When a wastewater treatment plant (WWT) is combined with a cogeneration system, the benefits can be considerable: first and foremost, the cost of energy is reduced, as electrical and thermal energy is produced alternately from a single source; second, the CO2 emissions into the atmosphere are reduced; and lastly, the plant’s resilience is improved, which can continue to function even in case of a black out. All these advantages are further amplified when the cogeneration plant is powered by biogas, possibly exploiting the sludge derived from the water purification process. A concrete case of biogas from a WTT is that of the East Bay Municipal Utility District (Oakland, CA), which you can read in this PDF published by the CHP Alliance. Source: Cogeneration Channel