Unlike refined petrol and Diesel from hydrocarbons, natural gas, or even direct power from solar and wind, hydrogen fuel is not a naturally occurring substance. Hydrogen is an energy storage medium and must first be produced by consuming energy. Nominally considered a clean fuel, hydrogen is most often produced by reforming natural gas in the presence of a catalyst at high temperature. Hydrogen can also be produced in a green process, using an electrolyzer powered by renewables that splits water. All of these production processes require dedicated energy sources that ultimately make hydrogen a costly fuel.
Image 1:Shanghai Chlor-Alkali Chemical Corp (SCACC))
In addition to being directly produced, hydrogen can also be reclaimed indirectly from the waste gases of industrial chemical plants. Unlike costly methods for producing hydrogen directly, chemical plants often produce large quantities of hydrogen indirectly as a by-product of some other product chemical. Admittedly, the quality of hydrogen varies by process but even accounting for the cost of purifying the hydrogen the total cost of the molecule is, in many cases, still lower than direct production methods.