September 20, 2011 — Hydrogen, a potential clean energy source, can be sustainably generated using just seawater, river water and bacteria, according to new research.
Hydrogen is a potentially valuable energy source but production costs and environmental concerns about using fossil fuels to produce the gas have limited its application so far.
Previous studies have shown hydrogen gas can be produced by harnessing the by-products of microbial organic matter metabolism in a device called a microbial electrolysis cell.
But the process requires an additional input of electricity to make it work effectively.
According to a study published online in the Proceedings of the National Academy of Sciences, hydrogen can be produced in a single device by integrating a water-based power supply into the system.
Exoelectrogenic bacteria are found in ponds, streams, sediments and soils, as well as in wastewater. Because they metabolize organic matter, they can transfer electrical energy to conductive materials such as metal or graphite.
Scientists designed a microbial reverse electrodialysis system, containing five pairs of seawater and river water cells separated by thin membranes, which were sandwiched between an anode containing the bacteria, and a cathode.
The passage of salt through the membranes down the gradient of seawater to river water generated the additional electricity needed to produce hydrogen without the need for fossil fuels, sunlight or wind.
Because the bacteria in the device can be fed organic waste, the system may also prove useful for wastewater treatment.