Carbon Neutral? Audi A3 g-tron

When we talk about environmental vehicles and emobility it's always electric, hybrid and hydrogen powered cars that spring to mind first. Audi, however, are on the verge of releasing a fully sustainable natural gas-powered A3 onto the roads.

What is it?

The g-tron is essentially an Audi A3 Sportback powered by natural gas as well as petrol. The headline figures are carbon dioxide emissions of 30g/km in gas-mode and a combined range of over 800 miles. That sort of range is impressive, but comparable to today's clean diesels. Using natural gas alone the g-tron is capable of just under 250 miles, with petrol making up the remaining 500-or-so miles. When running on petrol, carbon dioxide emissions increase to 95g/km, which whilst no means an embarrassment is some way off the natural gas equivalent.

Using an engine based on the new 1.4-litre TFSI petrol engine – featuring modifications to the cylinder heads, turbocharger, fuel injection system and catalytic converter – the g-tron develops 110bhp and a respectable 200Nm of torque. Top speed is 118mph and 60mph comes up in 11 seconds, making it similar to lower specced variants of Volkswagen's Golf.

Natural gas-powered machines are nothing new, but when the g-tron is running on Audi e-gas – to be produced at a plant in Werlte in Germany – then “no more CO2 is released than was chemically input in its production beforehand”. This means that for a potential of 250 miles, the A3 g-tron can operate on a closed loop. In other words it's carbon neutral (well, almost, because firing up the engine requires a tiny bit of petrol).

How does it work?

Technically a hybrid, then, the A3 g-tron uses both compressed natural gas (CNG) and conventional petrol. The gas, and how it's produced, is what makes this project of interest.

The CNG is stored in two tanks underneath the luggage compartment, each holding seven kilos at 220 bar pressure. The tanks are forged of carbon-fibre reinforced polymer and fibre-glass, giving them both strength and less mass than conventional tanks.

The gas itself is the product of Audi's e-gas project, which aims to develop a chain of sustainable energy carriers, starting by producing electricity from renewable energy sources and ending with gas-powered cars. The plant at Werlte - which will produce synthetic methane (e-gas) from carbon dioxide and this renewable electricity – is almost complete. The carbon dioxide used at the start of the process is taken from a nearby biogas plant, and would otherwise be released into the atmosphere.

E-gas produced at the Werlte plant alone with be enough to power 1,500 A3 g-tron vehicles from over 9,000 miles each year.

Can I have one?

It's difficult to get concrete details on a car that doesn’t really exist yet, but Audi hope to have A3 Sportback g-tron vehicles on the road by the end of the year. Although Audi is promoting its own e-gas, the g-tron will also be capable of running on conventional natural gas.

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