Interestingly enough, Denton County, Texas has recently unveiled their plan and it's "success" for alternative fuel sources. It's not a new discovery, but they are one of the first in the nation (or at least local news sources say so) to take advantage of bio-diesel. They made a $650,000 USD investment in using methane gas captured from landfills and refined/recycled restaurant grease to produce bio-diesel for all the counties vehicles. Presently they are able to supply the fuel to themselves for about $1 USD/gallon. Part of the longer term plan is to produce more than the county can use in it's vehicles and sell to other sources. They believe the $650,000 investment will pay off quite quickly with the rate at which fuel prices are rising.