Method for upgrading biomass or substrates at least partially organic and at least partially solid, comprising steps consisting in: A. introducing a plurality of volumes of fresh substrates in a plurality of respective strainers, B. humidifying the volume of substrates of at least one strainer, in order to ensure a hydrolysis of at least a portion of the organic constituents of said volume, C. injecting the leachate from at least one humidified volume of substrates into an anaerobic digester in order to produce biogas, D. sending at least a portion of the liquid from the anaerobic digester into at least one strainer for the step B, and E. repeating the steps B to D for a determined duration, with the substrates being left as is in the strainer, without crushing or mechanical stirring beforehand or in the strainer, said method being characterised in that it further comprises: - a step of chemically analysing the leachate used for the step B of humidification, which makes it possible to provide an indication on the methanogenic potential of a volume of substrate, and - a step of measuring the temperature of the substrates in said strainer, and in that beyond a threshold time value, for a volume of substrates of at least one of said strainers, said method further comprises steps consisting in: F. a step of aerobic fermentation consisting in providing a first phase of composting of said volume of substrates in said strainer via aerobic fermentation implemented by stopping the humidification of the strainer and by aerating said strainer, and G. a step of aerobic maturation consisting in providing a second phase of composting of said volume of substrates par aerobic maturation, by withdrawing said fermented volume of substrates from said strainer and by positioning said volume in an aerobic storage device in order to obtain a stabilised compost, of which the humidity rate is less than a maximum threshold value and/or greater than a minimum threshold value, and in that, for the step C, all the leachate from said humidified volume of substrates being injected directly into the anaerobic digester, the step F being dependent on the step of chemical analysis and being implemented according to the result of this step of chemical analysis of the leachate, for example according to the difference between a threshold value and the absolute value of the difference between a reference value and the value of the result of the step of chemical analysis of the leachate, said step F ending when the temperature of the substrates in said strainer is greater than a threshold temperature value, and the implementing of the step G being dependent on the results of the step of measuring the temperature at least during the step of aerobic fermentation and beginning after the realisation of the step E and F. A. introducing a plurality of volumes of fresh substrates in a plurality of respective strainers, B. humidifying the volume of substrates of at least one strainer, in order to ensure a hydrolysis of at least a portion of the organic constituents of said volume, C. injecting the leachate from at least one humidified volume of substrates into an anaerobic digester in order to produce biogas, D. sending at least a portion of the liquid from the anaerobic digester into at least one strainer for the step B, and E. repeating the steps B to D for a determined duration, with the substrates being left as is in the strainer, without crushing or mechanical stirring beforehand or in the strainer, - a step of chemically analysing the leachate used for the step B of humidification, which makes it possible to provide an indication on the methanogenic potential of a volume of substrate, and - a step of measuring the temperature of the substrates in said strainer, F. a step of aerobic fermentation consisting in providing a first phase of composting of said volume of substrates in said strainer via aerobic fermentation implemented by stopping the humidification of the strainer and by aerating said strainer, and G. a step of aerobic maturation consisting in providing a second phase of composting of said volume of substrates par aerobic maturation, by withdrawing said fermented volume of substrates from said strainer and by positioning said volume in an aerobic storage device in order to obtain a stabilised compost, of which the humidity rate is less than a maximum threshold value and/or greater than a minimum threshold value, and