Hybrid biofuel formulations for reducing the environmental impact of emission‐uncontrolled stationary diesel engines

Abstract Stationary diesel engines remain important for agricultural, industrial, and power‐generation applications, yet limited emission‐control technologies can lead to elevated pollutant emissions and environmental burdens. For large existing fleets, engine replacement or extensive hardware upgrades may be impractical. This study investigates hybrid biofuel formulations as a fuel‐based strategy to reduce the environmental impact of existing stationary diesel engines. Two formulations were developed using waste cooking oil biodiesel, ethanol, n‐butanol, 2‐ethylhexyl nitrate (EHN), and multi‐walled carbon nanotubes (MWCNTs). FF‐1 consisted of 68 vol% diesel, 17 vol% waste cooking oil biodiesel, 10 vol% ethanol, and 5 vol% n‐butanol, while FF‐2 incorporated 3000 ppm EHN and 100 ppm MWCNTs into FF‐1. The formulations were experimentally evaluated under five load conditions, considering energy performance, combustion behavior, emissions, environmental impact rate, environmental damage cost, exergy efficiency, and sustainability index. Compared with diesel fuel, FF‐1 and FF‐2 reduced average NO X emissions by 38.5% and 21.1%, respectively, and CO emissions by 47.9% and 50.1%. Although brake‐specific fuel consumption increased by 4.3–6.1%, FF‐2 achieved 4.9% higher brake thermal efficiency than B20. FF‐1 and FF‐2 reduced the environmental impact rate by 36.16% and 24.89%, respectively, and the environmental damage cost by 21.46% and 16.42%. FF‐2 achieved a peak exergy efficiency (37.5%) and sustainability index (1.60). Overall, hybrid biofuels with functional additives can reduce pollutant emissions and environmental impacts of stationary diesel engines while promoting cleaner use of waste‐derived and renewable energy resources. However, some fuel‐property non‐conformities under EN590 and high fuel costs appear to be major constraints on their practical use.