Journal of Energy Bioscience 2025, Vol.16, No.5, 216-226 http://bioscipublisher.com/index.php/jeb 220 Figure 1 Schematic illustration of the biodiesel production process by transesterification and the parameters for the process and biodiesel characterization. KOH (potassium oxide); R-OH (alcohol) (Adopted from Khan et al., 2023) 6.2 Implementation: overview of local biodiesel industry and use of rapeseed oil as primary feedstock The biodiesel industry in Germany is very mature, and rapeseed oil is the main raw material. The production process is mainly based on alkal-catalyzed ester exchange. Under optimized conditions (such as a methanol/oil molar ratio of 6:1, KOH concentration of 1.0%, and temperature of 65 ℃), the yield can reach 95%~96%, and the products comply with the EU EN and the US ASTM standards (Rashid and Anwar, 2008; Khan et al., 2023). In recent years, there has been an increasing amount of research on green diesel. This type of fuel is obtained through catalytic deoxidation and has better compatibility and storage stability (Stiemicek et al., 2009; 2010; Di Vito Nolfi et al., 2025). 6.3 Findings: production scale, policy support, cost-effectiveness, adoption challenges In terms of production scale, Germany has both large centralized factories and small local production sites. Greenhouse gas emissions (GWP) from large-scale factories are approximately 2.63 tCO2-eq/t of biodiesel, while those from small-scale factories are 2.88 tCO2-eq/t (Gupta et al., 2022) (Figure 2). In terms of policies, the governments of the European Union and Germany have promoted the development of the biodiesel industry through measures such as the Renewable Energy Directive, and set targets and provided subsidies (Konur, 2021). Economic analysis shows that for a factory with an annual output of 50, 000 tons, the return on investment can reach 79.5%, and the unit cost can be reduced to $722~$945 per ton (Santaraite et al., 2020). However, there are also some challenges, such as competing with the food industry for raw materials, environmental pressure caused by the use of nitrogen fertilizers, high production energy consumption, poor fluidity at low temperatures, etc. (Stiima Cek et al., 2010; Lovasz et al., 2023). 6.4 Impact: contribution to renewable energy targets, reduction in emissions, socio-economic benefits The promotion of rapeseed biodiesel has significantly increased the proportion of renewable energy in the transportation sector in Germany, contributing to the EU's goal of reducing greenhouse gas emissions by 55% by 2030 (Makarevi Cienet al., 2024). Compared with mineral diesel, biodiesel has lower carbon emissions throughout its life cycle, with the agricultural stage accounting for more than 65% of the total emissions. Emissions can be further reduced by 14%~33% through optimizing planting methods and by-product utilization (Gupta et al., 2022). In addition, the biodiesel industry can also increase agricultural income, promote rural employment and enhance energy security, but food safety also needs to be taken into account (Santaraite et al., 2020; Lovasz et al., 2023).
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