Comparative Performance and Emission Analysis of Soybean and Algae Biodiesels in Low Heat Rejection Engines

ABSTRACT The quest for sustainable energy solutions has driven extensive research into biodiesel derived from renewable sources such as soybean oil and algae. This study aims to optimize biodiesel production from soybean oil and algae using transesterification and pyrolysis processes. Additionally, it evaluates the performance and emission characteristics of these biodiesels in conventional and low heat rejection (LHR) engines to enhance the understanding of biodiesel production processes and their impact on engine performance and emissions. Soybean oil and algae were used as feedstocks for biodiesel production via transesterification and pyrolysis. The produced biodiesels, specifically soybean methyl ester (SBME), algae methyl ester (ALME), and soybean pyrolytic oil (SBPO), were tested in both conventional and LHR engines. Performance metrics such as brake‐specific fuel consumption (BSFC), brake thermal efficiency (BTE), exhaust gas temperature (EGT), and emissions (CO, HC, NOx) were analyzed. SBME20 blend demonstrated superior performance with lower BSFC, higher BTE, and reduced CO and HC emissions compared to ALME20 and SBPO20 blends. However, NOx emissions were higher in LHR engines due to increased combustion temperatures. The LHR engine's enhanced thermal environment improved fuel combustion efficiency, particularly for SBME20, which exhibited the best overall performance and emission profile. The study concludes that SBME20 is the most efficient and environmentally friendly biodiesel blend for LHR engines, highlighting the potential of soybean oil as a viable feedstock for sustainable biodiesel production. Further optimization is required for ALME20 and SBPO20 to achieve comparable performance levels.