The anerobic decomposition of organic components of wastewater produces methane and nitrous oxides.  The carbon dioxide produced from aerobic decomposition and from the incineration of sewage sludge is not included in the inventory, because the carbon is wastewater is assumed to be produced sustainably, giving a net zero emissions.  Rhode Island data on the total amount of Biological Oxygen Demand (BOD₅) produced in the state were not available, and so the Workbook default of 0.136 lbs of BOD₅ per day was used along with Rhode Island population data to estimate total BOD₅ production.  The default assumption that 15% of this material is decomposed anerobically leads to an estimate of ca. 12,000 MTCE, a 0.3% contribution from wastewater to the total greenhouse gas emissions, approximately one-third from methane and two-thirds from nitrous oxide.  The calculation appears in the Wastewater appendix.  Note that the slight reduction in emissions between 1990 and 1996 results solely from a small decrease in the state’s population in this time period.