The Sacramento, CA-based Renewable Natural Gas (RNG) Coalition now boasts more than 100 members nationally with the addition of Duke Energy and Southwest Gas Corp. Southwest Gas provides natural gas utility services to more than two million customers in Nevada, Arizona and California, and Duke supplies gas utility services to more than 1.5 million customers in the Carolinas, Ohio, Kentucky and Tennessee. The companies join other RNG supporters that include utilities, energy/environmental organizations and universities.