Like Joe Biden, Amtrak now runs on beef tallow. America's rail company just replaced 35,000 gallons of diesel fuel in one of its 3,200-horsepower locomotives with biofuel derived from the stuff, and reports that the experiment resulted in no ill effects for the train, and lower than usual emissions.
That doesn't mean using beef-based biofuels is a good idea — even conventional plant-based biodiesel is only somewhat better than fossil fuels from the standpoint of carbon and other environmental impacts. Running all those calories through a cow first is just kinda dumb.
But hey, if there's tallow lying around that isn't already being used to cause millions of heart attacks, who am I to argue with using every part of the buffalo… er, cow.