if it runs on animal fat
it will run on other hydro carbon fuels too.
Like any other diesel engine, it doesn't have to be fueled processed black oil.
I doubt that fueling warships with dead cows is the main goal of this project, if it is then crikey, that's morbid.
The option to put peanut oil, dead cow oil, sun flower oil, rapeseed oil or even black gold into the tank is a good move.