Hydrogen is the smallest molecule with low energy density: three times less energy per M3 than natural gas.
Hydrogen can be transported perfectly well through gas pipelines and, with limited modifications, also through existing natural gas pipelines. This is not always an option. Storage or transport in a ship or by truck requires other solutions. Otherwise, a truck carrying hydrogen would transport a lot of gas with hardly any energy.
Transporting hydrogen under pressure
Hydrogen can be compressed with enormous pressure. Typical of gaseous storage are the typical composite high-pressure vessels (200, 350 or 700 bar). The disadvantage is that 6% energy is lost through compression by using a compressor.
Transport of liquid hydrogen
At a temperature of -252.87°C, hydrogen is liquid at atmospheric pressure. It is then eight hundred times less voluminous per unit weight. Hydrogen can then be stored in very well-insulated tanks, also called “dewars” (named after Sir James Dewar). Liquid hydrogen is interesting for storage and transport, but cooling obviously takes a lot of energy.
Transport of hydrogen by converting it into a different chemical compound
Another option is to convert hydrogen into another molecular compound, such as ammonia (NH3) or formic acid (CH2O2). These are heavier molecules with more hydrogen per volume. Then transport is easier. Mentioned compounds are liquid at atmospheric pressure. However, it takes energy to extract the hydrogen from the compounds.