Digester Gas
The most popular digester gas technology converts wastewater treatment gas to electricity, employing internal–combustion engines that run a generator to produce the electricity. This electricity is used to power internal operations, while the excess is sold back to the grid. Heat generated by the engines can be recovered and used to heat digesters and plant facilities.

In anaerobic digestion, a process many wastewater treatment plants use in purification, usable methane gas is produced as a byproduct. Johnson Controls digester gas solutions can help you take advantage of this gas byproduct by converting it into energy. Wastewater treatment plants can use digester gas to supply the heat needed to complete the digestion process itself, to generate electricity, or do both.

Is this the right technology for my situation?

For digester gas to be a viable option, wastewater treatment plants should have a capacity of 25 to 75 million gallons per day and serve 150,000 to 500,000 people (this is typically a large city or regional facility).

Digester Gas facts:

There are 16,000 wastewater treatment plants in the United States. More than 3,500 of them employ anaerobic digestion but only two percent utilize the digester gas byproduct to produce electricity. Wastewater treatment plant gas-to-energy projects can provide immediate and long-term benefits, including:

  • Energy cost savings
  • Progress toward environmental
  • Energy security – When digester gas is piped directly to its end use, it provides security from interruptions in the gas and electric grids. Digester gas systems provide the lowest cost while still accommodating a steady base load for facilities that require back-up or standby electricity generation.
  • Utility cost stabilization – Wastewater treatment plant digester gas solutions provide an excellent hedge against fluctuations in fuel and electricity prices.
  • Environmental benefits – Significant reductions in greenhouse gas emissions since the methane from wastewater is 25 times more harmful to the atmosphere than carbon dioxide.

(Source: Federal Energy Management Program – FEMP Focus)

FEATURED CASE STUDY
Back River Wastewater Treatment Plant (PDF)
Baltimore, Maryland

Johnson Controls has developed a combined heat and power plant in Baltimore that uses the residual of treated wastewater as fuel.
RESOURCES
Turning digester gas into energy (PDF)

Johnson Controls digester gas solutions can help you take advantage of this gas byproduct by converting it into energy.
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