General Mills, Inc. Yogurt to Methane Gas-to-Energy

The General Mills, Inc. facility combines anaerobic pre-treatment with a combined heat and power (CHP) system to convert Greek yogurt whey into heat and electricity. Whey is fed to bacteria in an on-site industrial pre-treatment anaerobic digester, which breaks down the whey and reduces the amount of sludge produced, improving the quality of wastewater and generating useful methane bios. The collected biogas is dried, compressed, cooled, and conveyed to a CHP generator at a new energy recovery site. Excess biogas is flared before the remainder is used to fire a 1,600 kW CAT generator, with the electricity transformed to 4160V and used on site. While some heat is lost, most is recovered through a heat recovery loop and supplements the plant’s high-temperature hot water (HTHW) system.

By rethinking typical approaches to handling waste, CHA developed a system that processes leftover whey to generate approximately 10% of the plant’s overall electrical needs. In addition to costs saved by eliminating the need for off-site disposal, millions of gallons of water have been returned to the watershed, and several thousand acres of farmland have been made available for agricultural use.