Blackstone is exploring a $3 billion sale of Sphera, a sustainability software and consulting services provider, according to three people familiar with the matter. The private equity firm has hired investment bankers at William Blair and Evercore to run the sale, which is in its early stages, said the people who requested anonymity speaking about confidential matters. Blackstone declined to comment. Evercore, William Blair, and Sphera did not immediately respond to Reuters' request for comments.