MTBE is a gasoline additive thought to make its way into drinking water and cause cancer. The big issue with MTBE, the chemical methyl tertiary-butyl ether, is it mixes easily, although sparingly, with water. If gasoline containing MTBE leaks from an underground tank at a gas station, it can get into groundwater and contaminate wells. Of course, MTBE isn’t the only thing getting into the groundwater when a tank leaks – so are gasoline and all the other gasoline additives. But in the past two decades, especially in the U.S. MTBE has been singled out as the worst of the gasoline fuel package.
The news is the specialty chemical company Evonik has introduced a bio-derived version of MTBE. The bio version is made from raw glycerine, which is a co-product of the biodiesel manufacturing process.
MTBE progress is important because it boosts octane and is an oxygenate, meaning that it adds oxygen to the reaction when it burns. For gasoline consumers in the U.S. MTBE came too late to save thermal efficiency when lead was taken out of the gasoline package in the 1970s. The necessary removal of lead was a necessary thing, but the lack of an instant replacement left engines with drastically dropped compression ratios and fuel economy. The U.S. has yet to fully recover from the bureaucratic blunder.
Today the Environmental Protection Agency says, “Although there is no established drinking-water regulation, USEPA has issued a drinking-water advisory of 20 to 40 micrograms per liter (µg/L) on the basis of taste and odor thresholds. This advisory concentration is intended to provide a large margin of safety for noncancer effects and is in the range of margins typically provided for potential carcinogenic effects.”
After 1990 MTBE started getting added to U.S. gasoline when the Clean Air Act of 1990 went into effect. For a decade U.S. gasoline might have contained as much as 10% to 15% MTBE.
MTBE is pretty good stuff – it improves gasoline combustion, helps prevent engine knocking and decreases carbon monoxide and other emissions from vehicles. Conventional MTBE is manufactured via the chemical reaction of methanol and isobutylene.
Evonik began producing Bio-MTBE in March 2012 from isobutene and biomethanol in Marl (Germany) along with conventional MTBE. Bio-MTBE possesses the same technical attributes as its conventional counterpart: high energy density (86% of gasoline), low vapor pressure, low oxygen content, and very low solubility in water. It also means that Bio-MTBE can be handled safely in refineries and storage tanks and be conveyed by pipeline.
Evonik has sold Bio-MTBE primarily in Germany and the Netherlands. The implementation of EU directives in other member states points toward additional growth potential for the Bio-MTBE. Current European gasoline specification allows up to 15% by volume of MTBE and the revised EU Fuels Quality Directive enables the specification to be expanded to up to 22% by volume for MTBE in gasoline. If market demand grows Evonik can shift the full capacity of its 550,000 metric tons per year plant over to production of Bio-MTBE.
Back in the U.S. MTBE was used in gasoline at low levels beginning in 1979 to replace lead as an octane enhancer. Beginning 1992, MTBE has been used at higher concentrations to fulfill the oxygenate requirements established in the 1990 Clean Air Act Amendments.
But by the late 1990s a number of community drinking water samples were analyzed with detectable levels of MTBE. That led to many areas phasing out MTBE use in gasoline, commonly replacing it as an oxygenate with ethanol. Abut half of the states in the US subsequently passed laws limiting or banning the use of MTBE in gasoline.
Evonik isn’t saying the Bio-MTBE is any different from conventional MTBE, so it’s probably not chemically unique. For U.S. consumers getting a useful supply is probably out of the question.
But there is a good-sized lake of glycerine from U.S. biodiesel production that has a market possibility, albeit an export market. Exported the glycerine would benefit the world fuel market. It’s a pity the trial lawyers and special interest hysterics have cut the U.S. out of the market.