It looks like they have boilers, ductable heaters, shop heaters, etc.
They are supposed to run on "Waste Oils":
What waste oil is acceptable to burn? Reznor Waste Oil Heaters and Boilers are designed for combustion of typical Crankcase Oils, Transmission Fluids, Hydraulic Fluids and # 2 Heating Oil, in any combination up to SAE-50 wt. Typical waste oils contain approximately 140,000 BTUs per gallon. No hazardous materials should be burned in the heater. Any mixture of these may be included in the same fuel tank. If you have questions regarding the suitability of a fuel, the factory should be consulted.
No specific notes on Veggie Oil or Biodiesel. However, the notes indicate that it can burn crankcase oil as cleanly as other systems burn #2 Diesel or Home Heating Oil.