Hydrogen is a component of water, so we must separate it from water using electrolysis. This is a well understood technology, using the passage of an electric current through specially treated water. For example, it has been done on a large scale in Norway for the past 90 years, using that country’s vast hydroelectric power to split water, thus gaining the hydrogen as a saleable product (it is used in the metal and food industries). A similar use of renewably generated electricity could furnish us with all the hydrogen we need to displace all the fossil fuels which now use – about 12 billion tonnes a year.