AS the mist rises from the river Nile each dawn, thousands of mules plod through the streets of Cairo, hauling rough wooden carts piled high with garbage.
Most of them are not heading for a dump or a furnace, but to Moqquetam, a slum on the eastern edge of the city that is home to 40,000 garbage pickers who earn their living by recycling Cairo's daily refuse.
Not surprisingly, Moqquetam's narrow alleyways stink. From every courtyard, a fetid stench rises to hang heavy in the air, as the garbage rots in the heat. But the zabaleen, as the garbage pickers are known, do not seem to notice, and work that elsewhere would be thought inhumanely disgusting, to them is just a job like any other.
Here are the raw mechanics of environmental responsibility, recycling taken to the limit, a virtue made of necessity, and also made to earn a profit.
Nothing, but nothing, is wasted. Every single item thrown out the day before by Cairo's 12 million residents is sorted and set aside for another use: cardboard boxes and old newspapers, plastic bottles and cups, dolls and shoes, aluminum foil and dented cooking pots, mountains of bones and bales of cloth, barrels of decomposing fruits and vegetables.
Metal items can be smelted into ingots and sold back to the factory that made the pots in the first place, a job that Ahmed Fouad has been doing since he was a boy stoking his elder brother's furnace.
"This is a good job," he says. "I've learned it, and it keeps my family alive.
"I want my children to have a better life, though, so I'm sending them to school. If they are educated, they'll get better jobs than this, but if they are not clever enough, they are welcome here," he says.
Plastic products, too, are recycled by the hundred ton in Moqquetam, ground up in simple mashing machines and sold back to plastic producers in powdered form for re-use. Paper is sold to be remilled, and bones are sold to be boiled into glue.
Organic rubbish is fed to the pigs that root around many of the homes. Over 60 percent of the garbage pickers are Coptic Christians from upper Egypt, who can keep and sell pigs that Muslims consider unclean. And anything the pigs wont eat is fed into an enormous composting machine, sitting at the bottom of a vast pit in the heart of Moqquetam.
That machine was installed by Sister Emmanuelle, a remarkable French nun who has made her life with the zabaleen for the past 20 years and done much to improve their lot.
"I wanted to share their life, give them their dignity, and show them their value," Sister Emmanuelle says.
"They are not the poorest people in Cairo - they earn as much as a government employee and spend much less, so most of them save money each month - but they are the most miserable, the most despised, and the most mocked, because they live among rubbish."
With money from friends and supporters around the world, Sister Emmanuelle has encouraged the zabaleen to replace the shacks they once lived in with solid, if simple, houses of mudbrick or concrete block, set up clinics to offer basic health care, and established schools where none existed before.
As health care has improved, there are fewer infant deaths and more of Moqquetam's children now have a chance to grow up and go to school.
After that, Sister Emmanuelle says, it is up to them.
"Some will go on to university, others will do their fathers' jobs," she says. "But they will be free to choose."