Biogas digester tank heating method and system, and modular heating rack for the same

A biogas digester tank heating method, system and modular heating rack is provided. The method can include providing a digester tank having a base and a vertical wall surrounding the base. A plurality of heating racks can be provided, where each of the plurality of heating racks is a pre-assembled unit including a plurality of parallel pipes and a stand configured to secure the plurality of parallel pipes to the base of the biogas digester tank. The plurality of heating racks can be secured to the base, adjacent to the vertical wall. Each of the plurality of heating racks can be connected to a heating manifold arranged outside of the digester tank in parallel such that a heat exchange fluid is configured to independently flow from the heating manifold through the plurality of parallel pipes of each individual heating rack of the plurality of heating racks.