Gaining Traction

The nation's underground mines are turning to biodiesel to reduce diesel particulate matter levels to help comply with tighter air quality limits.
By Susanne Retka Schill | April 15, 2008
When it comes to underground mines, the puff of black smoke emitted by diesel engines is an image that may soon be delegated to the history books. As of May 20, metal and nonmetal underground mines are required to reduce miners' personal exposure limits to diesel particulate matter (DPM) to a level where engine exhaust would barely be visible. A number of measures can be taken in a mine to achieve this including replacing old engines with the newer, low-DPM engines, fine-tuning diesel maintenance and using exhaust filters. Personal exposure can also be reduced by boosting ventilation rates in mines and installing sealed, environmental cabs on heavy equipment.

Switching to higher biodiesel blends is becoming a popular solution to reduce DPM levels, and in some cases, it's the only solution. In 2001, when the regulations were first proposed, a number of studies were done in mines, says Richard Nelson, director of engineering extension at Kansas Sate University. "They found that biodiesel took you from where you were, closer to these personal exposure limits in a big chunk." Bill Pomroy a spokesman for the Mining Safety and Health Administration says inspectors have seen DPM levels drop from 300 to 800 micrograms per cubic meter of air to 50 to 200 micrograms. The only change that was made was to switch from straight diesel to B100 (see charts on page 71).

As the May 20 deadline approaches, some mines are already in compliance, dropping DPM levels to 160 micrograms per cubic meter of air, while others struggle, according to Pomroy. There are fewer than 200 metal and nonmetal mines (basically all mines that aren't coal mines) in the United States. Materials mined underground include gold, platinum, gypsum, limestone, salt and potash.

The Renewable Energy Group Inc. headquartered in Ames, Iowa, has been supplying biodiesel to one underground mining customer since 2004. Jon Scharingson, REG's director of marketing, says 15 to 20 mining companies across the country are already using biodiesel blends at some level. Because several of those companies operate multiple mines, those mining companies would represent 20 percent to 30 percent of underground mines currently using biodiesel. That leaves plenty of room for growth. "We'd anticipate that number increasing dramatically over the next six to 12 months," Scharingson says. The future looks even brighter as the mining industry is growing in response to record-high commodity markets.

Compliance charts from two mines show the difference in DPM exposure levels after introducing B100. The data is gathered by placing monitors on mine employees to measure their personal exposure. The charts show the levels of personal exposure to elemental carbon in micrograms per cubic meter of air, with each miner monitored indicated with a circle. The one data point for biodiesel above the dotted blue line in Mine B demonstrates that in some instances biodiesel alone will not be able to get the personal exposure limits to the mandated level.

The good news for biodiesel producers is that this growing market has the potential to use large quantities of biodiesel. In studying the mining market for the National Biodiesel Board, Nelson found Census Bureau data that indicates this group of mines uses 500 million gallons of distillates each year. Biodiesel will not replace all distillates, and not all mines are listed in the data because categories with just one or two players are not reported, he says. "A couple of mining companies we've had discussions with are using about 1 million gallons a year," Scharingson says, "It's not insignificant volumes we're talking about. Its lots of pieces of heavy equipment they're running around the clock."

Underground Experiences
In Iowa, Martin Marietta Materials Inc. owns five limestone mines that operate eight to 14 pieces of equipment underground at any time, ranging in size from 5- to 9-yard loaders, 40- to 60-ton trucks, drills and other diesel-powered equipment. "We tried various lower [biodiesel] blends with mixed results-5 percent, 10 percent, maybe up to 20 percent," says Todd Clock, vice president, general manager of the Des Moines district. "Once we found that it didn't do a lot for us, we went to B99 in late 2005." Filter plugging was the only problem that emerged initially during the transition. That was taken care of by installing a filter on the storage tank. Winter cold storage isn't an issue because the fuel can be stored underground.

Despite the success the company has had using biodiesel, there are some issues that need to be addressed. "My biggest concern now is cost," Clock says. "It certainly has become very expensive." High prices, and the possibility that the price of biodiesel could continue to rise for an extended period of time, prompted him to evaluate other options such as adding ventilation shafts. "We thought we had found the magic bullet," Clock says. "We did for a time." Even though it's not cheap to add a ventilation shaft, it may pay for itself in the long run if fuel costs continue to climb, he says.

