Environmental Assessment. Life cycle assessment (LCA) was used to characterize the carbon intensity (i.e., greenhouse gas emissions normalized to kg CO2 equivalents with a 100year time horizon) from materials (construction and O&M replacement), energy, and direct fugitive emissions from excreta. Environmental impacts were estimated from each system's materials and electricity consumption using the ecoinvent v3.6 database 38 and the U.S. EPA's Tool for the Reduction and Assessment of Chemicals and Other Environmental Impacts, TRACI 2.1 v1.03 .