According to the Charlotte Observer, Apple has filed for permission to double the size of its on-site fuel cells to allow them to produce 10 megawatts of power. The fuel cells make use of direct biogas, a fancy way of saying that the by-product from nearby landfills is being used as the methane source for the fuel cells.
Apple's original fuel cell system went into startup testing last October. Late in the startup testing phase, Apple applied for the increase in the number of on-site fuel cells and the eventual doubling of the power capabilities.
The Malden data center is also home to two large solar farms that are projected to supply up to 40 megawatts of power to the Apple data center. Combined with the fuel cells, that brings the total power created at the Apple site to 50 megawatts, all from renewable energy sources.