Last year for the first time one issue of the journal Thermal Science was dedicated to internal combustion engines, as research of thermal processes taking place in this field are of interest to scientists. This was confirmed by the large number of submissions to this journal in the meantime in this field. Therefore, we have decided to dedicate another issue of the journal Thermal Science to the problem of IC engine thermal processes, with special attention paid on the application of alternative fuels. Solving problems of providing sufficient amounts of fuel for transport needs and emission reduction were the subject of many activities in the world. Solving these problems is important as all predictions show that the number of vehicles will grow in the following period. Emission reduction from traffic should be analyzed together with reducing greenhouse gas emission in accordance with the Kyoto Protocol. As a result of these activities in June 2009 the European Union replaced the 2003/30/EC Directive with the 2009/28/EC Directive, referring to promoting the use of energy from renewable sources. According to the new Directive, EU members are obliged to provide at least 10% of the total fuel amount from renewable sources by 2020. Additionally, biofuel, as the most significant renewable energy source must comply with the sustainability criterion and a methodology for calculating its influence on the greenhouse gas emission was precisely defined.