ERG’s Clean Transportation Group helped the City of Portland, Oregon, take a major step toward eliminating fossil fuels with the nation’s first all-biofuel mandate for diesel engines. Upon deciding to shift away from petroleum-based diesel to support their aggressive climate action goals, the city turned to ERG to help assess the effect of this shift on local air pollution. Drawing from recent studies, ERG analyzed how switching to different biofuels would impact harmful emissions within Portland. The team found that fuel made from renewable sources, such as vegetable oil, greases, algae, and plant material, can reduce soot from diesel engines—which can cause cancer and respiratory illnesses—by 25 percent. Portland subsequently mandated the sale of renewable diesel within the city by 2030.