Making Hydrogen From Waste Vegetable Oil

Tuesday, July 27 2010

Researchers at the University of Leeds have found an energy-efficient way to make hydrogen out of used vegetable oils discarded by restaurants and other establishments. The process generates some of the energy needed to make the hydrogen gas itself and is also essentially carbon-neutral.

"Hydrogen-based fuel could potentially be used to run our cars or even drive larger scale power plants, generating the electricity we need to light our buildings, run our kettles and fridges, and power our computers. But hydrogen does not occur naturally, it has to be made. With this process, we can do that in a sustainable way by recycling waste materials, such as used cooking oil," said Dr. Valerie Dupont, who is leading the project.

Hydrogen can be made from simple fossil fuels, such as natural gas. The fuel is mixed with steam in the presence of a metal catalyst then heated to above 800 degrees centigrade to form hydrogen and carbon dioxide. When much more complex fuels are used, such as waste vegetable oil, it is difficult to make very much hydrogen using this method without raising the temperature even further. The reactions could be run at lower temperatures but the catalysts would quickly become poisoned by residues left over from the dirty oil.

Dr. Dupont and colleagues have perfected a two-stage process that is essentially self-heating. To begin, the nickel catalyst is blasted with air to form nickel oxide - an exothermic process that can raise the starting temperature of 650 degrees by another 200 degrees. The fuel and steam mixture then reacts with the hot nickel oxide to make hydrogen and carbon dioxide.