If you thought that chocolates only had the power to tantalise your taste buds, think again, as microbiologist Lynne Mackaskie and her colleagues at the University of Birmingham in the UK have powered a fuel cell by feeding sugar-loving bacteria chocolate-factory waste.
"We wanted to see if we tipped chocolate into one end, could we get electricity out at the other?" Lynne says.
The team fed escherichia coli bacteria diluted caramel and nougat waste. The bacteria consumed the sugar and produced hydrogen, which they make with the enzyme hydrogenase and organic acids.
The researchers then used this hydrogen to power a fuel cell, which generated enough electricity to drive a small fan.
The process could provide a use for chocolate waste that would otherwise end up in a landfill. What's more, the bacteria's job doesn't have to end once they have finished chomping on the sweet stuff.
Place the bacteria in a vat with hydrogen and liquid waste from spent converters, and the enzymes again get to work.
The same hydrogenase used to produce hydrogen splits the gas into its constituents, generating electrons that react with palladium ions in the solution.
This forces the palladium out of the solution, and it sticks to the bacteria. The palladium-coated bacteria can then be recycled as catalysts for other projects, Mackaskie says.