What began as a study of how trees generate electricity may end up protecting forests from fires.

For decades, scientists have known that trees and their surrounding soil produce a small amount of electricity, but the reason for the phenomenon has been the subject of much debate. To put that debate to rest, Christopher Love, a senior chemistry major at MIT, worked with Shuguang Zhang, associate director of MIT's Center for Biomedical Engineering, and Andreas Mershin, a postdoctoral associate at the center, to test the various theories. Their results, published recently in the journal Public Library of Science One, support an explanation not previously considered: that the difference in pH levels between a tree and the surrounding soil is what allows the tree to produce electricity. "If there is a difference in pH between the tree and the soil, then you will observe a voltage from that difference by putting same-metal electrodes in each," explains Love.

Armed with this information, Voltree Power in Canton, MA, is working to use that electricity to help predict forest fires.

Today, the U.S. Forest Service gets environmental information from solar-powered units located in forest clearings, says Love. The system Voltree is producing will send data from within the forest, providing more accurate details about conditions.

Voltree, in which Love and Mershin have a financial interest, will use a bioenergy harvester to collect energy from the tree, a sensor to gauge temperature and humidity, and a wireless mesh network to transmit the data. The sensing and harvesting units can be installed easily and then left alone: the sensors' batteries will be recharged by the electricity the trees produce. "The tree energy that we're getting is very small," says Love. "But that's better than no energy."

Starting this spring, Voltree will test its device in a 10-acre area provided by the U.S. Forest Service in Boise, ID. Future applications, Love says, could include agricultural monitoring as well as radiation detection along the U.S. borders, to prevent the smuggling of radioactive goods.