It is an apocalyptic scene. Fires burn amid the detritus on the side of a major road, sending acrid smoke into the air. Thin men in filthy clothes move amid the rubbish. Some recline on old sofas, watching as trucks lurch past, spewing diesel fumes just feet away. Women and children emerge and disappear down a passage of corrugated iron leading to slum houses illuminated by light bulbs that are linked, illegally, to a mains supply by overhead wires.

Welcome to Enterprise Road, Nairobi’s recycling centre.

A closer look reveals the careful organisation of the place. Beside the gateway to the slum housing is a mountain of large, dirty white bags containing plastics and cardboard. Next come wooden pallets that once held vegetables. Further along is a stack of airline trolleys, their metal bars in tidy parallel. Plastics, cardboard, wood and metal. Each is a separate business.

The fires burn paint off metal. They also incinerate the foam and fabric cushioning of chairs that once spun in city offices. The smell is bad and the fumes attack the lungs.

“You get used to it and then you don’t smell it any more,” says Sixtus Nyamai, who runs a metal recycling business called Baba Kilatya on the edge of the dual carriageway. He is the local chief, chairman of an area of roadside called Barclays Village, after the bank that stands at the junction. If officials want to know about anybody or anything going on, they come to him, he says.

Nyamai hires trucks and labourers to collect unwanted metal objects from businesses, shops and factories all over Nairobi. A lumbering lorry pulls over; the back drops down. Three men clamber aboard. They throw out used car batteries, which hit the muddy ground with a thud.

Nyamai used to live in the slum. That was 10 years ago, when he started the business. Now he lives with his wife, who works alongside him, in a house near the airport. Recycling pays. He has put his children through school. He buys steel for 25 shillings (18p) and resells it for 30 shillings to a factory that melts it down, by the Athi river.

Ordinary aluminium costs 100 shillings and resells for 120. Hard aluminium fetches a lower price: he buys it for 70 shillings and sells for 90.

Sometimes individuals turn up on a treasure hunt. Nyamai cradles a car wing mirror, in perfect condition though with no box. It could be useful to somebody.

The slum is a testimony to human ingenuity. One of the patchwork coloured shacks of corrugated iron has an upper storey that projects over the path, like a Tudor house. Beside it is a long white pipe that allows waste water to spill out and down the slope, clear of the home.

By the slum entrance is a man leaning over the wooden fence that separates his living quarters from the mud footpath and the main road. He is old, but lean and strong. His earlobes have large holes that speak of his former life. Ole Kalau is a Maasai, far from the cattle pastures of southern Kenya.

There is a not a leaf of greenery on Enterprise Road and the breeze carries only fumes. But there is work for him as a security guard. He may not be leaning on his spear, but nobody will mess with a Maasai.