A density engine includes an object movably positioned in a host liquid, the object having a density less than that of host liquid. An injector injects gas below the object creating a rising fluid region having a density less than that of the object. The object is not buoyant in the rising fluid region. An electrical generator is coupled to the object to generate electrical energy upon movement of the object. A biofuel production facility receives gas from the density engine and produces a biofuel through a biological process of a living organism that utilizes the gas. A consolidated energy production and storage system includes a gas sequestration facility, a density engine, and a biofuel production facility located together on a contiguous plot of land. Windmills and solar collectors may be located on the plot of land.
