(Adsorbed Natural Gas) tank at 35 bar (500 psi, the pressure of gas in natural gas pipelines) in various sponge-like materials, such as activated carbon and metal-organic frameworks (MOFs). The fuel is stored at similar or greater energy density than CNG. This means that vehicles can be refuelled from the natural gas network without extra gas compression, and the fuel tanks can be slimmed down and made of lighter, less strong materials. Conversion kits Conversion kits for gasoline or diesel to LNG/CNG are available in many countries, along with the labor to install them. However, the range of prices and quality of conversion vary enormously. Recently, regulations involving certification of installations in the USA have been loosened to include certified private companies, those same kit installations for CNG have fallen to the $6,000+ range (depending on the type of vehicle). Implementation Overview Natural gas vehicles are popular in regions or countries where natural gas is abundant and where the government chooses to price CNG lower than gasoline. The use of natural gas began in the Po River Valley of Italy in the 1930s, followed by New Zealand in the 1980s, though its use has declined there. At the peak of New Zealand's natural gas use, 10% of the nation's cars were converted, around 110,000 vehicles. In the United States CNG powered buses are the favorite choice of several public transit agencies, with a fleet of more than 114,000 vehicles, mostly buses. India, Australia, Argentina, and Germany also have widespread use of natural gas-powered buses in their public transportation fleets. Europe Germany Germany hit the milestone of 900 CNG filling stations nationwide in December 2011. Gibgas, an independent consumer group, estimates that 21% of all CNG filling stations in the country offer a natural gas/biomethane mix to varying ratios, and 38 stations offer pure biomethane. Greece Greece uses natural gas buses for public transport in Athens. Also, the Public Gas Company (DEPA) has a network of 14 stations (as of June 2020), under brand "Fisikon", with expansion plans. Ireland Bus Éireann Introduced the first NGV on 17 July 2012. It will operate on the 216 city centre to Mount Oval, Rochestown, route until mid-August on trial being undertaken in partnership with Ervia. The Eco-city bus is made by MAN. Italy Natural gas traction is quite popular in Italy, due to the existence of a capillary distribution network for industrial use since