The cells will be fueled by filtered methane gas from a local landfill, or "directed biogas" will be injected into a natural gas pipeline. The directed biogas is considered a renewable evergy resource that complies with North Carolina's green-energy regulations. Apple says phase one of the project, 4.8 megawatts of power generation, began testing in October. The computer manufacturer applied for a permit on November to enlarge the project. Excess power generated by the project will be sold to Duke Energy. Biogas isn't the only "green" energy source at the Apple data center in the state. Solar arrays will ultimately cover 250 acres, making them some of the largest in the industry. Apple sources also revealed that the company eventually intends to go coal-free at all three of its newest data centers.