San Francisco: Apple is cleaning up the way its manufacturing operations in China are powered so it can reduce air pollution from factories that have assembled hundreds of millions of iPhones, iPads and iPods. The world’s most valuable company is working with its Chinese suppliers to produce 2.2 gigawatts of solar power and other renewable energy by 2020. The commitment announced yesterday represents Apple’s latest attempt to prevent the popularity of its devices and digital services from increasing the carbon emissions that are widely believed to changing the Earth’s climate. Apple Inc estimates 20 million metric tons of greenhouse gas pollution will be avoided in China between now and the time all the projects are completed. That’s like having four million fewer cars on the road for a year.