Kai thought about using the elemental energy to maintain his body like divine realm cultivators.
A divine realm cultivator didn't need to take food or water for them to stay active; they absorbed the Qi in the surroundings.
But the real reason they can live without food is that they are absorbing the elemental energy with the addition of Qi.
They can't directly absorb elemental energy like how Kai does using the Will Power; instead, Qi mixes elemental energy.
The elemental energy contains all the proteins and vitamins that are required by the body since the food we eat is indirectly created from them.
'Let's try this method' Kai decided to use this method since it wasn't risky, and he has used it for a long time.
The surrounding elemental energy started gathering near Kai, and it was absorbed into his body.
Kai didn't absorb them directly; instead, he used his Will Power to extract the components from them.