ScienceDaily (Sep. 9, 2009) — You've heard about flower power. What about tree power? It turns out that it's there, in small but measurable quantities. There's enough power in trees for University of Washington researchers to run an electronic circuit, according to results to be published in an upcoming issue of the Institute of Electrical and Electronics Engineers' Transactions on Nanotechnology.
http://www.sciencedaily.com/releases/2009/09/090908151330.htm