Valorsul, SA, is responsible for the management of waste produced in 5 municipalities in the area of Lisbon. Due to the high density production, a multi-municipal waste management was implemented in which the primary unit is an incineration plant, built in 1999, that produces almost 2% of the national energy demand. This paper describes the main characteristics of this plant, in particular the treatment of gases and waste management. Apart from that, and because of environmental concern of this type of unit, the monitoring program established one year before the start of the operation is described.