NOVELTY - The method involves feeding a biological material to an infeed device (2) functioned as a sluice system. The pressure in the infeed device is increased. The biological material is transferred from the infeed device to a reactor (1) through a transfer pipe by pressure differences or gravity. The pressure in the reactor is increased. The biological material is subjected to steam injection in the transfer pipe. The reactor is operated at an elevated pressure in the range of 2 to 25 barg and operated at a temperature in the range of 110 to 240 degrees C.    USE - Method for continuous treatment of biological material used for production of biogas (claimed). Uses include but are not limited to agricultural product e.g. grass, sugar beet pulp, rice straw, rice hull, wheat straw and empty fruit bunch, forest product e.g. bark, wood chip, paper sludge, sawdust and hardwood, biological industrial waste and byproduct e.g. brewery and distillery, animal product e.g. meat waste and byproduct from slaughterhouse and dead animal, biological sludge e.g. wastewater treatment, industrial wastewater treatment and sediment, and farm waste and byproduct e.g. cattle manure, pig manure and deep bedding.    ADVANTAGE - By transferring the biological material from infeed device to reactor by pressure differences or gravity, the biogas can be manufactured in the uncomplicated and cost-effective manner. The energy required for heating the biological material can be reduced. The construction and maintenance cost of the reactor can be reduced. The need for high pressure pump for treatment of biological material can be eliminated. The temperature in the treated biological material can be reduced. The dry material content in the treated biological material can be increased. The amount of volatile compounds in the treated biological material can be reduced.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view illustrating the process for continuous treatment of biological material.    Reactor (1)    Infeed device (2)    Economizer (4)    Outlet valve (7)    Inlet valve (8)