A bioenergy management system and method for generating and supplying on-demand auxiliary electrical power is disclosed. The system/method includes a biogas generation unit (BGU) that produces biogas from dairy farm manure and stores the biogas in a biogas storage unit (BSU). An stored energy electric generation unit (SEGU) converts the stored biogas to electricity. A biogas control unit (BCU) measures the quality and quantity of biogas stored in the BSU and calculates available electric power (AEP) from this information. Depending on auxiliary electrical power requirements, a utility control unit (UCU) initiates an on-demand request for electric power (REP) to the BCU using a producer communication device (PCD)/utility communication device (UCD) data link. The BCU processes the REP from the UCU and negotiates electrical power (NEP) quantity. The BCU may electrically connect the SEGU to an electric transmission grid (ETG) to allow instantaneous/scheduled NEP delivery to the ETG.