By Miku Suga, '22
Renewable, safe, and sustainable energy production that meets the demands of the increasing human population will always be the ultimate goal of the energy industry. Only 12.5% (as of 2015) of the global energy consumption is contributed by the renewable resources (main examples include hydroelectric, solar, and wind power), and it is still essential to look out for ways in which reliable energy could be generated.  Plant-Microbial Fuel Cell (P-MFC), a fascinating example of sustainably generated energy, was proposed in 2009 by the sub-department of Environmental Technology at Wageningen University in Netherlands as their project “Plant-e”, and it is worth discussing its advantages and how shortly it could be widely used in the world. 
The concept of P-MFC is simple: it represents a “battery”, incorporating both the plant and the bacterias surrounding the root system. First, the leaves undergo a natural process known as photosynthesis, which converts light energy from the sun into chemical energy, with the help of water and carbon dioxide taken from the atmosphere. Glucose is produced, assembled, and converted to larger macromolecules, as it is transported through vascular systems to different organs and ultimately used for growth. Roots innately excrete some of these sugar molecules into the soil, which results in satisfying the diet of naturally occurring bacterias that occupy the space. The by-products of the bacterias that feed on the sugars are electrons and protons; and it is these electrons that are collected as the anode. Those electrons travel to the cathode from the anode, via wires set up by people, producing electricity. 
One of the advantages of P-MFC is that it is carbon dioxide negative. Carbon dioxide largely makes up the greenhouse gases, and its emission (e.g. from burning oil, coal, wood, and gas) largely affects the earth’s surface temperature and climate.  Granted the bacterias do produce carbon dioxide as a consequence of its respiration, as this natural emission occurs independently of energy production. The other benefit of this plant battery is that the only ‘waste’ product of the entire process is water; at the end of the process, the electrons that have moved to the cathode will combine with the oxygen in the air, forming water molecules that are released back into the soil. 
P-MFC is widely set up in plants that grow in waterlogged conditions, since it conveniently avoids oxygen intrusion from the air into the anode. Thus many grassy species, including rice paddy fields, can adopt this P-MFC structure, theoretically producing 3.2 W per meters squared.  Though it may not produce as much energy per area as other existing renewable resources, such as wind and solar power, if P-MFC were to be implemented in already-existing gardens, parks, and paddy fields on a larger scale, it could and will contribute significantly to the electricity generation technology.
1. “U.S. Energy Information Administration - EIA - Independent Statistics and Analysis.” How Much of World Energy Consumption and Production Is from Renewable Energy? - FAQ - U.S. Energy Information Administration (EIA), www.eia.gov/tools/faqs/faq.php?id=527&t=1.
2. “Kurzweilaccelerating Intelligence.” NextGEN Gallery RSS, www.kurzweilai.net/plant-e-root-shoots-leaves-electricity-from-living-plants.
3. “Information and Technology.” Plant-e, www.plant-e.com/en/informatie/.
4. “Carbon Dioxide (Co2) Emissions.” Wikiprogress, wikiprogress.org/articles/environment/co2-emissions/.