Trash piled nine yards high is converted to heat and electricity at a waste-to-energy incinerator in Oslo.Credit...Brian Cliff Olguin for The New York Times OSLO — This is a city that imports garbage. Some comes from England, some from Ireland. Some is from neighboring Sweden. It even has designs on the American market. “I’d like to take some from the United States,” said Pal Mikkelsen, in his off