Marine fish such as mackerel are important for coastal fisheries in Taiwan. Nearly 60,000 tons of mackerel are produced in Suao, I-lan, Taiwan every year. In this study, oil from the discarded parts of mackerel fish contained in wastewater stream were used as the raw material to produce biodiesel through transesterification reaction. The major fuel properties of MB (mackerel biodiesel), including the iodine value, dynamic viscosity, flash point, and heat value, were determined and compared with sunflower seed oil methyl ester (SFM), JCB (jatropha curcas biodiesel), and premium diesel (D). MB had a higher iodine value, dynamic viscosity, density, and flash point, but a lower heat value, than did D. MB was also used as fuel in a regular diesel engine to verify its emission characteristics.-The MB fuel used for exhaust emission test included pure MB (MB100) and a 20% MB blend with premium diesel (MB20). The exhaust emission of MB was also compared with the exhaust emissions of D and JCB. The results showed that MB20 provided a significant reduction in NO, NOx, and SO2 emissions under varied engine loads, and required no engine modification. (C) 2014 Elsevier Ltd. All rights reserved.