Waste vegetable oils have previously been used to fuel older diesel engines, but until now nobody succeeded to extract the hydrogen in them and to sequester the carbon dioxide with cheap and affordable technologies. Leeds University scientists have broken the ice and discovered an energy efficient method of extracting both hydrogen and carbon dioxide from otherwise disposable vegetable oils.
In the classic fashion, hydrogen is extracted from methane by steam reforming. The methane is mixed with steam in the presence of a metal catalyst and then heated to above 800 degrees Celsius to form hydrogen and carbon dioxide. The same procedure can’t be applied to vegetable oils, where the composition is more complex. Higher temperatures would be needed and the process wouldn’t be feasible anymore. Put aside the fact that the catalysts would become poisoned in a short time by residues left from the dirty oil, making the process not only expensive, but also polluting.
Dr. Valerie Dupont and her team at Leeds proposes a two-stage process. In the first step, the nickel catalyst is oxidized in the presence of air, forming nickel oxide. Oxidization is a process that also produces heat and takes the temperature from the starting 650 degrees to 850 degrees Celsius. In step two, the mixture of oil and steam reacts with the hot nickel oxide, and you get the same thing: hydrogen and carbon dioxide.
“The hydrogen starts to be made almost straight away, you don’t have to wait for all of the catalyst to be turned into pure nickel,” Dr Dupont said. “So as well as the generation of heat, this is another way that makes the process very efficient.”
The scientists used a special material that absorbs all the produced carbon dioxide and thus increases the reaction’s power and the volume of hydrogen extracted.
Dupont’s hydrogen extraction process can be up-scaled to industrial scales: “It is just as suitable for use at a filling station as at a small power plant,” Dr Dupont said. “If we could create more of our electricity locally using hydrogen-powered fuel cells, then we could cut the amount of energy lost during transmission down power lines.”
Hydrogen produced at McDonald’s or KFC or any other fast food chain could serve them to also sell hydrogen to customers while they’re taking a meal, decentralizing the source of energy in the economy, which, in my opinion, would be a good thing to happen.
