By Kitty Bu and Maxim Duncan

Plastic bags, the scourge of the environment, are flying high in Beijing, thanks to a retired engineer who is turning the waste into colorful kites.

Kites are believed to have been invented in China more than 2,000 years ago, where they were traditionally made from readily available materials such as rice paper, silk and plant fibres.

The modern version also uses a ubiquitous material which 71-year-old Han Fushan said was the easiest, and cheapest, thing he could find to make kites.

"Kites are my one and only treasure," Han, who spent most of his life creating architectural drawings before retiring some nine years ago, told Reuters.

"It's through kites that I have got to know so many people and make so many friends."

Han's plastic kites have made him into something of a local celebrity, and he is very proud of his cheap and environmentally friendly creations, which cost less than 15 U.S. cents ($0.21) to make.

After years of showing up at the same park at the same time each day to fly kites, Han has developed a solid fan base among other enthusiasts.

On average, one kite takes about two days of cutting, pasting and stringing to create, and many feature wildlife, sports stars and even Beijing Opera figures.

"Plastic bags have bright colours and a good texture.

Thicker bags are good for making kites for strong winds, while thinner ones are better for light winds," Han said.

Han owns more than 600 kites and said he wants to have something new every week to entertain his fans.

"I think this is a really good idea not only for our country but also for the world. To use trash for something else is good for the environment," said Yan Juning, who often helps Han launch kites after her morning jog.

According to the state-owned Xinhua news agency, China throws away 300 tonnes of plastic bags a day, and the government has banned the use of the super-thin plastic bags which cause the most damage when buried in the soil.