The invention discloses a binder-free preparation method for preparing a composite carbon-based
fertilizer by using
biogas residues, which comprises the steps of conducting pretreatment, specifically, collecting
biogas residues after
solid-liquid separation, air-
drying and crushing to obtain dried
biogas residue
powder; performing high-temperature
pyrolysis, specifically, transferring the pretreated dried biogas residue
powder into a
muffle furnace, and performing
pyrolysis for a period of time under a
pyrolysis temperature condition to obtain a biogas residue
biochar material; preparing a biogas residue carbon-based compound
fertilizer; and carrying out
granulation preparation, specifically, placing the prepared composite biogas residue
biochar base
fertilizer in an
extrusion die, and performing
granulation under certain compression speed and pressure conditions to obtain the granular composite biogas residue
biochar base fertilizer. The biogas residues are utilized for
reproduction, and the environmental and economic burden is relieved; the process is simple, and the cost is low; a binder is not added, so that the method is environment-friendly;
powder is granulated, so that the transportation and application difficulties are solved; and meanwhile, the granules are dried at high temperature after being formed, nutrients are tightly combined with
charcoal functional groups, the
nutrient release time is prolonged, and the fertilizer quality is improved.