Crude Tall Oil based renewable diesel: performance, emission characteristics and storage stability

International policies aiming at replacing fossil fuels with bio-components are getting stronger. Hydrotreating of bio-oils is a modern way to produce premium quality diesel fuels from completely renewable feedstocks. The Finnish forestry company UPM has developed an innovative production process based on hydrotreatment to convert crude tall oil (CTO) into a high-quality renewable diesel fuel that can be used as a blending component or as 100% fuel in all diesel engines without modifications. Paraffinic, high cetane CTO renewable diesel allows efficient and clean combustion, reducing harmful air emissions in addition to not releasing any new CO2 into the atmosphere. Fuels are expected to be of high quality and to remain stable even after long term storage. Oxidation stability is one of the most important properties that affect the stability of fuel during extended storage. Oxidation processes are initiated or accelerated by various factors, such as temperature and light, and lead to the formation of undesired reaction products that may impair fuel quality and engine performance. As CTO renewable diesel contains practically no oxygen, it is considered stable for prolonged storage. This study investigated the effect of CTO renewable diesel (BVO) on engine performance and exhaust emissions. Conventional market diesel (DFO) served as a reference fuel. An important aspect was to study the impact of long-term storage on BVO quality. Therefore, the BVO sample used in the experiments had been stored for four years. The research engine was a common-rail non-road diesel engine, operated by using the load points of the non-road steady state cycle of the ISO8178 standard. The use of BVO reduced all regulated emissions (NOx -9%, CO -6%, HC -7%). A significant 39% reduction was obtained in cycle-weighted particulate number. BVO did not show substantial storage stability problems; a relevant issue when selecting fuel for, e.g., seasonal machinery or emergency oil stocks.