There might be a problem here, modern diesel engines have had 100 years of development, as have fuels, but very small engines with their poor breathing and simple fuels have not.
As I understand it (I am not a user of these engines) the fuel contains ether which self-ignites on compression and sets the rest of the fuel off, which consists of petrol and paraffin, and vegetable oil for lubrication. Maybe nowadays the castor oil is replaced by synthetic oil.
Of these, only the vegetable oil is naturally based, the rest are more or less chemically manufactured.
Diesel oil for cars and trucks is often only about 15% bio-fuel, and refined and filtered chip oil, whilst often naturally obtained from seeds, is not environmentally friendly, as it results from square miles of tropical rainforest being cleared for palm oil plantations.
Regards
Geoff