Determination of the renewable energy content of chemically modified biofuels

The recent EU directive on renewable energy sources (Directive 2009/28/EC) promotes the use of biofuel and bioliquids that could be produced through chemical processes. These biofuels consist of a biogenic (renewable) part and a non-renewable (fossil or non-biogenic) part. A method to evaluate the renewable and non-renewable energy fractions released during combustion is presented. The method is based on thermochemical criteria of bond dissociation energies and on the knowledge of the molecular structure of reagents and products. Its application to MTBE and ETBE analysis provided results that are close to those published in the directive. In particular, application of the method on these products points out a renewable fractions of 23.7% and 35.9% compared with the 22% and 37% listed by the RED. Moreover, the application of the method to products of the process production of FAME with use of fossil methanol, shows a fraction of non-renewable energy very low. For glycerol this value is 1.6% and for the methyl ester fraction of non-renewable energy depends on the type of molecule but always less than 2.4%. These findings could be used to devise correction criteria for the fiscal mechanisms being applied to these biofuels.