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. Vapours that rise from contaminated groundwater can be sucked inside. Once there, trapped pools of methane could ignite and toxic hydrocarbons could cause health woes, according to Rice environmental engineer Pedro Alvarez.
The timely warning comes as the United States is promoting the production and consumption of ethanol through higher ratios for ethanol in fuels.
When ethanol is spilled into the soil, bacteria from fermentation breaks liquid ethanol down into methane gas, which expands as it diffuses. The fuel also produces benzene, a toxic hydrocarbon and known carcinogen, which can leach into homes.
“The safe distances (between buildings and groundwater) that the EPA are setting up are going to work well 95 per cent of the time,” said Alvarez. “But there’s the 5 per cent 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 per cent 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. But fuel blends of 20 to 95 per cent ethanol and gasoline, intended for “flex-fuel” vehicles, could increase the generation of methane.