They must be buried, they contain so much carbon that to burn them all would make a big, and I mean big, dent in Earth's carbon cycle! All those big fat asses spent their lives as literal carbon vacuums, it is necessary that the carbon be returned other wise we will lose large amounts of essential chemicals.  Burning them for oil is a genuinely good idea, as hamplanets contain so much fat we could probably heat a house for an entire year on a single tumblrina, but it is better to return their Atlas sized bodies to the Earth so that they may be properly recycled.