Device for biologically transforming pyrogasification gas into biogas comprising: - a liquid digestate production unit , comprising a raw digestate production unit and a phase separation system , with the joint function of producing liquid digestate containing anaerobic bacteria, - an RLMB functional unit comprising four functions: (i) a cooling function R of the pyrogasification gas , (ii) a washing function L of the pyrogasification gas , (iii) a methanisation function M of at least a portion of the by-products of the pyrogasification gas SPGP , extracted from the pyrogasification gas by the cooling function R and washing function L, so as to form biogas , (iv) a biomethanation function B of the syngas , extracted from the pyrogasification gas and separated from the by-products of the pyrogasification gas SPGP by the cooling function R and washing function L, so as to form biogas , the RLMB functional unit being supplied by at least the pyrogasification gas , and by digestate originating wholly or partly from the liquid digestate production unit , the RLMB functional unit comprising one or more separate sub-units each capable of performing all or some of one or more of the cooling, washing, methanisation and/or biomethanation functions. - a liquid digestate production unit , comprising a raw digestate production unit and a phase separation system , with the joint function of producing liquid digestate containing anaerobic bacteria, - an RLMB functional unit comprising four functions: (i) a cooling function R of the pyrogasification gas , (ii) a washing function L of the pyrogasification gas , (iii) a methanisation function M of at least a portion of the by-products of the pyrogasification gas SPGP , extracted from the pyrogasification gas by the cooling function R and washing function L, so as to form biogas , (iv) a biomethanation function B of the syngas , extracted from the pyrogasification gas and separated from the by-products of the pyrogasification gas SPGP by the cooling function R and washing function L, so as to form biogas , the RLMB functional unit being supplied by at least the pyrogasification gas , and by digestate originating wholly or partly from the liquid digestate production unit , the RLMB functional unit comprising one or more separate sub-units each capable of performing all or some of one or more of the cooling, washing, methanisation and/or biomethanation functions. (i) a cooling function R of the pyrogasification gas , (ii) a washing function L of the pyrogasification gas , (iii) a methanisation function M of at least a portion of the by-products of the pyrogasification gas SPGP , extracted from the pyrogasification gas by the cooling function R and washing function L, so as to form biogas , (iv) a biomethanation function B of the syngas , extracted from the pyrogasification gas and separated from the by-products of the pyrogasification gas SPGP by the cooling function R and washing function L, so as to form biogas , the RLMB functional unit being supplied by at least the pyrogasification gas , and by digestate originating wholly or partly from the liquid digestate production unit , the RLMB functional unit comprising one or more separate sub-units each capable of performing all or some of one or more of the cooling, washing, methanisation and/or biomethanation functions. the RLMB functional unit being supplied by at least the pyrogasification gas , and by digestate originating wholly or partly from the liquid digestate production unit , the RLMB functional unit comprising one or more separate sub-units each capable of performing all or some of one or more of the cooling, washing, methanisation and/or biomethanation functions. <EOS>