# Biological Methods in Biodiesel Production and Their Environmental Impact
## 4 Environmental Impact  
The environmental impact of the biodiesel production process largely depends on two factors: the type of raw material and the production technology used. In the case of a raw material, the origin of the raw material has an impact on the lifecycle emission performance. The use of advanced raw materials for the production of biofuels having the status of waste or residue results in a higher reduction of greenhouse gas emissions (compared to biofuels produced from food raw materials). If, on the other hand, the raw material is cultivated on purpose, then its acquisition carries a burden on the environment related to, inter alia, the production and use of fertilizers and plant protection products or the combustion of diesel oil during the operation of agricultural machinery. Table 2 shows the impact of the origin of the raw material on the result of GHG emissions in the biodiesel lifecycle [73]. Regardless of the raw material used for the production of biodiesel, it is characterized by a much lower greenhouse gas emission compared to conventional diesel oil (Table 2). Another aspect influencing the emission result in the biodiesel lifecycle is the technological process. This issue was raised in the literature on the subject, inter alia, by the authors of [74]. The publication presents the results of a comparative environmental lifecycle assessment of two types of biodiesel production processes: enzyme-catalyzed biodiesel production and the alkali-catalyzed biodiesel production technology. In all environmental impact categories, the results were much more favorable for enzyme-catalyzed biodiesel production (Figure 3). Such a result is mainly due to the higher efficiency as well as a shorter course of the enzymatic reaction, a lower reaction temperature, and the lack of alkali compounds, the production of which carries a significant burden on the environment. The only exception is in the respiratory organic category, because of the higher quantity of methanol present in the emission of air for enzyme-catalyzed biodiesel production. The added value of the enzyme-catalyzed biodiesel is also that the reusability of the enzyme will decrease the need for new catalysts, and it is much cleaner from the emission perspective. This LCA study provides additional supportive information that the enzyme-catalyzed biodiesel production contributes less impacts to the environment due to the fact that chemical catalysts and neutralizing acid are not required in the process [74]. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Biodiesel Production Pathway** & **Default GHG Emission (gCO2 eq/MJ)** & **Default GHG Saving (\%)** \\ \hline rape seed biodiesel & 52 & 38 \\ sunflower biodiesel & 42 & 51 \\ soybean biodiesel & 58 & 31 \\ palm oil biodiesel (process not specified) & 68 & 19 \\ palm oil biodiesel (process with methane capture at oil mill) & 37 & 56 \\ waste vegetable or animal oil biodiesel & 14 & 83 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: GHG emission value and emission reduction in relation to fossil fuel analogue throughout the lifecycle of biodiesel, taking into account the type of raw material [73]. Figure 3: Results of the comparative lifecycle analysis of enzyme-catalyzed biodiesel production and the alkali-catalyzed biodiesel production technology [74]. The authors of [75] also point to a much lower impact on the environment of the enzyme-catalyzed biodiesel. The authors of the article conducted a comparative environmental impact analysis of the soybean biodiesel production by two different technologies. The production routes evaluated were the alkali-catalyzed (catalyst: sodium hydroxide) methylic transesterification and the enzyme-catalyzed (catalyst: lipase) ethylic transesterification.