General Mills -- Murfreesboro, Tennessee
This facility combines anaerobic pretreatment with a combined heat and power (CHP) system to convert Greek yogurt whey into heat and electricity. CHA teamed with CHA Tech Services to complete the design/build construction of this methane recovery project.
The facility feeds whey 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 1.6 MW CAT generator, with the electricity transformed to 4160V and used on site. While some heat is lost in the process, 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 wastes, CHA, CHA Tech Services and General Mills have developed a system that processes leftover whey to generate approximately 10% of the plant’s overall electrical needs. Excess heat recovered from the biogas generator has reduced the plant’s dependence on natural gas and reduced its usage of diesel fuel by 95,000 liters annually. 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. Furthermore, the waste-to-energy system reduces greenhouse gas emissions by about 9,000 metric tons per year and creates significant annual cost savings.
- 2017 ACEC New York Diamond Award - Energy