The growing popularity of hot air ballooning has raised questions about the environmental impact of the sport.

Hot air balloons use natural gas to heat the air that lifts them and a typical hour-long flight can consume up to 100 litres - that's enough to drive a car for more than 1,000 kilometers.

The world's largest manufacturer, Spain-based Ultramagic Balloons, says it has tackled the problem by developing a two-layered, more efficient eco-friendly design.

The company's eco-balloons use a specially-developed silver fabric on the outside and include a lightweight insulation layer.

"The main benefit is the fuel saving," said Jordi Diaz Casaubon, an aeronautical engineer at Ultramagic.

"You can save up to about 50%, so this gives you two options: fly cheaper or you can have more capacity [to fly further] in a single flight."

Ultramagic worked with German company Festo to test and develop the special insulated fabric used in the new balloons.

In a controlled test, a balloon made from the new fabric consumed less than a third the gas of a normal hot air balloon.

Although it makes the balloon more expensive - around $100,000 - the company said the insulation layer makes them stronger and longer-lasting.

"Each batch of fabric that we receive we do a stress test, just to check," said Neus Llado Gambin, an engineer at Ultramagic.

"In theory our supplier already checks it that it is good, but we also check before we send it to the customer."

The company has also been working on technology to make the sport safer, developing a smartphone app to track and log flights in real time and a monitor that alerts a pilot if the balloon comes too close to power lines.

Only a few of the 200 balloons Ultramagic makes each year are made with the new fabric, but the company hopes its environmental credentials will help make it more attractive to both hobbyists and those running professional ballooning trips.

Source: Al Jazeera