TAUNTON — A new gasification facility, meant to deal with the region's sludge, has been proposed to built on the site of Taunton's defunct landfill. It would be owned and run by Aries Clean Technologies — a Tennessee-based company whose facilities, one in Tennessee and one soon-to-open in New Jersey, take sewage sludge from municipal wastewater treatment plants and turn it into biochar through a gasification process. Aries's plan boasts financial boons for the city, especially after the closure of the landfill on East Britannia Street last year. But the city has received a letter of opposition from a conservation advocacy group about the potential environmental and health impacts, giving some in city government pause.