engleski

DETERMINATION OF BIOGENIC FRACTION IN USED CAR TYRES AND IN LIQUID FUELS BY 14C METHOD

Intensive use of fossil fuels for energy production and transport during 20th century caused an increase of CO2 concentration in the atmosphere. The increase of CO2 concentration can be slowed down by the use of biogenic materials for energy production and/or transport. One of the method for determination of the fraction of the biogenic component in any type of fuel or waste is the 14C method, which is based on different content of 14C in biogenic and in fossil component: while the biogenic component reflects the modern atmospheric 14C activity, no 14C is present in fossil fuels. The 14C method is the most reliable method of determination of the biogenic fraction in various materials. It can be applied to various types of fuels used, such as solid communal waste, used car tyres, liquid fuels, even to the CO2 produced by combustion of various fuels. Any measuring technique used in 14C laboratories could be used. Here we present comparison of characteristics (precision, complexity, and price) of various techniques for biogenic fraction determination by the 14C method in used car tyres, based on our experience. Determination of biogenic fraction in liquid fuels is of special interest because all (liquid) fuels have to contain at least 10 % of bio-fuel, i.e., blend of biogenic origin, by 2020 (EU Directive 2009/28/EC). A technique of direct measurement of the 14C content in liquid fuel is simple and fast but has a main disadvantage: different liquid colours cause different quenching properties and changes in the measurement efficiency. Various methods have been suggested to overcome this problem (e.g., decolourization, separate quenching curves for various combinations of the fossil matrix and biogenic blends). We have proposed a new technique that uses liquids of different colours to construct modern and background calibration curves. The technique depends neither on the fossil matrix or the biogenic additive type. Lowest detectable biogenic fraction is 0.5 %. A case/problem of highly quenched samples still remains to be solved.

14C; biogenic component; car tyres; liquid fuels

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