On average, a healthy human generates 1.4 liters (0.37 gallons) of urine per day. Dr. Gabriel Luna Sandoval, an engineering researcher at the State University of Sonora (UES), experimented with using urine in a cell normally used to extract hydrogen from water. After several adjustments, he was able to produce biofuel for powering domestic stoves and generating electricity.
According to Sandoval, five milliliters of urine yields one liter of bio-gas, so a family of three people can produce the hydrogen necessary to use as fuel for a week.
To obtain hydrogen, the device uses an electrochemical electrolysis process in which the 20-square-cm cell passes 12-volt photovoltaic energy, which is then stored in a battery. Urine yields one molecule of urea and one molecule of water, from which are released two molecules of oxygen and six of hydrogen to serve as fuel.
"At first it was not easy because in electrolysis, urine does not behave like water because it contains salts and organic solids that adhere to the electrodes of the cell and make it difficult to carry out the process,” said Sandoval. “Urine is a natural electrolyte, has organic compounds, and therein lies the difference.”
After testing various configurations of cells, Sandoval was able to generate hydrogen from urine, a patent for which was issued in March of this year.
The next step is to develop a practical, portable cell, ideally the size of a small suitcase so it can be carried and easily adapted to different needs at home. Sandoval reports that the research team he heads in the UES is working on a prototype for fueling a car, but that will take longer. "We have under construction a cell not with stainless steel electrodes but with a more expensive material, which requires further tests", he said.
For more energy news, read about improving the life and performance of fuel cell electrodes.