Charlotte Observer: The novelty of power plants that burn chicken droppings, mandated by North Carolina’s new renewable-energy law, has given way to irony: They might be dirtier than the coal plants that environmentalists loathe. A Pennsylvania company, Fibrowatt LLC, plans to build plants powered by poultry litter, the birds’ bedding material, in Montgomery, Surry and Sampson counties. Fibrowatt says the plants will give growers a new market for the tons of waste produced in one of the nation’s biggest …