Des Moines Water Works recently reported its greenhouse gas (GHGs) emissions to The Climate Registry, a nonprofit organization that is a collaboration of North American states, provinces, territories, and Native Sovereign Nations. The purpose of the organization is to set consistent and transparent standards to calculate, verify and publicly report GHG emissions. Reports for CY 2007 though 2009 can be viewed through the Climate Registry Web site: www.theclimateregistry.org.
DMWW analyzed and reported its GHG emissions to gather information regarding sustainability of treatment and distribution processes, as well as contribution of GHGs to the environment. The analyses did provide a few surprises. Electrical power usage contributes over 90% of total energy use and GHG emissions. Clearly the greatest opportunity to diminish GHG emissions is to reduce electrical demand and improve energy efficiencies. Most of the electricity is used to pump large volumes of water where distance and elevation are the primary variables to energy requirements. Location of facilities as well as design is an important factor in overall efficiency. The two lime softening treatment plants (Fleur Drive and L.D. McMullen at Maffitt Reservoir) were very similar in their GHG emissions per million gallons of treated water, even though the newer McMullen facility is a more efficient design with newer and better equipment. This analysis provides a baseline to compare energy efficiencies of differing technologies, such as the all-membrane treatment process at the new Saylorville Water Treatment Plant versus lime softening at the Fleur Drive and L.D. McMullen plants.
Documenting GHG emissions according to rigorous reporting protocols provided invaluable information on power use and inefficiencies, and identified opportunities to improve energy efficiency. The process identified potential capital investments that will reduce the utility’s risk to a limited energy supply, so DMWW can continue to provide a sustainable supply of water to customers in a cost effective and environmentally responsible manner.