Renewable Energy at Deer Island
Massachusetts Water Resources Authority

The MWRA’s Deer Island Wastewater Treatment Plant treats an average of 365 million gallons of wastewater each day from 43 communities in greater Boston and is one of the largest electricity users in the Northeast.

 Deer Island currently self-generates 20% of its electricity needs and more than half of the Island’s energy demand is provided by on-site, renewable generation. 

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In addition to solar power, MWRA has a number of on-going and new renewable energy programs to ensure that the facility reaches the goal of 30% by 2020 established by Governor Patrick’s Executive Order 484:

• MWRA has received a “Determination of No Hazard” from the FAA for construction of two 190-foot, wind turbines (up to 660 kW) which will generate up to 2 million kW hours per year for an annual estimated savings of $106,000.
• The methane generated from the sludge digestion process (“digester gas”) is collected and used in Deer Island’s on-site power plant to create steam that supplies hot water and heat for the facility. The steam is also run through a steam turbine generator that produces electricity.  Using methane saves $15 million in annual fuel oil costs.
• Digester gas-derived electricity generated by the steam turbine qualifies as a renewable (“green”) source of energy under the Massachusetts Renewable Portfolio Standards Program. This program prescribes that a minimum amount of power that must be supplied into the Massachusetts market be derived from renewable energy sources. Deer Island is awarded certificates for each megawatt-hour produced. Suppliers that do not meet the minimum requirement through their own sources can purchase certificates from generators such as Deer Island through an open bid process, generating $1.3 million in revenues for FY2007.
• Deer Island is also able to self-generate electricity by running its own two 26-megawatt combustion turbine generators to reduce or eliminate its purchases from the power grid. Deer Island participates in the Load Response Program, administered by the not-for-profit Independent System Operators of New England (ISO-NE). In addition to the direct compensation MWRA receives from ISO-NE when Deer Island removes itself from the grid during price response events, MWRA also avoids the high market prices that typically occur during such events. Revenue from the program for FY2007 was $930,000.
• Deer Island electricity has been purchased competitively since 2001. Energy market conditions are characterized by their volatility, and MWRA has sought to balance the ability to respond to changing conditions with maintaining a measure of budgetary predictability. During FY2007, MWRA saved more than $2.6 million dollars by purchasing electricity from a competitive power supplier as compared to the price of basic service from the local utility.
• Since 2002, energy is recovered by the flow of treated wastewater as it drops from the plant into the outfall tunnel shaft through two one-megawatt hydroelectric generators that produce approximately 5 million kW hours of electricity, avoiding about $500,000 in energy costs annually.
• Through NStar, Deer Island is currently in the first phase of a four phase lighting improvement program aimed at replacing existing lamps and ballasts with high performance fluorescent reduced wattage fixtures, integrated day lighting and occupancy controls.  Also replacing “Exit” signs with LED technology.
• Electrical upgrades are planned at the two pump stations to replace the variable frequency drives that power the eighteen 1,250 horsepower motors with more energy efficient technology. Work at the South System Pump Station was completed in August 2007, resulting in an annual reduction of electricity purchases of $130,000 plus a rebate of $209,000.

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