 Unsaturated fatty acids are the source for the lower oxidation stability; they react with oxygen and form peroxides and result in degradation byproducts, which can cause sludge and lacquer in the fuel system.As biodiesel contains low levels of sulfur, the emissions of sulfur oxides and sulfates, major components of acid rain, are low.Use of biodiesel also results in reductions of unburned hydrocarbons, carbon monoxide (CO), and particulate matter.