The aim of this study was to compare oxidation stability, emissions during engine tests and fuel properties of biodiesels. The biodiesels were produced from different raw materials using the transesterification process. The raw materials used were: salmon oil, fox fat, rainbow trout oil, rapeseed oil and linseed oil. The engine tests showed differences in emissions with different biodiesels. The fatty acid profiles were measured and their effect on oxidation stability and other fuel properties were noticeable. The effect of synthetic antioxidant was also measured for different biodiesels. The oxidation stability increase was related to the raw material used to produce the fuel. The oxidation stability of biodiesel blends was measured. The oxidation stability of the blended fuel increased when biodiesel with a higher oxidation stability level was introduced. These measurements indicate that oxidation stability can be enhanced with antioxidants and by blending diesel fuel or other biodiesels together.

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The demand for increased use of biofuels in both on- and off-road diesel engines is growing. The carbon dioxide emissions must be reduced, but the increase in the petroleum prices and possible shortage of crude oil also promote the interest in biofuels. Simultaneously, exhaust pollutants of diesel engines have to be drastically reduced. The nitrogen oxides (NOx) and particulate matter (PM) form the main challenge for diesel exhaust cleaning. Despite the emissions reduction, the fuel economy of the engines should be kept at a sufficient level to also prevent the CO2 increase. In the present study, a turbocharged, inter-cooled direct-injection off-road diesel engine was driven with two animal fat based bio-fuels, namely steelhead (or rainbow trout) methyl ester (StME) and crude steelhead oil (StO). Crude or neat biofuels are also of interest since medium-speed engines are able to burn unrefined bio-oils. A vegetable oil based fuel, canola oil methyl ester (RME) served as the main reference biofuel. The baseline results were measured with commercial low-sulfur diesel fuel oil (DFO). The main aim of the project was to clarify how the waste-derived animal fat based biofuels are suited to engine use. The performance and emissions characteristics of the engine were determined. In addition to regulated emissions, the particle size distributions were also examined. The results showed that the studied animal fat derived ester was very suitable for the off-road test engine. NOx increased but hydrocarbons (HC), smoke, and PM mass decreased (by up to 60%) while thermal efficiency and carbon monoxide (CO) remained approximately unchanged. The particle number emissions were competitive relative to DFO. Raw fish oil StO reduced HC emissions but increased NOx and particle mass and number emissions. CO and smoke behaved ambiguously, so further investigation is needed for this fuel.

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