OWASA’s Carbon Footprint Analysis and Opportunities for Industry-Wide,Efficiency-Gain Tracking

摘要

A number of initiatives have been started to encourage optimization of energy use and production of green power from renewable fuels associated with wastewater treatment.As one example,the Water Environment Research Foundation(WERF)has initiated the Optimization of Wastewater Solids Operations(OWSO)Issue Area Team and associated program managers and research contracts.OWSO has a stated goal of reducing energy use at publically owned treatment works(POTWs)by 20 percent. One of the limitations of the current state of the practice is the lack of a metric or measurement tool that evaluates how well we are performing as an industry against goals like OWSO’s 20 percent energy reduction goal.Carbon footprint analysis may be the most appropriate metric/tool;this paper summarizes how one utility,the Orange Water and Sewer Authority (OWASA)of Chapel Hill,North Carolina is accounting for its energy savings and effects using that tool.Opportunities for trading carbon emission reductions may be available and provide motivation in the form of cash for measuring the improvements using well-documented procedures.If aggregated,these savings could be tracked industry wide to provide an ongoing assessment of the advances that the wastewater industry is making. A number of markets exist for the North American exchange of green house gas(GHG)emission reductions and global warming credits.Carbon is exchanged in metric tons of carbon dioxide (CO2).The authors propose that,to the extent possible,energy efficiency gains at POTWs be documented,converted to metric tons of CO2 and sold on the carbon markets.This approach provides the following benefits:1. Documentation of individual POTW electrical and fossil fuel use reductions using a common unit of measurement. 2. Ability to track and total the overall efficiency improvements by the industry. 3. Incentive in the form of payment for carbon reductions that can also be used as public relations capital for public education on the additional steps taken by the utility for environmental enhancement. This paper summarizes OWASA’s utility-wide and plant-specific carbon footprint baselines and measured gains that resulted from carbon footprint reduction projects at their Mason Farm Wastewater Treatment Plant(WWTP).The degree of carbon improvement necessary to achieve Kyoto-defined reduction goals will also be highlighted–with special attention being paid to the ever-increasing wastewater loads and increasingly stringent effluent treatment requirements that WWTPs typically face.Both of these factors likely increase the amount of energy required to operate a POTW over time.