NOVELTY - An anaerobic digestion system (100) comprises a clarifier (300) for receiving a first biomaterial and a second biomaterial and undertaking pretreatment processing of the first and second biomaterials to form a digestate; a batch reactor (400) coupled to the clarifier, where the batch reactor comprises chambers in fluid communication with each other providing for the flow of the digestate through it, and a digestion substrate disposed within the chambers; and a digester (500) coupled to the batch reactor configured to receive the digestate from it.    USE - As anaerobic digestion system for performing anaerobic digestion of biomaterials (claimed); and for processing and treatment of primarily organic waste to produce non-hazardous, and sometimes beneficial products.    ADVANTAGE - The anaerobic digestion system is more efficient. The clarifier for pretreatment processing of biomaterials improves anaerobic digestion.    DETAILED DESCRIPTION - An anaerobic digestion system (100) comprises a clarifier (300) for receiving a first biomaterial and a second biomaterial and undertaking pretreatment processing of the first and second biomaterials to form a digestate; a batch reactor (400) coupled to the clarifier, where the batch reactor comprises chambers in fluid communication with each other providing for the flow of the digestate through it, and a digestion substrate disposed within the chambers; and a digester (500) coupled to the batch reactor configured to receive the digestate from it. Each of the clarifier, the batch reactor, and the digester, comprises at least one gas sample port configured to withdraw gas from it. The anaerobic digestion system further comprises a gas and mass flow control assembly configured to control a flow of gases and the digestate between the clarifier, the batch reactor, and the digester based on the gas analysis data. The first biomaterial comprises a chemical oxygen demand per liter of 1-3000 g and volatile solids content per liter of 1-200 g. The second biomaterial comprises organic volatile solids and the second biomaterial is loaded into the clarifier at a rate of 0.01-250 g of volatile solids per liter-day. The system further comprises at least one biological reactor (350, 360) comprising at least one microorganism selected from hydrolytic microorganism and an acidogenic microorganism, where the at least one biological reactor is configured to supply the at least one microorganism to the clarifier. The batch reactor comprises at least one acetogenic microorganism. The digester comprises at least one methanogenic microorganism. An INDEPENDENT CLAIM is included for a method for anaerobic digestion involving receiving a first biomaterial and a second biomaterial into a clarifier; selectively undertaking pretreatment processing of the first and second biomaterials within the clarifier to form a digestate; passing the digestate through a batch reactor comprising a digestion substrate disposed in chambers that are in fluid communication with each other; transferring the digestate from the batch reactor to a digester; removing at least one gas generated during anaerobic digestion within the clarifier, the batch reactor or the digester; and supplying the at least one gas to the digester. The digestion substrate comprises at least one acetogenic microorganism.    DESCRIPTION OF DRAWING(S) - The figure shows schematic diagram of an anaerobic digestion system.    Anaerobic digestion system (100)    Influent collection tank (200)    Clarifier (300)    Biological reactors (350, 360)    Batch reactor (400)    Digester (500)