Killing Two Burdens with One Self-Sufficient Device

By: Pooja Ravindran, GreenBlogger

We all can elaborate in heavy detail that one dream job that we wish we could pursue, but know will not happen in this mortal life. For me, folks, it would be being paid lots of money to go around the world and talk to the scientists and researchers that are bringing my dream- sustainable global development and progress- to reality, and share it with the world. Essentially, being a Carolina Scientific blogger but with the money and traveling and perks of the job. Well, we can’t always get what we want (thanks, Rolling Stones) which is why I want to simulate my contributions to this blog on this idealistic model and give you a taste of the sustainability-related goings-on in the lab and the field. Today’s topic is fuel from waste- without the bad byproducts.

In developing the self-biased solar-microbial device, Yat Li and his team at University of California at Santa Cruz have eliminated the need for conventional electricity to overcome the external bias used in electrolysis of water using a combination of microbial fuels cell (MFC) and photoelectrochemical cell (PEC) technology.

The new hybrid solar-microbial device is self-driven and self-sustained, because the combined energy from the organic matter (harvested by the MFC) and sunlight (captured by the PEC) is sufficient to drive electrolysis of water. Photo credit University of California - Santa Cruz.

For all you jargon aficionados, let me break it down in some detail: In this configuration, the PEC (very similar to photo-voltaic cells) consists of a titanium dioxide photoanode and platinum electrode. When illuminated by sunlight, the holes in the anode oxidize the water in the electrolyte to oxygen with a hydrogen-ion by product, and supply electrons to the MFC. The MFC is two-chambered with anode- plain carbon cloth- and cathode- platinum-loaded carbon cloth- separated by a cation exchange membrane. On the anode side, organic matter is oxidized by bacteria to produce hydrogen and electrons. On the cathode side, the electrons from the PEC and hydrogen from the anode side of the MFC are used to produce water. The electrons produced by the bacteria are supplied to the platinum electrode in the PEC to drive hydrogen-gas production from the hydrogen-ions in the electrolyte.

This is a schematic diagram of the PEC-MFC self-driven solar microbial device. 

Long story short, with a consistent supply of sunlight, wastewater and these handy electrogenic bacteria, hydrogen gas can be produced. And through this process, you even clean the wastewater! The heart of the application of the PEC-MFC device, as mentioned earlier, is the electron-generating capacity of the unusual, electrogenic bacteria which essentially removes the jump-start electric power component- removing cost and harmful by-products- to begin the electrolysis process. This self-sustaining and self-driven process, if capable on a commercial scale, could be integrated with existing wastewater infrastructure in areas of adequate insolation and transform water treatment and energy production methods.