U.S. Maritime grant aims to find cleaner river towboat engine

Liquefied natural gas, with a simpler chemistry of just methane molecules, will burn cleaner than the complex hydrocarbon molecules that comprise diesel fuel. “When you burn something complex, you have lots of incomplete combustion,” said Gwen DiPietro, adjunct engineering professor at Carnegie Mellon University who studies towboats and is an EPA consultant. “With natural gas, it’s a simpler soup.” In 2010, she found that diesel towboat traffic in Allegheny County emitted 23 tons of tiny particulate matter smaller than 2.5 microns, known as PM 2.5, that year. To compare for scale, the Allegheny County Health Department recorded that all point sources in the county emitted a total of 1,026 tons of PM 2.5 in 2010. These fine breathable particles are smaller than the diameter of a human hair.