NOVELTY - Processing biodegradable waste comprises providing at least one waste processing device, the or each device having a processing passage with a passage inlet and a passage outlet, and a nozzle circumscribing the passage and opening into the passage between the passage inlet and passage outlet; directing a flow of a biodegradable waste slurry into the processing passage; and supplying a processing fluid to the nozzle and injecting the processing fluid through the nozzle into the waste slurry within the processing passage.    USE - The methods are useful for processing biodegradable waste; and for producing biogas from biodegradable waste (all claimed).    ADVANTAGE - The methods provide high efficiency of quality biogas production.    DETAILED DESCRIPTION - Processing biodegradable waste comprises providing at least one waste processing device, the or each device having a processing passage with a passage inlet and a passage outlet, and a nozzle circumscribing the passage and opening into the passage between the passage inlet and passage outlet; directing a flow of a biodegradable waste slurry into the processing passage; and supplying a processing fluid to the nozzle and injecting the processing fluid through the nozzle into the waste slurry within the processing passage; where the processing fluid is supplied to the or each device at a temperature and pressure which results in the waste slurry leaving the passage outlet with an exit temperature of 45-160 degrees C. INDEPENDENT CLAIMS are included for:    (1) a method of producing biogas from biodegradable waste, comprising providing at least one waste processing device, the or each device having a processing passage with a passage inlet and a passage outlet, and a nozzle circumscribing the passage and opening into the passage between the passage inlet and passage outlet; directing a flow of a biodegradable waste slurry into the processing passage; and supplying a processing fluid to the nozzle and injecting the processing fluid through the nozzle into the waste slurry within the processing passage, where the processing fluid is supplied to the or each device at a temperature and pressure which results in the waste slurry leaving the passage outlet with an exit temperature of 45-160 degrees C; passing the processed slurry into a digester downstream of the or each device, the digester being configure to facilitate anaerobic digestion of the processed slurry; and recovering biogas generated in the digester; and    (2) a waste processing apparatus comprising at least one waste processing device, the or each device having a processing passage with a passage inlet and a passage outlet; and a nozzle circumscribing the passage and opening into the passage between the passage inlet and passage outlet; and a retention vessel downstream of the passage outlet, the retention vessel adapted to hold a waste slurry exiting the at least one device at an exit temperature and pressure for a predetermined period of time.