Sign up for daily news updates from CleanTechnica on email. Or follow us on Google News!. Blame it on California. Its Air Resources Board (CARB) has been pushing to clean up emissions for diesel-powered heavy trucks for years. A significant amount of the goods that enter the United States from foreign countries every year arrive in ports in California. They cross the ocean in diesel-powered ships, are unloaded by diesel-powered cranes, are shunted around the receiving yards, then are hauled to inland transportation hubs by diesel-powered tractors before being distributed across the nation by other diesel-powered trucks. In addition, virtually all the trash-hauling trucks, cement mixers, dump trucks, school buses, and construction equipment in the Golden State are powered by diesel engines.