MTBE faces a new round of political skirmishes in the U.S.

Barbara Saunders
Staff Writer

After a brief hiatus in 1996, scientific and health controversies are swirling anew around methanol-based MTBE.

In the U.S. Congress, meanwhile, advocates of corn-based ethanol oxygenates are again warring with lawmakers who seek to eliminate price supports and tax subsidies for ethanol (OGJ, Mar. 24, 1997, p. 22).

Air quality mandate

Legislative prohibitions against MTBE would make it either impossible or prohibitively costly for many states to meet requirements of the U.S. Clean Air Act amendments of 1990, analysts say.

The law requires 2 wt % oxygen content in reformulated gasoline (RFG), which is now mandatory in 10 of the most heavily-polluted U.S. metropolitan areas. It can be used voluntarily in about 20 others with less severe air quality problems (OGJ, Jan. 6, 1997, p. 18). In addition, many areas not required to use RFG must use oxygenated gasoline during October-March, to reduce emissions of carbon monoxide. These gasolines typically contain 2.7 wt % oxygen, which translates to about 15 vol %.

Controversial past

MTBE has become the favored oxygenate, primarily due to the relatively low cost of its primary feedstock, methanol.

It had been in use as a wintertime oxygenate since the late 1980s, starting in Colorado, and was used by refiners as an octane-enhancer before this. Complaints of engine troubles and safety/health concerns arose early in the 1990s. Alaska barred sales of gasoline containing MTBE late in 1992 after motorists complaints of headaches they thought were linked to the additive (OGJ, Mar. 15, 1993, p. 36). However, when federal-specification RFG was introduced to market in January 1995, the use of MTBE drew an unexpectedly widespread backlash (OGJ, Feb. 13, 1995, p. 17).

The rash of complaints triggered about $2 million worth of studies, but none established a decisive link between MTBE and either health or engine problems (OGJ, Jan. 8, 1996, p. 34).

The National Research Council (NRC), Washington, D.C., last year issued a report assessing all studies to date, finding they had deficiencies in the analysis of health effects, including "inadequate exposure assessment, insufficient sample size, subjective outcome assessment, and the possibility of a skeleton bias." It also concluded that "engine performance is typically not affected by the use of oxygenated fuels."

New furor

The furor over MTBE that kicked up just after its 1995 debut had eased long before NRC issued its findings, but concerns escalated anew last year, after MTBE was found contaminating groundwater around storage tanks and gasoline stations in Colorado (OGJ, Apr. 17, 1995, p. 21) and later California.

The Western States Petroleum Association helped fund a new study on this problem, and few in the industry disputed the potential significance, because cleanup of methanol contamination is extremely difficult.

Some in the industry believe such contamination is not a recent phenomenon and could stem from state and local permits being granted for gasoline stations located too close to aquifers back when MTBE was merely an octane enhancer.

"Authorities should not have granted permits so close to drinking water sources," said Cal Hodge, technical chairman of the Oxygenated Fuels Association, Washington, D.C., and manager of market and regulatory analysis for Valero Energy Corp., San Antonio.

Hodge says studies show MTBE concentrations well below the U.S. Environmental Protection Administration's 70 ppb groundwater standard, typically in the 10-30 ppb range. Higher than this, "a person's own senses will help keep him safe," Hodge maintains, for MTBE has a distinctive smell that will be detectable long before hazardous concentrations are reached.

Legislative bans

Nevertheless, attempts to ban MTBE use are mounting.

A measure was recently introduced in California's legislature calling for a ban on MTBE (OGJ, Mar. 10, 1997, Newsletter), and a similar measure is under consideration in Maine, which would allow the state to opt out of the federal RFG program over MTBE-related health concerns.

At the other end of the spectrum, Nebraska is mulling increasing the oxygenate requirement in the state's gasoline to 2.7 wt % minimum statewide. Nebraska, at the center of the corn belt, also has been behind longstanding efforts to require use of ethanol and ethanol-based oxygenates in RFG.

What's the future of prohibitions on MTBE? Insiders predict little to no chance of passage.

Barney Parsons, analyst for U.K.-based consultants Douglas-Westwood Ltd., said, "Attempts to ban MTBE have been seen before. I do not think that efforts to legislate a ban will succeed in getting very far...The evidence of improved air quality in the U.S. resulting from oxygenated RFG seems very strong, and it would be difficult to create a driveable RFG without oxygenate, although theoretically possible. These attempts may relate as they have in the past to the ethanol lobby, who may be trying to get ETBE (ethyl tertiary butyl ether), or even ethanol, as the oxygenate of choice.

"It seems that ethanol producers may be losing their 5.4¢/gal tax break in 1999," Parsons said. "Maybe the anti-MTBE lobbying at this time may help to result in a compromise protecting the viability of increased ethanol capacity in the Midwest."

While health concerns continue to be raised about MTBE, at least extensive testing has been conducted and continues today, OFA's Hodge points out. Ethanol-based ETBE is virtually untested, he notes.

Status of testing

NRC's report said monitoring data isn't sufficient to know the full extent of groundwater contamination.

The data available showed that MTBE was "detected in less than 5% of the groundwater samples analyzed, suggesting that drinking water is not currently a major exposure pathway...for much of the population."

NRC said, "More needs to be known about the biodegradation of MTBE and other alkyl ether oxygenates in surface water, soil, and groundwater.

"Biodegradation processes, in particular, have the potential to substantially reduce the impacts of...releases of MTBE and other oxygenates."

While NRC did not seem convinced of a link between MTBE and flu-like symptoms in motorists, it did urge further studies to determine potential hazards to workers with long-term exposure to high concentrations of the oxygenate.

Environmental benefits?

In addition, NRC urged new studies to determine the extent to which oxygenated fuels actually reduce wintertime CO concentrations in the air.

It believes that EPA's model "overpredicts the oxygenated-fuel effect by at least a factor of two" and that other steps, such as incentives to remove old-model cars from the road, may be just as or more effective than requiring oxygenated fuels.

NRC also found that "increased NOx (nitrogen oxides) emissions may have resulted from the use of oxygenated fuels. Any increase in NOx emissions could be detrimental in ozone nonattainment areas where exceedances have occurred during the period of the oxygenated-fuels program," the report said.

"A well-designed study with adequate statistical power should be performed at low temperatures to assess whether oxygenated fuels reduce ambient CO concentrations under such conditions," NRC advised.

Depending on results, further research should examine how oxygenated fuels affect NOx, VOCs (volatile organic compounds), and toxic air pollutants in the winter, it said.

Many in the industry believe that controversy over MTBE will wax and wane periodically until all long-range testing is finished. "Eventually science will catch up, and people will rest easier," predicts Hodge. "People always get frightened when something is new and legislators start doing weird things."

Copyright 1997 Oil & Gas Journal. All Rights Reserved.