Demirbas summarize combustion properties of biofuels of different origin, in particular the content in molecules and chemical elements. The focus here is on carbon and it is estimated that between 42 and 54% of the total weight of biofuels is carbon. We use a value of 50% because Swedish government agencies use this as well. That means that 1 kg of biofuel contains roughly 500 g of carbon, which, when combusted gives rise to 1.83 kg of CO2. Read the whole article in Progress in Energy and Combustion Science.