Ironically, the renewable fuel is sometimes hard to procure, even though Marietta Materials' limestone mines are in the heart of biodiesel country. "There were some fuel shortages off and on in the summertime," he says. "[Our suppliers] would say, 'We're running low' or 'We can't get a tanker in for a week.' If I have any concerns, it may be we may not have the raw product available as soybean oil continues to be in high demand."

The Stillwater Mining Co. in south central Montana has one of the nation's largest underground diesel fleets, says Rick Collins, stationary maintenance superintendent and the company's DPM reduction project champion. The mining company runs 340 pieces of equipment with engines that range from 13 to 400 horsepower. After participating in biodiesel studies in 2003 and 2004, the company has been using B50 since April of last year. "Biodiesel alone doesn't achieve our goal, but assists in reaching the final limit," Collins says.

Stillwater Mining is combining B50 fuel with exhaust treatments to meet DPM limits in its palladium/platinum mines. While some mines rely on biodiesel alone, Collins says it makes more sense to combine soot filters with biodiesel because the improvements from biodiesel begin to level out at higher blends. "B20 has reductions at around 20 percent and B50 around 50 percent, but the gain in DPM improvements appears to tail off above 75 percent," he says.

Like Clock, Collins also experienced some minor issues when the mine switched to biodiesel, with cost being the No. 1 concern. Interestingly, the surface operators notice a drop in performance while using the biodiesel blend when compared with No. 2 diesel. However, the company hasn't had any problems nor seen any big difference in engine performance when compared with No. 1 diesel. The company also had to make sure gaskets and hoses were upgraded to biodiesel compatible materials. "We had one minor issue where a hose didn't get changed on a fuel tank, and they recognized it before it blew out," he says. Stillwater Mining also found it challenging to find reliable supplies and a supplier willing to do what was needed to supply biodiesel year around.

Myth Busting for New Users
Scharingson says REG hasn't heard many complaints about winter biodiesel use primarily because the temperature in underground mines is generally a stable 50 degrees Fahrenheit.

Equipment performance issues have also been minimal, he says. "We haven't heard any significant technical issues running biodiesel at 50 percent, 75 percent or 100 percent levels in this heavy construction equipment," he says. "The major OEMs (original engine manufacturers) supply this equipment-Caterpillar, Komatsu and Cummins-and we've been seeing good results in terms of performance, energy utilization and, obviously, the DPM reduction. There have been no negative reactions in terms of how the heavy equipment works at high percentages of biodiesel."

One of the biggest hurdles that must be overcome for biodiesel producers to get a stronger foothold in the mining market is to make operators aware of the fuel and to educate them on its benefits. "Biodiesel is a new fuel and they're not that familiar with it," Scharingson says. "To some extent we're doing myth busting. Once you sit down with them-most are engineers-and explain that this is similar to petroleum-based fuel products and talk about the attributes of the fuel and the parameters of the ASTM spec and our own internal
specs that REG has, they get very comfortable with it very quickly." Outside of the Midwest, in particular, there are misperceptions about cloud point and fuel gelling. "They just need education so they understand if the proper handling guidelines are in place, it's very similar to handling diesel fuel," Scharingson says.

Nelson has been fielding calls from mines that are considering a switch. "The calls we get are on fuel quality, engine performance, warranties and how to handle B100," he says. He advises them to verify fuel quality by getting a certificate of analysis from the petroleum distributor showing that the fuel meets ASTM specifications and has acceptable cloud points. Maintaining quality in storage has not been an issue. "They turn the fuel over quickly," he says. As far as engine warranties are concerned, Nelson reminds questioners that OEMs don't warranty any fuel. "They don't warranty 100 percent diesel fuels either," he says. "They don't make the fuel-they don't supply the fuel." While the uninitiated have questions, Nelson adds, "Everybody I've talked to has had a pretty easy time making the transition."

Nelson wants to study the mining industry's transition to higher biodiesel blends. While MSHA has data from studies showing the impact of biodiesel on personal exposure to DPM, he would like to document the impact, if any, on the equipment after the switch to B100 and provide that information to the NBB and the U.S. DOE. He submitted a proposal to collect data from a representative sample of mines to compare records on performance and maintenance before and after the switch to B100.

Susanne Retka Schill is a Biodiesel Magazine staff writer. Reach her at or (701) 738-4962.
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