How Big Is the Fuel Problem and What Could Solve It?

Even if all efforts are made to reduce fuel use, some mobile sources will require liquid or gaseous fuels. Biofuels could be made with a lower carbon signature, but we are unlikely to have enough of them to meet all our needs in a de-carbonized energy system. A few ideas for filling this fuel gap are expensive or complex. We need to invest in a number of these if we are to decarbonize the fuel supply.