MINA (Saudi Arabia) • Thousands of cleaners are busy separating plastic from other rubbish as more than two million Muslims wrap up a pilgrimage to Mecca this week that presents a huge environmental challenge for Saudi Arabia.

The Mamuniya camp in Mina near the holy city is dotted with colour-coded barrels - black for organic waste and blue for cans and plastics for recycling.

It is all part of an initiative to reduce the environmental footprint of the haj, one of the world's largest annual gatherings.

More than 42,000 tonnes of waste are produced during the annual pilgrimage to Islam's holiest sites, according to Mr Mohammed al-Saati, head of sanitation for the Mecca municipality.

"We're facing some real challenges, primarily the sheer volume of waste produced... along with the number of pilgrims, the limited space around the holy sites, different nationalities and the weather," he said.

"Pilgrims can be friends of the environment. It starts by raising awareness back home."

The haj, which started on Sunday and ends today, drew nearly 2.4 million Muslims from around the world this year, according to official Saudi figures.

More than 13,000 sanitation workers and supervisors have been hired for this year's pilgrimage season, which saw temperatures rise to 44 deg C this week.

A handful of camps in the town of Mina, the site of the symbolic stoning of the devil ritual during the haj, have begun to implement plans to turn "green", cutting back on waste and encouraging pilgrims to do their part.

Banners hanging near the Kaaba, a black structure inside Mecca's Grand Mosque towards which Muslims around the world pray, also feature the recycle logo this year.

The authorities aim to cut waste volumes by two-thirds by 2030, Mr Saati said, with a plan that speaks to both environmental ethics and religious belief.

Sorted waste collected from the pilgrimage sites will be sold to companies that handle recycling.

All proceeds will be given to charity, in line with the Muslim belief in "sadaqah", or voluntary donations.

Workers in bright green vests make their way across the streets and alleys, picking up soda cans and plastic water bottles as pilgrims pack their things to return home.

Signs encouraging pilgrims to sort their waste can be seen across the Mamuniya camp - along with signs reading "Sadaqah, not litter".

"The idea of an environmentally friendly camp is really important to us, to preserve the sanctity of the site," said Mr Hatem Mumena, the camp's general manager.

But he admits there is still a long way to go, as the numbers of pilgrims attending haj is expected to rise. Saudi Arabia hopes to welcome some 30 million pilgrims per year by 2030. "This is just the beginning," he said.

AGENCE FRANCE-PRESSE