Coming up with a definition of diesel fuel seems like a fairly straightforward task, but in the world of natural gas drilling and the process of hydraulic fracturing – or fracking – nothing ever comes easy. Senior Colorado Congresswoman Diana DeGette on Monday joined fellow Democrats Henry Waxman, Edward Markey and Rush Holt in asking the U.S. Environmental Protection Agency (EPA) to write a much broader definition of diesel fuel than the industry seems willing to accept.