ABIDJAN, Ivory Coast — She left home before dawn. Her four children were still asleep in her cement block house in Abobo, a maze of shops and houses occupied by dockworkers, taxi drivers, factory laborers and street sellers.

She and a friend crossed into the upscale neighborhood of Angré, home to doctors and businessmen. They tossed the plastic castoffs of the consumer class into bags slung over their shoulders as the cocks crowed and the sun peeked over villa walls draped with bougainvillea.

Mariam Coulibaly is part of a legion of women in Abidjan who make their living picking up plastic waste on the city streets and selling it for recycling. Now they are lead players in a project that turns trash into plastic bricks to build schools across the country.

They are working with a Colombian company to convert plastic waste — a scourge of modern life — into an asset that will help women earn a decent living while cleaning up the environment and improving education.