Marine waste valorization through nanocatalytic and ammonia‐assisted combustion: Toward sustainable and low‐emissions energy systems

A sustainable, low‐carbon combustion strategy is proposed that integrates fish‐waste biodiesel, nitrogen‐doped multi‐walled carbon nanotubes (N‐MWCNTs), and ammonia (NH 3 ) fumigation to enhance combustion efficiency and reduce emissions in diesel engines. Specifically, the study investigates nanocatalytic and hydrogen (H 2 ) assisted mechanisms for NH 3 decomposition, aiming to improve efficiency and reduce pollutant emissions. To test these mechanisms, experiments were conducted using a single‐cylinder, four‐stroke diesel engine operating at 1500 rpm. The test fuels included diesel, biodiesel (B100), and B100 blended with 40, 80, and 120 ppm N‐MWCNTs. Additionally, all fuels were evaluated under constant NH 3 fumigation at 5 LPM. At maximum load, results showed that the optimized tri‐fuel blend (B100 + N‐MWCNTs 120 ppm + NH 3 5 LPM) achieved a 7.8% higher maximum cylinder pressure and a 13.5% higher heat release rate (HRR) than diesel, and 12.5% and 22.3% higher than B100, respectively. Furthermore, brake thermal efficiency (BTE) increased by 15.4% compared to diesel and 29.2% compared to B100, while brake specific energy consumption (BSEC) decreased by 22.3% and 35.6%, respectively. With respect to emissions, reductions in carbon monoxide (CO), hydrocarbons (HC), and smoke opacity were observed: 38%, 12%, and 37% lower than with diesel, and 30.6%, 5%, and 28.6% lower than with B100, respectively. However, oxides of nitrogen (NO x ) emissions increased by 31.1% over diesel and 22.7% over B100. Collectively, nanocatalytic oxidation by N‐MWCNTs and H 2 enrichment from NH 3 decomposition improved performance and reduced emissions. These findings indicate that the tri‐fuel system represents a scalable waste‐to‐energy pathway consistent with the Sustainable Development Goals.