The researchers have run a handheld calculator on a prototype sugar battery the size of a postage stamp, running the battery on sap, flat soft drink and sweetened drinks.

"This study shows that renewable fuels can be directly employed in batteries at room temperature to lead to more energy-efficient battery technology than metal-based approaches," says study leader Shelley Minteer, Ph.D., an electrochemist at Saint Louis University.

The process combines sugar with air, generating electricity and water as the main byproducts. Materials used to build the batteries are biodegradable.

So far the researchers have run the batteries on sap from trees and cacti, flat soda and sweetened drink mixes. While it's not the first fuel cell batteries to run on sugar, Minteer claims that this is the longest-lasting and most powerful of its type to date.{moscomment}