For soy biodiesel the generally agreed number is 3.2, that is, the fuel yields 3.2 times the amount of energy used to make it.
The table below is a break down of energy inputs:
|Production of rapeseed oil||57%||16356||51.7|
|Plant construction & maintenance||1%||162||0.5|
For WVO biodiesel, we get to eliminate at least the first item, production. Using the other energy inputs, this yields an ERoEI of 5.26, which is my working number at this time. If one were to collect the WVO with a biodiesel operated truck, and use biofuels for the operation of the processing plant, distribution, etc, this number could be somewhat higher.