Justification of the optimal harvesting times for Miscanthus giganteus biomass based on quality, economic, and energy efficiency indicators

The growing environmental challenges are prompting humanity to seek ways to reduce the use of fossil fuels by turning to renewable energy sources, including high-yield perennial bioenergy crops. The aim of this study was to improve the economic and energy efficiency of Miscanthus giganteus production by optimizing biomass harvest timing, taking into account yield dynamics, moisture loss, and quality criteria for processing into solid biofuel. The study employed field, laboratory, and statistical methods. The research was conducted in a temperate-continental climate zone with annual precipitation ranging from 500 to 800 mm and an average annual air temperature of +6-7 °C. It was established that harvesting Miscanthus giganteus for processing into solid biofuel is recommended before the onset of new shoot growth (March-April). This reduces the biomass moisture content from 56.3% to 18.3% and, accordingly, decreases the biomass yield at natural moisture content from 45.1 to 22.4 t/ha, and the dry matter yield from 19.7 to 18.3 t/ha. At the same time, the ash content of the biomass decreases from 2.8 to 0.7%, the specific heat value increases from 7.6 to 15 MJ/kg, and the profitability of pellet production rises from 54.5 to 72.6 percent. Based on five years of experimental data, empirical relationships were established between moisture content (R² = 0.957), wet biomass yield (R² = 0.993), and dry biomass yield (R² = 0.962) and the timing of harvest.