If you wonder what might power fuel cells for personal use, think cow manure. Researchers at Ohio State University have been running fuel cells using this ubiquitous farm waste. They generate enough electricity to keep rechargeable AA batteries up and running.The experiment exemplifies the outside-the-box thinking of engineers who are determined to develop fuel cells - which generate electricity from a chemical reaction - for practical everyday uses.
Some of their research explores better ways to produce and use hydrogen, the fuel of choice for many fuel cells used today, But hydrogen is difficult to use since it must be stored under high pressure at low temperatures. It also takes a lot of fossil fuel to produce it. Other research aims to develop different types of fuel.
That's where cow manure comes in.
Various laboratories are studying the potential of certain microbes to run fuel cells using such raw material as sewage. The Ohio State team takes its inspiration from one of nature's most efficient microbial processing systems - the main stomach of a cow. Microbes in a cow's rumen fluid release electrons as they break down cellulose in the cow's feed. The team has used this fermenting fluid as the source of electrons for a fuel cell's electric current. This is the first time a microbial fuel cell has used cellulose as its energy source, according to the Ohio State announcement.
Discussing this research at a recent American Chemical Society meeting in Washington, Hamid Rismani-Yazdi, lead author of the study, explained that cow dung would be the readily available fuel of choice. It has the same microbes as the rumen fluid and enough residual cellulose for them to feed on. Mr. Rismani-Yazdi and co-author Ann Christy, along with a number of students, have been running dung-based fuel cells that, individually, produce 300 to 400 millivolts. Professor Christy says that by linking a few of these cells, the students "were able to fuel their rechargeable batteries over and over."
Meanwhile, at Purdue University, Engeny Shafirovich and colleagues are experimenting with a process that could be used in hydrogen-generating pellets contained in credit-card size containers. The hydrogen would run tiny fuel cells that, in turn, could keep batteries charged in laptop computers, cellphones, and other personal electronic devices. The pellets would contain a mix of microscopic aluminum particles and sodium borohydride. These act as a catalyst to split water into hydrogen and oxygen.
Dr. Shafirovich told the Washington meeting that using chemical mixtures like this one to generate hydrogen would eliminate the problems in handling that fuel.
Mahdi Abu-Omar, also at Purdue, is exploring another way to eliminate those problems. His laboratory is producing hydrogen with water and a group of organic molecules called organosilanes, using the rare element rhenium as a catalyst. He says that "the big point here is that hydrogen can be produced from water and a form of organic matter." He adds, "perhaps we can find other catalysts that can generate hydrogen from garbage."
As for cow dung, Rismani-Yazdi says, "The hope is that one day livestock farmers could use their farm's livestock waste lagoon as a huge fuel cell and generate enough power for their operation."