Within the past year, both European and U.S. officials have investigated the cement industry for price collusion, anti-trust issues and other unfair business practices. Now, new studies from environmental consultants CE Delft and Sandbag say LaFarge-Holcim, HeidelbergCement Group, Cemex and others made billions of dollars passing through costs of carbon pollution limits to customers—mostly concrete mixers and contractors—even as they received credits for free.

The cement suppliers vigorously deny it, saying they have not profited from or manipulated the carbon market.