The Blending Time — Michael Kinch

Congratulations on turning age seventeen. You are now ready for placement by the Council government.
For kids in the year 2054, turning seventeen means they're ripe for Global Alliance work assignments that range from backbreaking drudgery to deadly canal labor. Trying to survive in a desiccated world that's been ravaged by plagues, AIDS III, and environmental disasters, three "s'teeners" from very different backgrounds think they've gotten lucky. Jaym, Reya, and D'Shay are chosen to be among thousands of blenders whose task is to help repopulate Africa after a solar flare left its people sterile.
But the continent itself -- roiling with civil war and mercenaries intent on crushing the blending program at any cost -- poses the gravest danger of all. Separated, the three friends struggle to escape horrific situations, somehow reunite, and reach a camp in the mountains that promises salvation from the harsh and threatening world.