The greenest car one likely never heard of will soon be hitting Honda showrooms across the US as the Japanese automaker expands sales of its compressed natural gas-powered Civic.

Honda has been quietly winning green car awards for more than a decade as it cautiously introduced the Civic GX first to government and business fleet owners and then retail customers in a handful of test markets.

But the Civic GX enters a crowded field where new plug-in hybrid and fully electric cars – the Chevy Volt and Nissan Leaf – are grabbing headlines and zippy new compact cars offer competitive fuel economy.

Honda’s goals are relatively modest – doubling sales to around 4,000 vehicles in the first year of national sales while Nissan is hoping to hit annual US sales of 20,000 Leafs – but it still thinks the GX can compete.

The GX can drive up to 403 kilometres on a single tank and only takes a few minutes to fill at public or home fuelling stations.

The Leaf has a range of 100 to 222 kilometres depending on road conditions and takes 30 minutes to partially charge at a quick-charge station and seven to 20 hours using a standard 220 or 110 volt outlet.

GM’s Volt can drive 40 to 80 kilometres on its battery before switching over to a gasoline-powered engine and takes four to 10 hours to charge.

Honda’s GX is also the cleanest car on the US market, according to the American Council for an Energy-Efficient Economy which looks at a vehicle’s total environmental impact.

That’s because natural gas is a clean-burning fuel. It consists primarily of methane and emits about 30 per cent less carbon dioxide and 70 to 90 per cent less smog-forming particulates than gasoline.

Electric cars may emit nothing from the tailpipe, but they have a significant carbon footprint because 45 per cent of US electricity is generated by coal. Their batteries also carry a heavy environmental toll.

But it will be years before the GX or electric cars are sold in sufficient numbers to make a significant dent in greenhouse gas emissions, cautioned Lonnie Miller, an analyst at auto research firm R. L. Polk.

While owners can fuel up at home with a relatively cheap unit called “Phil,” long-range trips are essentially out of the question because there are only about 870 public fuelling stations in the entire country.

Honda was the first automaker to introduce a hydrogen fuel cell prototype in 1999 and began testing a small fleet with retail customers in 2005. It also plans to introduce a plug-in hybrid next year.