# Biological Methods in Biodiesel Production and Their Environmental Impact
## 4 Environmental Impact
The results of the lifecycle regarding material consumption and the evaluation of impact categories such as the greenhouse effect potential (GEP), the potential of ozone layer depletion (OLD), the potential of ozone photochemical formation (OPF), nonrenewable energy usage (NEU), liquid effluents' generation (LEG), solid waste generation (SWG), and the acidification potential (ACP), indicated the environmental benefits of the ethanol usage instead of methanol and of the enzymatic technology over the traditional alkaline technology [75]. These benefits are visible in all categories, with the exception of the potential of ozone photochemical formation of the methylic route (Figure 4). This result is mainly because of the methanol production, where hydrocarbons are released during natural gas processing. On the other hand, the most favorable results were obtained for the ethylic route in the GEP category. The ethylic route presents a negative value connected to the carbon sequestration during two agricultural stages: soybean production and sugarcane production. The methylic route presents a significant positive contribution to the carbon dioxide release from the methanol production processes [75]. The authors of [76] emphasize the impact of the type of raw material and its origin on the total result of emissions in the whole lifecycle. The alkali-catalyzed biodiesel production process, where the virgin soybean oil was used as a substrate (Case 1), with enzyme-catalyzed biodiesel produced from virgin soybean oil (Case 2), and with waste cooking oil (UCO) (Case 3), was subjected to LCA analysis. The LCA included the following impact categories: Global Warming Potential (GWP), Ozone Layer Depletion Potential  
Figure 4: Comparative environmental impact analysis of the soybean biodiesel production by two different technologies: the alkali-catalyzed methylic transesterification and the enzyme-catalyzed ethylic transesterification for two different localizations, where NEU is non-renewable energy usage, LEG—liquid effluents’ generation, SWG—solid waste generation, GEP—the greenhouse effect potential, OLD—the potential of ozone layer depletion, OPF—the potential of ozone photochemical formation, and ACP—the acidification potential [75]. (ODP), Photochemical Ozone Creation Potential (POCP), Human Toxicity Potential (HTP), Abiotic Depletion Potential (ADP), Fresh Water Aquatic Ecotoxicity Potential (FAETP), Marine Aquatic Ecotoxicity Potential (MAETP), Terrestrial Ecotoxicity Potential (TETP), Acidification Potential (AP), and Eutrophication Potential (EP) [76]. The obtained results show a clear environmental advantage of the enzyme-catalyzed biodiesel produced from UCO in all the above-mentioned impact categories (Figure 5). This result is mainly influenced by the waste origin of the UCO, and thus the zero GHG emission attributed to the remaining raw material stage. The category where the environmental advantage of biodiesel made from UCO over biodiesel made from soybean oil is particularly prominent is GWP100. The agricultural stage related to the cultivation of soybean has the main influence on this result. This result is related to the necessity of intending land for soybean cultivation and the use of mineral fertilizers and plant protection products, for which production and application of the plantation is energy-intensive and results in significant emissions of particulate matter and gases into the air. From the analysis results, the fuel combustion, mainly diesel fuel, also has a significant influence during field work. The results of the environmental lifecycle assessment of various biodiesel production technologies presented above show that biodiesel produced with the enzymatic method is characterized by much more favorable environmental parameters [74; 75; 76]. The main advantage of the enzymatic method over the alkaline or acidic method is, inter alia, the lower temperature of the process, which in turn translates into lower GHG emissions associated with the need to provide less heat to the process.