Flower Power: Electricity from Plants
By Don Willmott
It may sound like an idea dreamed up at Woodstock with the help of some mind-altering substances, but researchers are finding ways to tap into the power of photosynthesis to generate at least small amounts of electricity. As it turns out, plants are more efficient than they need to be, and they disperse excess energy that we can collect. Are we talking about megawatts from marigolds? Not exactly, but beyond the raw science are practical applications that shouldn’t be dismissed out of hand.
Dutch researchers at Wageningen University first patented the process of collecting plant power in 2007, and today those patents are in the hands of a Netherlands-based company called Plant-e, which is trying hard to productize the natural processes that make it all happen.
What’s actually going on down there in the dirt? In photosynthesis, a plant’s leaves absorb sunlight and blend its energy with water and carbon dioxide to make the sugars on which the plant feeds. What’s interesting is that the plant usually makes too much, dispersing perhaps half of its food into the soil. Once there, bacteria break down the sugars, and protons and electrons are among the resulting byproducts.
Plant-e’s idea is to insert a conductor into the soil to collect the electrons, which are then turned into electricity. The company says the process doesn’t interrupt plant growth; the plants just continue to reach for the sky. It’s renewable and sustainable. The only glitch: the process doesn’t work when the ground freezes.
So let’s talk numbers. Plant-e says that a one-square-meter garden should be able to produce 28 kilowatt-hours per year, which means that an average American house might be able to be powered by several thousand square feet of active growth. That’s not practical, but there are countless places around the world where people live in much smaller homes and have much lower energy demands. And many of the 1.4 billion people worldwide who don’t have access to electricity are active farmers or gardeners.
Plant-e also has its eye on temperate wetlands, peat bogs, mangrove swamps, river deltas, and rice paddies where it could generate power at scale for things like Wi-Fi hotspots, mobile chargers, and nighttime lighting to provide real benefits in poorer locales. For cities, Plant-e is testing modular green rooftop systems, 15 square meters of which would be enough to charge a cell phone. That may not sound exactly earth-shattering, but every little bit helps.
Don Willmott is a New York-based journalist who writes about technology, travel, and the environment for a wide variety of publications and websites.