
While this story has not been verified, it is true that cocoa mulch can be harmful to pets. The lethal ingredient is "theobromine," and the cacao bean shells contain potentially toxic quantities of theobromine, a xanthine compound similar in effects to caffeine and theophylline. It is fairly well known that some animals should not eat chocolate and, according to the experts, that warning applies to cocoa mulch as well.
Most packaging of cocoa mulch makes it clear that it's not for human or animal consumption. It also appears that all cocoa mulch is not the same. One manufacturer, the maker of Mirana cocoa mulch, said that their mulch is the result of a series of processing steps and that the level of theobromine in their mulch is barely detectable.*
*www.truthorfiction.com - Cocoa Mulch harmful to pets