The car uses a 1.4-litre TFSI engine with 110hp and can run on either natural gas, e-gas generated by Audi or gasoline. In pure e-gas mode the g-tron is entirely CO2-neutral.

Audi e-gas is a synthetic methane that is produced at the Audi e-gas facility located in Werlte in Lower Saxony, Germany, and the brand says the A3 Sportback g-tron fuelled by Audi e-gas is currently the most environmentally friendly form of long-distance mobility due to the process for generating Audi e-gas using green electricity which binds as much CO2 as is released when the Audi A3 g-tron is driven in gas mode.

On average the Audi A3 g-tron consumes between 3.2 and 3.3 kilograms of gas per 100km. The brand adds that fuel costs at present start at around €3.50 per 100km.

The buying principle for Audi e-gas is in line with how green electricity is distributed: Audi records the quantities of gas that the customer pays for using their Audi e-gas fuel card and ensures that exactly this amount of Audi e-gas is fed into the German natural gas network.

Customers can buy an Audi e-gas fuel card for a flat price of €14.95 per month. In addition, the costs for the quantities of gas refuelled by each customer are deducted via the Audi e-gas fuel card. The card can be used to purchase Audi e-gas at over 650 fuel stations in Germany.

Prof Dr Ulrich Hackenberg, board member for technical development at Audi AG, said: ‘In addition to our e-mobility developments, the Audi e-gas project is an important pillar of our sustainability strategy – as is the development of other synthetic fuels.’

Audi is already operating a research facility for the production of Audi e-ethanol and e-diesel with its partner Joule in Hobbs, New Mexico, and is also conducting research into the synthetic manufacture of Audi e-gasoline in cooperation with Global Bioenergies.

The carmaker added that due to the lack of infrastructure required to fully implement natural gas filling stations, there are no plans for it to introduce this model in the UK.