How do Photo-MFCs work and why are mosses so suited for it?
In order to grow, plants photosynthesise - they use solar energy to convert water and carbon dioxide into sugars.
The photosynthetic process, in simple terms, consists of two stages. In the first, light-dependent stage, plants split water - oxygen is released and electrons and protons are produced. In the second, light-independent stage, plants then ingest carbon dioxide to convert those electrons and protons into sugars.
Now, here’s why mosses operate as potentially better photo-active components in Photo-MFCs than other plants: Mosses are as efficient in the first stage of photosynthesis as other plants. But they grow slowly, which means they are less efficient at converting the produced electrons and protons into sugars in the second stage - leaving us with bigger potential to collect and transform electrons into electrical current.
And because the plants store what they have produced, we can harness electricity from mosses even when there’s no light for a while.
Photo-MFCs is an emerging technology and still in its infancy. Although we understand how it works, we can currently harness only a tiny fraction of the electrons produced. Further research is concerned with making microbial fuel cells more efficient.
Illustrations: Fabienne Felder, 2013