Biodiesel is a fuel made from recycled animal fats and oils, old restaurant grease (cooking oils) etc. I'd be very surprised if it would work in a cold model diesel engine though where the ether is needed to get ignition. It may work (and I'm just guessing) if the engine was started on normal fuel, allowed to warm up and then the fuel supply switched to the biodiesel.
This sort of system was once used in petrol tractors (when petrol was rationed) by starting on petrol, warming up the engine then switching over to kerosene.