I'm in Arlington (Rosslyn) as well, although I live in Silver Spring.
I've been toying with going into homebrew biodiesel production in accordance with the Bill Kemp tome. See Amazon reference. Also available at local libraries.
http://www.amazon.com/Biodiesel-Basics-Beyond-Comprehensive-Production/dp/0973323337/ref=pd_bbs_sr_1/105-8286965-1597266?ie=UTF8&s=books&qid=1192829059&sr=8-1
Kemp's set up meets US ASTM standards. Book is an interesting read, half bashing home brewers, a quarter on how important it is to meet a national standard, the rest on how he put together a rig to do just that.
Sunk costs for the tanks and pumps aside, the claim is made that B100 meeting spec, and that can be used year round in cool to cold climates, can be produced for 85 cents a gallon.
Add in costs of swapping out rubber fuel lines, of course.
A GTG to compare notes on fuel, parts, techniques, etc. would be interesting.
Off to Africa for a week beginning Tuesday, but will be able to check this forum.
Hope to see you folks...