One man's trash is another man's treasure, they say. Well, in a South Korean school, one man's poo is another man's pennies.

The invention of a toilet that composts human excrement and turns it into methane biogas for use in the school's energy system has the students there re-evaluating waste like never before, as the amount of waste they contribute to the electric bills is returned to them in the form of a digital currency.

The dirty mind behind the brilliant invention was Cho Jae-weon, an urban and environmental engineering professor at the Ulsan National Institute of Science and Technology (UNIST), who insists that humanity can solve all kinds of problems if we think "outside the box."

Known as the BeeVi toilet, a condensed form of "bee" and "vision," the compost/currency commode uses a powerful vacuum to pull feces down into a composting tank, thereby eliminating all water usage.