TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Component: There are 2-6, preferably 5 bioreactors and each is thermostatically controlled.Preferred Function: The bioreactor agitates the waste material to maintain the waste material as a suspension.    TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Condition: The pH of the waste material is monitored during, and lowered, when the waste material passes through the bioreactor system, only when the pH is not maintained below 4.9 for at least 24 hours. The pH is lowered by the addition of a strong mineral acid (1-10, preferably 10 mL) to the waste material. A base (5-25 mL/L of waste) is added to the bioreactor system after the addition of acid to elevate the pH of the waste material to 7.0-8.0. The bioreactor is heated to 25-40, preferably 30-40 degrees C. The waste material is retained in each bioreactor for 12-48, preferably 24 hours. The average dry weight of the waste material discharged into the bioreactor system is 3.5-8.5, preferably 4.0% dry weight.Preferred Parameter: The pH of a first bioreactor (19, 21, 23, 25, 27) is maintained at 4.8-5.5, preferably 5.0. The pH of a second bioreactor is maintained at 3.6-4.9, preferably 4.3.Preferred Method: The aeration takes place in a tank (14A, 14B, 14C) having a submersible sparger in which air is fed in the tank under pressure. An emulsifier is added to the waste material in the bioreactor system to produce an emulsion of triglyceride droplets in the waste material which is substantially in liquid form. Faeces (5-100, preferably 30-45 g wet wt/1000 L of waste material) are added to the waste material in the bioreactor system, and a second injection of faeces is added to the bioreactor system.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Compound: The strong mineral acid comprises hydrochloric acid, sulfuric acid or nitric acid.Preferred Component: Nitrogen, sulfur, carbon, phosphorus, potassium, magnesium, calcium, sodium, chlorine ion, and ammonium hydroxide (0.5-5.0, preferably 2.0 mL/L) are added to the waste material in the bioreactor system to facilitate oxidation of volatile fatty acids to carbon dioxide and water.Preferred Parameter: The amount of dissolved oxygen in each bioreactor is less than 0.7 mg/L.    TECHNOLOGY FOCUS - BIOLOGY - Preferred Component: Lipolytic bacteria, proteolytic bacteria or saccharolytic bacteria are added to the waste material in the bioreactor system.    TECHNOLOGY FOCUS - AGRICULTURE - Preferred Component: Agricultural fertilizer is added to the waste material in the bioreactor system.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: Readily fermentable carbohydrate, and waste of molasses (2-12, preferably 7 mL/L) are added to the waste material in the bioreactor system. EXAMPLE - A feed 5.44 dry weight % w/v. In the bioreactor, these amounts had decreased to 3.77 dry weight % w/v. The results with respect to biochemical oxygen demand of the sludge and water in the final reactor were 1545 mg/L. The amount of volatile fatty acids in the first, second and last aerator were 79, 33 and 31, respectively.