Comparative analysis of energy, exergy, emission, and sustainability aspects of third generation microalgae biodiesels in a diesel engine

Abstract

Third-generation biodiesel produced from various microalgae species is being researched for its production, conversion, compatibility, sustainability, and environment-friendly behaviour for the diesel engine as a replacement of conventional diesel fuel. The present work is conducted with the objective of analysing a clean, green, and sustainable microalgae biodiesel for energy, exergy, emission, and sustainability assessment in a diesel engine system, along with the evaluation of air quality in terms of emission analysis for assessing its impact on climate. The fuel samples from diesel and the three microalgae species, viz., Chlorella emersonii, Euglena sanguinea, and Spirulina, are designated as DF100, CE100, ES100, and SP100, respectively. The engine behaviour is assessed and compared at 1500 rpm under 17.5 compression ratio with 25–100 % engine load. DF100 achieves the maximum energy and energy efficiency of 32.76 % and 30.74 %, respectively, and a varied range of 27.32–30.37 % and 25.28–28.10 % with microalgae biodiesels. The air quality is improved with the reduction of PM emissions by 15.82–27.09 % at the cost of improved nitrogen oxide (NOx) emissions by 11.03–15.55 %. The sustainability index is highest for DF100 (1.247–1.444), and among biodiesel fuel samples, it is highest for SP100 (1.233–1.391) at all engine loads. These results point to the possibility of microalgae-derived biodiesel blends as feasible diesel fuel substitutes, providing environmentally friendly and effective solutions for internal combustion engines.