You are looking it from the wrong angle the way I see it.

First there are significant quantities of oils grown used in cooking and discarded, in an often environmentally damaging way.

Reclaiming and burning these adds value to a waste product.

What is the EROI on batteries surely under 1.

These oils can provide energy storage and transmission in applications where electricity is ill suited, jet engines (coconut oil is especially suitable for this) and shipping come to mind.