Plants produce such enormous quantities of organic material from photosynthesis that they actually excrete 70 percent of it, unused, into the soil by their roots. This provides important nutrients for bacteria and other soil organisms. When bacteria metabolize this organic matter, they release electrons into the soil. The premise of the Plant-Microbial Fuel Cell is that electrodes placed close to the roots of plants can absorb these electrons and use them to generate electricity, much like a battery.

Helder's tests indicate that the Plant-Microbial Fuel Cell can generate 0.4 W of electricity per square meter of vegetated area, more than biomass fermentation is currently capable of. Through further refinement of the technique, Helder predicts that its power generating capacity could rise as high as 3.2 W per square meter. This level of power generation would enable the average household to be supplied entirely from the power generated by grass planted on a 100 square-meter roof.