Method for the treatment of animal slurries for obtaining a high calorific value product, in the form of lignin pellets or briquettes, comprising the following steps: (i) feeding material to a physical and/or chemical washing tank, wherein the feeding is selected from step a), step b), or step c): a) conveying material from a basin to the physical and/or chemical washing tank via a conveyor screw having a liquid filter; b) pumping material from a basin through a hose to a first liquid and solid separator, supplying water to the first liquid and solid separator to obtain a first liquid fraction and a first solid fraction, and depositing the first solid fraction in the physical and/or chemical washing tank; c) supplying material to the physical and/or chemical washing tank, wherein the waste material is waste from liquid and solid separators derived from basins and/or biogas plants or duff accumulation; (ii) supplying a continuous flow of water to the physical and/or chemical washing tank; (iii) washing the material by rotary movements and ultrasound and water drag to obtain a clean material; (iv) separating the clean material in a second liquid fraction and a second solid fraction in a new liquid and solid separator tank having a magnetic plate; (v) pressing or centrifuging the second solid fraction to obtain a dewatered material; (vi) drying the dewatered material using hot air to obtain a dried material; (vii) shredding and pressing the dried material to obtain a processed material; and (viii) pelletizing the processed material to obtain lignin pellets. (i) feeding material to a physical and/or chemical washing tank, wherein the feeding is selected from step a), step b), or step c): a) conveying material from a basin to the physical and/or chemical washing tank via a conveyor screw having a liquid filter; b) pumping material from a basin through a hose to a first liquid and solid separator, supplying water to the first liquid and solid separator to obtain a first liquid fraction and a first solid fraction, and depositing the first solid fraction in the physical and/or chemical washing tank; c) supplying material to the physical and/or chemical washing tank, wherein the waste material is waste from liquid and solid separators derived from basins and/or biogas plants or duff accumulation; a) conveying material from a basin to the physical and/or chemical washing tank via a conveyor screw having a liquid filter; b) pumping material from a basin through a hose to a first liquid and solid separator, supplying water to the first liquid and solid separator to obtain a first liquid fraction and a first solid fraction, and depositing the first solid fraction in the physical and/or chemical washing tank; c) supplying material to the physical and/or chemical washing tank, wherein the waste material is waste from liquid and solid separators derived from basins and/or biogas plants or duff accumulation; (ii) supplying a continuous flow of water to the physical and/or chemical washing tank; (iii) washing the material by rotary movements and ultrasound and water drag to obtain a clean material; (iv) separating the clean material in a second liquid fraction and a second solid fraction in a new liquid and solid separator tank having a magnetic plate; (v) pressing or centrifuging the second solid fraction to obtain a dewatered material; (vi) drying the dewatered material using hot air to obtain a dried material; (vii) shredding and pressing the dried material to obtain a processed material; and (viii) pelletizing the processed material to obtain lignin pellets.