A wastewater heat recovery system operates Tuesday, Dec. 2, 2025, at the National Western Center in Denver. (AP Photo/Brittany Peterson)A veterinarian works on an animal in a building that is heated and cooled by a wastewater heat recovery system Tuesday, Dec. 2, 2025, in Denver. (AP Photo/Brittany Peterson)A wastewater heat recovery system operates Tuesday, Dec. 2, 2025, at the National Western Center in Denver. (AP Photo/Brittany Peterson)The National Western Center is visible Friday, Nov. 21, 2025, in Denver. (AP Photo/Brittany Peterson)
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A wastewater heat recovery system operates Tuesday, Dec. 2, 2025, at the National Western Center in Denver. (AP Photo/Brittany Peterson)