TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The biogas generator further comprises: an outflow conduit through which the slurry exits out of the reservoir; an overflow conduit where a terminal end of the overflow conduit inside the reservoir is positioned above a top level of the liquefied organic material as defined by a predetermined volume so that the liquefied organic material spills into the overflow conduit in response to the liquefied organic material exceeding the predetermined volume; a thermal sensor located in the reservoir for monitoring a temperature of the liquefied organic material during the anaerobic digestion process and for sending corresponding signals to a temperature control unit associated with the second pump, where in response to receiving the signals, the temperature control unit directs the second pump to vary the flow of the liquid through the heat exchanger in order to increase or to decrease the temperature of the liquefied organic material; a lid shaped to mate with the top of the reservoir and comprising many wheels and at least one agitators fixedly attached to an underside of the lid; a rigid annular support fixedly attached to the interior of the reservoir to support the lid and comprising a surface on which many wheels rests when the lid is placed on the reservoir; a handle fixedly attached to an outer surface of the lid and comprising a member that extends into a pump mechanism, where the pump mechanism places a force on the member thus causing the lid to rotate on many wheels and causing at least one agitator to move through the liquefied organic material in the reservoir to agitate the liquefied organic material; and at least one annular seal between the lid and the tank to prevent undesirable venting of foul odors from the liquefied organic material. The slurry exits out of the reservoir through the inflow conduit. The solar cells are electrically connected to a re-chargeable power source and the solar cells convert the solar energy into direct current electricity used to recharge the re-chargeable power source and the re-chargeable power source is connected to provide power to the first and second pumps. The lid is sized to rest on top of the reservoir with a peripheral edge of the lid inside the tank, where the peripheral edge extends into the liquefied organic material. The reservoir is substantially circular in shape and the rigid annular support is fixedly attached to the interior circumference of the reservoir. The wheels allow a user to rotate the lid manually to agitate the liquefied organic material in the reservoir. The agitators are elongated and extend downwardly from the lid. Preferred Method: The method further comprises agitating the liquefied organic material in the reservoir. The step of agitating comprises placing a force on a member of a handle fixedly attached to an outer surface of a lid shaped to mate the top of the reservoir, where the lid comprises many wheels and at least one agitator fixedly attached to an underside of the lid, the wheels are rest on a flat surface of a rigid annular support fixedly attached to the interior of the reservoir to support the lid, and the force on the member causes the lid to rotate on many wheels and causes at least one agitator to move through the liquefied organic material in the reservoir.