A renewable diesel plant, using second generation biofuels and NEXBTL technology and located at the Porvoo refinery, was brought on stream in 2007, together with a new conventional diesel production line. At the same year, the entire bus fleet of Helsinki Region Transport switched fully to diesel produced using NEXBTL technology. Experiments by Neste, VTT Technical Research Centre of Finland and Proventia showed that local emissions decreased significantly after the switch, with overal particle emissions decreasing by 30% and nitrogen oxide emissions by 10%, with excellent winter performance and no problems with catalytic converters. A second renewable diesel plant at Porvoo was became operational in 2009.