Cymbopogon martini, also known as Palmarosa, is a grass species in the Cymbopogon genus, native to India and widely cultivated in tropical regions for oil production. Phytol, a constituent of chlorophyll, has garnered attention in the biofuels industry due to its potential for conversion into biodiesel through transesterification. Its abundance and renewable nature underscore its relevance for sustainable development. This study investigates the energy potential of waste Cymbopogon martinii Methyl Ester (CMME) in engine combustion systems using reactivity-controlled compression ignition (RCCI) in a single-cylinder, four-stroke diesel engine for low-temperature combustion. The process involves blending low-reactivity fuel (LRF), such as phytol (Acyclic diterpene alcohol and a constituent of chlorophyll), with high-reactivity fuel (HRF), namely CMME, in carefully monitored proportions. CMME25 is used as the primary fuel, supplemented with varying amounts of phytol (10 %, 20 %, and 30 %). Heat release rate (HRR) analysis indicates that phytol improves combustion efficiency up to a 20 % blend in RCCI mode. However, exceeding a 30 % phytol blend reduces brake thermal efficiency (BTE). RCCI mode also shows decreased nitrogen oxide and smoke emissions but increased hydrocarbon (HC) and carbon monoxide (CO) emissions. Improved homogeneity and ignition delay result in higher peak pressure and HRR compared to traditional methods. Further investigation focuses on the effects of CuO nanoparticles on a CMME25 and PHY20 % blend in RCCI mode. CuO nanoparticles (50–100 ppm) enhance brake thermal efficiency, improve combustion parameters (ignition delay, HRR, and cylinder pressure), and reduce emissions. The study concludes that a blend of CMME25+PHY20 % with 100 ppm CuO in RCCI mode is a promising alternative to traditional diesel fuel, offering a sustainable and efficient energy solution.