This chapter provides a concrete and complete example of a life cycle assessment (LCA) application. It compares alternative treatments of sewage sludge from municipal wastewater, as addressed in a detailed study (Houillon and Jolliet 2005) carried out in collaboration with a group of French and Swiss industries. Following a short introduction, this example illustrates the four phases of LCA: goal and scope definition, inventory of resource extractions and emissions, impact assessment, and interpretation. For each of these phases, the calculations will be detailed for each considered scenario. The analysis of environmental impact is calculated using two methods: IMPACT 2002+ (Jolliet et al. 2003) and Eco-indicator 99 (Goedkoop et al. 1998).