Using blue-green bacteria, researchers have for the first time developed a way to convert sun light directly into electricity in a CO2-free manner.

The study illustrates that electrogenic workings of cyanobacteria is an important conduit of solar energy into the biosphere, says associate professor Ilia Baskakov, PhD. Center for Biomedical Engineering and Technology at the University of Maryland, Baltimore (UMB) Baskakov, who led the study, says that such findings could lead to ways to generate energy in a self—sustainable manner using renewable resources. “Climate change related to global warming and the demand for energy are two of society’s most pressing problems and both can be solved if new technologies are developed,” says Baskakov.

The UMB researchers discovered that cyanobacteria possess a natural light-dependent electrogenic activity. The bacteria can generate and transfer high-energy electrons -- generate electricity -- to the external environment under illumination. Cyanobacteria fix within themselves an estimated 25 Giga tons of carbon, in the form of CO2 per year and account for 20-30 per cent of Earth’s total photosynthetic productivity.

There exists a diversity of different species of cyanobacteria all over the world, from temperate ponds to some of the most inhospitable environments imaginable such as the Sahara desert or Antarctic glaciers. Colonies of cyanobacteria can form filaments, sheets or even hollow balls. On a global scale, the amount of solar energy that is harvested by cyanobacteria exceeds more than 25 times the energy consumed by humans.

Cyanobacteria utilize the energy of sunlight to drive photosynthesis, a process where the energy of light is used to split water molecules into oxygen, protons and electrons. While most of the high—energy electrons derived from water are utilized by the cyanobacterial cells for their own needs, scientists at the University of Maryland BioMET laboratories found that a fraction of these electrons are donated to the external environment. To harvest those electrons from cyanobacteria, the scientists developed a photosynthetic microbial fuel cell, or PMFC, that serves as both a growth chamber for cyanobacteria and an electron harvester.

Inside the transparent PMFC, the cyanobacteria grow in direct contact with a conductive surface, called the anode. When exposed to light cyanobacteria were found to produce an electrical current, where the electrons are moving directly from the cyanobacteria to the anode.

“This study expands our knowledge about possible mechanisms for harnessing solar energy. In the future, the newly discovered physiological activity of cyanobacteria could be utilized for generating green electricity in a fully self-sustainable, CO2-free manner in the absence of any additional organic material,” says Baskakov.

The study has been published in the May 25 issue of the journal PLoS One.