Multi-Factor Assessment for Energy Production of Various Napier Grasses: Influence of Species, Maturity Stage, and Fertilization

Napier grass ( Pennisetum purpureum ) is a premier bioenergy feedstock due to its high biomass productivity and agronomic flexibility. This study evaluates the energy potential of four species—Dwarf, Pak Chong 1, Bana, and the novel hairless Suvarnabhumi—by analyzing the interplay between agronomic management (harvest intervals of 60, 90, 120 days and binary fertilization) and electricity generation via dual energy conversion: thermochemical and biological (anaerobic digestion) pathways. Results demonstrated that Suvarnabhumi possesses superior potential across both pathways. Thermochemical characteristics of all species were similarly analyzed experimentally via gross calorific value (GCV), ranging from 3,219.1 to 3,718.3 kCal/kg TS. Suvarnabhumi exhibited the highest GCV (3,718.3 kcal/kg TS), resulting in a calculated electricity potential of 39.9 MWh/ha/y compared to 7.9-39.9 MWh/ha/y for the others. Conversely, biochemical methane potential assessment revealed an inverse relation between crop maturity and methane productivity. At 60 days harvested, Dwarf promoted the highest specific methane yield (299.0 m³/t VS), while others yielded 211.3-286.5 m³/t VS. Fertilization upregulated total biomass production of all treatments (p0.05) compared to harvest intervals and species selection. These variations significantly impacted area-based electricity potential; thus, Suvarnabhumi achieved a maximum biogas-based output of 42.4 MWh/ha/y compared to 9.3-38.5 MWh/ha/y for other species. These findings underscore the need to maximize bioenergy potential by precisely aligning species selection, harvest intervals, and fertilization strategies with the specific conversion processes. This result provides a pivotal framework for the economic viability of grass-based biorefineries, promoting sustainability by decarbonizing the energy sector and mitigating fossil fuel dependency.