A high content of minerals in biomass feedstock may cause fouling, slagging, and corrosion in the furnace during combustion. Here, a new pressurized microwave digestion method for biomass digestion prior to elemental analysis is presented. This high-throughput method is capable of processing approximately 48 samples per hour with reduced laboratory hazards and waste because only a very small volume of hydrofluoric acid is used. Concentrations of 12 elements (Al, Ca, Cd, Cu, Fe, K, Mg, Mn, Na, P, Si, and Zn) were determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES). National Institute of Standards and Technology (NIST) standard reference materials (SRMs) 1515 apple leaves and 1575a pine needles were used for method validation. Recoveries of the 12 elements in the NIST SRMs ranged from 93 to 115%. A comparison of the high-throughput method with the European Union (EU) standard method showed agreements in the range from 98 to 115% (except for Al) when the elements were quantified in plant material of the energy crop Miscanthus x giganteus.