Method for converting brown coals, including leonardite, into humic fertilizers and fuel briquettes, comprising first grinding the raw material to less than 3 mm and subsequently treating it with water or water solutions, using liquid-phase mechanoactivation and/or mechanochemical activation, with a duty of water curve ranging from 0.9 to 2.5 and with reaction composition dispersion by chafing and dynamic shift by exposing the medium to a hydraulic impulse of sonic and infrasonic frequencies, by metered introduction of 10 to 40 MJ per cubic meter of mechanical energy, with automatic limitation of the energy in the sub-cavitation area for preventing the mechanochemical reactors from falling into cavitation modes; the method further comprises separation of converted suspension compositions into solid and liquid phases in the centrifugal force field, optionally acidizing the liquid phase with the withdrawal of humic acids from the liquid phase to the heavy phase and recycling of residual water.