For those with interest in using invasives as biofuels, I ran 
across this 2007 presentation earlier today. The estimate 
($28/ton) they give for dry mass cost seems pretty optimistic, but 
even double that amount would be pretty good - particularly if 
credit was also given for the mass of nutrients removed from a 
water body.

http://www.rpi.edu/dept/chem-eng/design/pdf/Jessica%20Hronich.pdf

--
Jason M. Evans, Ph.D.
Postdoctoral Researcher
Department of Wildlife Ecology and Conservation
University of Florida
Newin-Ziegler 319
(352) 846-0148 - office
(352) 328-1199 - cell