Renewable and CO2 – natural liquid fuels – biofuels such as vegetable oils, palm oils, coconut, sunflower and rape seed oils are today very appreciated in more and especially more European countries as the green energy sources for land and sea electrical power generation. The paper in the first part discusses the various controversial opinions on the rapidly growing production of vegetable oils for biodiesel production and the possibilities that this may cause higher food prices and spread famine in many countries. The second part of the paper highlights various technical issues of biofuels application on marine diesel engines. The pros and cons of biofuels application are given