Born in rural eastern Rwanda, Mr. Uwayesu was only 3 when his parents, both illiterate farmers, died in a politically driven slaughter that killed some 800,000 people in 100 days. Red Cross workers rescued him with a brother and two sisters — four other children survived elsewhere — and cared for them until 1998, when the growing tide of parentless children forced workers to return them to their village.

They arrived as a drought, and then famine, began to grip their home province. “I was malnourished,” Mr. Uwayesu said. “My brother would tell me, ‘I’m going out to look for food,’ and then he would come back without it. There were times we did not cook the whole day.”

In 2000, young Justus and his brother walked to Kigali, Rwanda’s capital and a city of about one million, in search of food and help. Instead, they wound up at Ruviri, a sprawling garbage dump on the city’s outskirts that was home to hundreds of orphans and herds of pigs.

Justus found a home with two other children in an abandoned car, its smashed-out windows and floor covered with cardboard. For the next year and a half, he said, all but the search for food and shelter fell by the wayside. “There was no shower, no bathing at all,” he said. “The only thing was to keep something warm for the night, something really warm.”

He learned to spot trucks from hotels and bakeries that carried the tastiest castoffs, and to leap atop them to grab his share before they discharged their loads to less nimble orphans.

For days when there was nothing to eat — no trucks came on Sundays, and bigger children claimed most edible garbage — he hoarded food in discarded cooking-oil tins, sunk into trash-fire embers to keep their contents warm.

Mr. Uwayesu said he was hobbled in a fall from one moving trash truck, and once nearly buried alive by a bulldozer pushing mounds of garbage into a pit.