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. Voltree Power has built a “bioenergy converter” that parasitically harvests metabolic energy from trees.
The available energy is certainly not enough to make a dent in human consumption. However, according to the Technology Review article, enough energy is available to power wireless mesh networks within forests that can transmit data about local temperature and humidity conditions. These networks could be used for agricultural monitoring or early detection of forest fires. Voltree Power is planning to test their so-called Early Wildfire Alert Network (EWAN) beginning in the spring.