Gerard's statement was, in part, "Today, most ULSD is produced by treating the fuel with hydrogen to remove sulfur and other impurities. Most of that hydrogen is produced directly from methane contained in natural gas. Yet federal policies continue to put most U.S. natural gas supplies off-limits. If the nation is to be successful in our pursuit of cleaner diesel fuel, then Congress needs to change energy policies to help bring about reliable, affordable access to natural gas."
If you're interested in the details of diesel hydrotreatment possibilities, check out this article from when the Department of Energy looked at the issue of ULSD techniques in 2001.
[Source: American Chemistry Council]