Hydrogen is a zero carbon fuel at point of use. When generated from renewable sources, or when combined with carbon capture and storage, it is 100% carbon free; from other sources it helps to improve energy efficiency and grid balancing. For transport applications hydrogen can be used in a fuel cell to generate electricity directly on board the vehicle, or in a conventional combustion engine, replacing hydrocarbons such as diesel, petrol or methane gas.
If hydrogen is used in combustion engines, particulates and other emissions that impact on air quality are also dramatically reduced, although the by-products of the reaction with nitrogen in air (NOx etc), have to be managed carefully. Traditionally the latter, management of NOx etc, has meant that it is extremely challenging to ensure that ultra-low emissions standards (the combination of low carbon and improved air quality emissions) can be met by hydrogen combustion approaches.
If the hydrogen is used in an on board fuel cell, the owner has an electric vehicle that can be refuelled in less than 5 mins, addressing range anxiety and then providing all the other benefits that electric mobility can provide.