The two companies at the top of credit leaderboard paid vastly different amounts and backed very different projects to achieve their ranking… Microsoft focused almost exclusively on carbon removal credits. Close to 80 percent of the credits it retired were from projects that generate energy by burning biomass and then capturing and storing the associated emissions. Because the biomass captures carbon dioxide as it grows, the process, known as bioenergy with carbon capture and storage (BECCS), can be carbon negative. Shell focused on projects that avoided greenhouse gas emissions. The company retires credits to offset its emissions and, unlike Microsoft, also helps clients acquire credits. It used more established credit types, retiring 9.4 million forestry and land use credits and 2.4 million renewable energy credits.