Trees have been providing energy for humans since before
recorded history. Cavemen used fire to release the stored energy
in wood to cook food and provide illumination at night. Medieval
castles were heated by massive wood-burning fireplaces. Wood
burning locomotives helped connect the Atlantic and Pacific by
rail in the 19th Century. Today, trees continue to be an
important store of energy for humans.Throughout our long history
of using trees for energy, the primary means of releasing that
energy has been combustion. I was very interested, therefore, to
read “Trees, Save Yourselves” in Technology Review. Researchers
at MIT, led by Dr. Shuguang Zhang, have hit upon an alternative
means of extracting energy from trees without setting them on
fire. By harnessing the pH difference between trees and the soil
in which they are rooted, a small amount of electricity can be
generated. While this phenomenon has been observed for years, a
company is now capitalizing on MIT’s research to power sensor
networks in forests