# A Comprehensive Review of the Application Characteristics of Biodiesel Blends in Diesel Engines
## 5 Emission Characteristics
### Regulated Emissions
#### 5.1.4 Nitrogen Oxides
They found that that the biodiesel blends reduced NO\({}_{\rm x}\) emissions by an average of 7.4%. The main factors to reduce the NO\({}_{\rm x}\) were the exhaust gas temperature, the O\({}_{2}\) content, cetane number and biodiesel chemical structure. The emissions characteristics for regulated gases are shown in Table 3.  
On the other hand, to address the increased NO\({}_{\rm x}\) emissions of biodiesel, appropriate nano additives can be used to decrease NO\({}_{\rm x}\) emission of biodiesel. [PERSON] et al. reported that nanosized CZA2 (Ce\({}_{0.6}\)Zr\({}_{0.2}\)Al\({}_{0.26}\)O\({}_{2}\)) catalysts absorb heat, catalyze combustion and release oxygen under a higher load, reducing the amount of NO\({}_{\rm x}\) release (and also decreasing the emissions of HC and  
Figure 12: Effects of rapeseed oil biodiesel on nitrogen oxide (NO\({}_{\rm x}\)) emissions [38]. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Raw Materials**} & \multirow{2}{*}{**Blends**} & \multicolumn{6}{c}{**Trends Compared to**} \\  & & \multicolumn{3}{c}{**Conventional Diesel**} & \multicolumn{2}{c}{**Reference**} \\ \cline{3-7}  & & **HC** & **CO** & **NO\({}_{\rm x}\)** & **PM** & \\ \hline Waste cooking-oil biodiesel & D100, B10, B20, B30 & \(\downarrow\) & \(\downarrow\) & \(\uparrow\) & \(\downarrow\) & [103] \\ Soybean biodiesel & D2, B10, B20, B50, B100 & \(\downarrow\) & \(\downarrow\) & \(\uparrow\) & \(\uparrow\) & [4] \\ Palm oil & D100, B20, B100, PO20 & \(\downarrow\) & \(\downarrow\) & \(\uparrow\) & & [94] \\ Waste fish oil & D, B25, B50, B75, B100 & \(\downarrow\) & \(\downarrow\) & \(\uparrow\) & & [59] \\ B0, K85 MB5, K810, MB10, & \(\downarrow\) & \(\downarrow\) & \(\uparrow\) & & [88] \\ K10 MB10, K820, MB20 & \(\downarrow\) & \(\downarrow\) & \(\uparrow\) & & [86] \\ Pongamia biodiesel & D, B20, B40, B60, B80, B100 & \(\downarrow\) & \(\downarrow\) & \(\uparrow\) & [89] \\ Castor biodiesel & D, B20, B40, B60, B80, B100 & \(\downarrow\) & \(\downarrow\) & \(\uparrow\) & \(\uparrow\)\(\downarrow\) & [89] \\ Mustard oil biodiesel & D100, M10, M20, M30 & \(\downarrow\) & & \(\uparrow\) & \(\downarrow\) & [56] \\ Spirulina microalgae biodiesel & B0, B20, B40, B60, B80, B100 & \(\downarrow\) & \(\downarrow\) & \(\downarrow\) & \(\downarrow\) & [90] \\ Citrus sinensis biodiesel & D, B5, B10, B20 & \(\downarrow\) & \(\uparrow\) & & [95] \\ Camelia biodiesel & D, B7, B100 & \(\downarrow\) & \(\uparrow\) & & [93] \\ Candaola biodiesel & D, B5, B10, B15, B20 & \(\downarrow\) & \(\downarrow\) & \(\uparrow\) & \(\uparrow\) & [91] \\ Cymbopogon flexuosus biofuel & DF, C10, C20, C30, C40, C100 & \(\downarrow\) & \(\downarrow\) & \(\uparrow\) & \(\downarrow\) & [54] \\ Micromalgae Chlorella & PD, B20, B50, B100 & \(\downarrow\) & \(\downarrow\) & \(\downarrow\) & [96] \\ protothecoides biodiesel & Licella biofuel & R0, R5, R10, R20 & \(\uparrow\) & \(\uparrow\) & \(\downarrow\) & [92] \\ Aphanamixis polystachya oil & Diesel, APME5, APME10 & \(\downarrow\) & \(\downarrow\) & & [87] \\ Jatropha biodiesel & D100, JME5, JME10, JME20, & \(\downarrow\) & \(\downarrow\) & \(\uparrow\) & \(\downarrow\) & [110] \\ JME30, JME100 & & \(\downarrow\) & \(\downarrow\) & \(\downarrow\)\(\uparrow\) & \(\downarrow\) & [25] \\ Argemone biodiesel & D, AB10, AB20, AB30, AB50 & \(\downarrow\) & \(\downarrow\) & \(\uparrow\)\(\uparrow\) & \(\downarrow\) & [111] \\ New series of non-edible biodiesel & D, MD, WD, MWD & \(\downarrow\) & \(\downarrow\) & \(\uparrow\) & \(\downarrow\) & [111] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Emission characteristics of different fuels with biodiesel. (“\(\uparrow\)” means the emissions increase, “\(\downarrow\)” means the emissions decrease, and “\(\uparrow\)\(\downarrow\)” means emissions vary with operating conditions). CO) [112].