A new study from the US says methane emissions from natural gas flaring have been vastly underestimated. 

Flaring - the burning of unwanted natural gas from oil and gas wells - releases five times more methane into the atmosphere over the United States than previously assumed, according to the study.

Methane is a potent greenhouse gas, and the study finds that the warming potential between the stated and actual effectiveness of flaring across the United States is equivalent to putting 2.9 million more cars onto the road each year.

A research team carried out airborne sampling over areas that together account for 80 per cent of US flaring.

The fossil fuel industry and US government have been working on the assumption that flares remain lit and destroy methane with 98 per cent efficiency.

According to the study, a combination of unlit flares and some flares that were burning highly inefficiently meant that on average, flares destroyed just 91.1 per cent of methane.

That implies methane emissions from flaring are five times as high as currently officially reported.

The team found that most flares actually operate at 98 per cent efficiency, but a modest number of malfunctioning flares operate at efficiency as low as 60 per cent, and 3-5 percent of flares are unlit - directly venting unburned gas into the atmosphere.

Other estimates suggest that the amount of gas that is currently flared each year - about 144 billion cubic metres - could power the whole of sub-Saharan Africa.

The research team has put forth a number of solutions to improve the practice, including reducing the total volume of flaring activity, increasing flare efficiency, and reducing the number of unlit flares.