Today hydrogen has very limited use as an energy carrier in the UK. The hydrogen supply chain that does exist is almost exclusively for the chemical industry, with the hydrogen predominantly transported by vehicle in liquid or compressed form. The pipelines that do exist are used to move hydrogen relatively short distances and at relatively low volumes within the confines of chemical plants. Hydrogen is stored in reasonably large quantities in salt caverns, helping to balance somewhat intermittent consumption with the much steadier output from production plants. At present, hydrogen is predominantly produced from natural gas using a process known as steam methane reforming (SMR) but can be produced in a number of ways and from a variety of sources.