TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: In processing biodegradable waste, 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 95-130 degrees C. The nozzle of the or each device has a nozzle throat whose cross sectional area is less than that of both a nozzle inlet and a nozzle outlet, and where the processing fluid is accelerated through the nozzle throat as it is injected into the passage. The method further comprises holding the processed slurry at the exit temperature and an associated exit pressure in a retention vessel downstream of the passage outlet for a predetermined period of time. It also comprises passing the processed slurry from the retention vessel into a decompression vessel where the pressure of the slurry is rapidly reduced and any gaseous elements are drawn off from the slurry. It comprises 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. The processed slurry is passed through a forced cooling device located between the or each processing device and the digester, such that the slurry entering the digester has an entry temperature of 30-55 degrees C. The method further comprises introducing one or more chemical additives to the slurry before, during or after processing within the processing device. Each additive is selected from enzymes and chemical reagents. Producing biogas from biodegradable waste further comprises holding the processed slurry at the exit temperature in a retention vessel downstream of the passage outlet for a predetermined period of time prior to passing the slurry into the digester; and passing the processed slurry from the retention vessel into a decompression zone where the pressure of the slurry is rapidly reduced and any gaseous elements are drawn off from the slurry. The processed slurry is passed through a forced cooling device located between the or each processing device and the digester, such that the slurry entering the digester has an entry temperature of 30-55 degrees C. Preferred Apparatus: In the apparatus, the nozzle of the or each device has a nozzle throat whose cross sectional area is less than that of both a nozzle inlet and a nozzle outlet. The apparatus further comprises a decompression vessel downstream of the retention vessel; a digester; a forced cooling device located between the retention vessel and the digester; waste processing devices connected to one another in series; and a separate retention vessel downstream of each of the waste processing devices. At least one of the waste processing devices is located within the retention vessel of the preceding waste processing device. The apparatus also comprises an enzyme entrainment unit having a hopper adapted to hold and deliver one or more enzymes into the processing passage either upstream of, downstream of, or at the nozzle. EXAMPLE - No suitable example given.