HOUSTON (Dec. 12, 2013) Blending more ethanol into fuel to cut air pollution from vehicles carries a hidden risk that toxic or even explosive gases may find their way into buildings, according to researchers at Rice University.
Those problems would likely occur in buildings with cracked foundations that happen to be in the vicinity of fuel spills. Vapors that rise from contaminated groundwater can be sucked inside, according to Rice environmental engineer Pedro Alvarez. Once there, trapped pools of methane could ignite and toxic hydrocarbons could cause health woes, he said.
The timely warning comes as the United States works to stimulate the production and consumption of ethanol. The Rice study, detailed this week in the American Chemical Society journal Environmental Science and Technology, emerges as the Environmental Protection Agency (EPA) prepares technical guidance for higher ratios of ethanol in fuels.
"The safe distances (between buildings and groundwater) that the EPA are setting up are going to work well 95 percent of the time," said Alvarez, a member of the agency's Science Advisory Board. "But there's the 5 percent where things go wrong, and we need to be prepared for extreme events with low probability."
Computer simulations at Rice determined that fuel with 5 percent or less ethanol content does not rise to the level of concern, because small amounts of ethanol and benzene, a toxic, volatile hydrocarbon present in gasoline, degrade rapidly in the presence of oxygen. Methane produced when ethanol ferments is often degraded by methanotrophic bacteria, which also require oxygen.
But fuel blends of 20 to 95 percent ethanol and gasoline, intended for "flex-fuel" vehicles, could increase the generation of methane. Ethanol and gasoline separate into distinct plumes as they spread underground from the site of a spill. As liquid ethanol degrades into gaseous methane, it expands, driving advective f
|Contact: David Ruth|