chores, I was thinking about the "hydrodesulferization" process and how it might work. It's been a long time since my last chemistry class in college, but if they are using hydrogen to bind with the sulfur to remove it from the diesel fuel, wouldn't that make hydrogen sulfide gas? If so, what do they do with that?

[CraigD]

While I was out in the barn doing my chores, I was thinking about the "hydrodesulferization" process and how it might work. It's been a long time since my last chemistry class in college, but if they are using hydrogen to bind with the sulfur to remove it from the diesel fuel, wouldn't that make hydrogen sulfide gas? If so, what do they do with that?

I don't have any real familiarity with refinery chemistry, and have only the usual high school and undergraduate college chemistry education, so I'm just regurgitating wikipedia here, but, ... regurgitate wikipedia:

The hydrogen sulfide removed and recovered by the amine gas treating unit is subsequently converted to elemental sulfur in a Claus process unit or to sulfuric acid in a wet sulfuric acid process or in the conventional Contact Process.

Sulfuric acid and elemental sufur are commodity chemicals – they’re useful in many industries, so any increases in their production, result in decreases in the cost of many products, so having more of them is good. :thumbs_up