Not long ago, the wastewater treatment plant was the biggest power user in municipal operations for the city of Gresham, Ore. Then, 12 years ago, the city entered into a long-term sustainability partnership with Veolia and began the process of turning the city’s energy hog into an energy asset. First step was a cogeneration system that met about half of the power needs of the plant. Five years ago, the city brought in fats, oils, and greases (FOG) from food manufacturers as an additional organic source of biogas, co-digested with sewage sludge through anaerobic digestion. It was a natural fit: the heat from the cogeneration system kept the FOG from hardening as they were processed. Five years and 9,000 gallons of biogas per day later, Gresham’s wastewater treatment plant is now “net-zero,” generating at least as much power as it uses.