MMSD's Renewable Energy with Methane Gas

We have all seen our energy bills going up.  The Milwaukee Metropolitan Sewerage District (MMSD) faces this as well and has several projects to reduce these costs to our ratepayers.  One such project is the upgrade to the mixing units in our digesters.

At the South Shore Water Reclamation Facility, MMSD has large tanks that digest the biosolids that are generated by the wastewater treatment process.  Inside these digester tanks are mixing units that move the biosolids around to ensure good mixing and better energy production. 

Above: Aerial view of the South Shore Water Reclamation Facility in Oak Creek, WI.

As these biosolids are distributed through the digesters, they are digested, reducing the volume of the biosolids that need to be handled, and methane gas is produced.  This gas is collected, cleaned, and then burned in generators to create electricity.  If the gas was not used to generate electricity, it would have been flared off, a waste of a huge source of energy.  Originally installed in the mid-1960s, the digester mixing units needed repairs.

Over the last five years, MMSD has been upgrading the mixing units with newer systems.  The new mixing units also increased the production of methane gas.  This increased gas production is creating heat and power that is currently being used to power the wastewater treatment facility. 

Approximately 58% of the energy needed to power the South Shore facility in January 2022 has been generated by methane gas from the digesters.  

MMSD Renewable Energy Usage

MMSD’s renewable energy usage, for the last 365 days, at both water reclamation facilities.

This reduces the need to buy electricity and natural gas from the local power grid and translates to approximately $140,000 in savings to the ratepayers in one month. This project is one of nineteen energy efficiency and renewable energy projects in MMSD’s Energy Plan, which aligns our 2035 vision:100 percent of our energy needs with renewable energy sources.

Cleaner energy that saves all of us money – that’s the ticket!

Kevin L. Shafer, P.E.
Executive Director - Milwaukee Metropolitan Sewerage District 

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Additional MMSD Sustainability Efforts