TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The mixture of waste comprises (wt.%) vegetation waters from olive oil production (5-25, preferably 20), active sludge from urban sewage purification (45-70, preferably 55), and putrescible organic fractions (18-35, preferably 25). Preferred Method: Anaerobic digestion is carried out at 35-40, preferably approximately 39 degrees C. The method further comprises an operation to feed the portion of reaction mixture extracted from the hydrogen production reactor to an anaerobic reactor for methane production, where the operation is conducted with an average residence time of the portion of reaction mixture in the methane production reactor for approximately 10-15 days at 35-40 degrees C. The method further comprises dehydrating, mixing with a bulking material, and sending to a composting station (17), the reacted mixture extracted from the methane production reactor. EXAMPLE - A mixture (1 kg) of putrescible organic fractions of urban waste (MSWOF) (250 g), vegetation waters from olive oil production (OMW) (200 g) and active sludge from urban sewage purification (AS) (550 g) was produced. The water content of this mixture was such that 1 L corresponded approximately 1 kg. Preparation of the mixture took place by first subjecting the MSWOF fraction (coming from separate waste collection or mechanical sorting) to a grinding process. The MSWOF fraction was sent to a heated mixer to which the OMW fraction and the AS fraction were also fed. The mixture thus obtained had total solids (ST) of approximately 6% and volatile solids of 91%; consequently 1 kg of mixture contains approximately 60 g total solids and approximately 58 g volatile solids. The mixture (1 L) was homogenized and transferred through a pump to a continuous stirred-tank reactor. The reactor, equipped with sensors to detect pH and temperature, as well as ports to take liquid and gaseous samples to check the trend of the biological process, was heated at 39 degrees C. Each day a volume of half the reactor volume ( approximately 0.5 L) was extracted, to set an average hydraulic retention time of the mixture in the reactor of 2 days. The volume of mixture extracted was replaced by the same volume of fresh mixture. The gas produced each day was measured volumetrically and its composition was analyzed using gas chromatography, to determine the hydrogen content. Hydrogen production was monitored for less than or equal to 60 days. The average hydrogen production in these experimental conditions was 70 normal liters (NL) of hydrogen per kg of volatile solids fed, i.e. approximately 4 NL hydrogen (H2) per kg of mixture fed. The average percentage of hydrogen in the gas produced was, in these operating conditions, 36% v/v, and the rest was carbon dioxide. With regard to the efficiency of the process in terms of biological stabilization of the mixture of biodegradable waste fed, the average removal of the volatile solids content fed was approximately 30%.