The principle

How can one distinguish between fossil and biogenic CO2? Carbon atoms have a trait that has been used for decades; they can be used to determine how old something is. This method, called carbon dating, is traditionally used to determine the age of mammoths, fossils and paintings. Carbon dating distinguishes between carbon which we call C14  (biogenic carbon) and C12 (fossil carbon). Cosmic radiation creates C14 in the atmosphere. Living organisms absorb the C14. When these living organisms die, over time the C14 will turn into C12 and become fossil fuels.

These fossil and biogenic fuels are transferred back into the atmosphere when they are burned by e.g. waste-to-energy installations, cement kilns and paper mills. The biogenic and fossil carbon leaves the installation through the stack, thereby closing the carbon chain.