Measuring Methane-Based Digester Gas Flow In Wastewater Treatment Plants

As a greenhouse gas, methane remains in the atmosphere for approximately 9 to 15 years according to the various U.S. and global government sources. Methane is over 20 times more effective in trapping heat in the atmosphere than carbon dioxide (CO₂) over a 100-year period and is emitted from a variety of natural and human-influenced sources. Beyond wastewater treatment facilities, other anthropomorphic sources of methane include landfills, natural gas and petroleum systems, agricultural activities, coal mining, stationary and mobile combustion and a variety of other industrial processes.

Methane digester gas is the primary component of natural gas, and is also an important energy source in the U.S and around the world. While traditionally flared by wastewater treatment plants (WWTPs), many facilities are now turning the methane produced by their digester processes into a fuel source. The harvested digester gas is used to generate on-site heat, fuel boilers and, with co-generation technologies to generate electricity.

In large WWTPs, cleaned gas and electrical energy produced by the co-generation technologies is frequently connected into the public power grid, creating an income stream resulting in an even better ROI and payback for the WWTP operator. In addition to the obvious cost savings and economic benefits, the WWTP plant gets ahead of the greenhouse gas regulations curve as well as reaps the strategic benefits of being environmentally and tax rate attentive with their local community. Properly measuring, treating and utilizing a historical by-product gas as an energy resource provides a win-win solution for the WWTP and the entire community of stakeholders.