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The 14C method can be successfully applied for determination of biogenic component in any type of samples and different measurement techniques can be applied. For a special case of liquid fuels, direct method by measurement 14C activity of liquid fuel samples in liquid scintillation counter (the „direct LSC method“) has been recognized as a powerful and reliable method of determination of biogenic component (fbio). In the Ruđer Bošković Institute (RBI) Radiocarbon Laboratory we have been implemented our own data evaluation method based on the quench properties of fuels (SQP(E) – Standard Quench Parameter in LSC Quantulus 1220) [1]. We participated in the international intercomparison study ILC/2018 Content of biocomponent in liquid fuel samples, which was organized in 2018 by the Institute of Ceramics and Building Materials (Opole, Poland). Here we compare our fbio results with the fbio-ILC official results and report optimization of the direct LSC method. Laboratories obtained seven samples of diesel type of fuel having different colors. Consequently, the samples resulted in different SQP(E) values when the direct LSC methods was applied. Three samples were analyzed by the AMS (Accelerator Mass Spectrometry) method. The LSC results were quantitatively acceptable for four samples with SQP(E) values above 700 (Figure 1), which was taken as the lowest limit of quantitative fbio determination. Qualitatively acceptable, but quantitatively unacceptable results, were obtained for two samples with the SQP(E) values between 600 and 700, that was defined as the region of limited applicability. For one of the samples the quenching was high, SQP(E) < 600, and the direct LSC method did not give any result. However, all AMS results were acceptable (Figure 1) since AMS does not depend on the sample color. The obtained results have been used for further validation and optimization of the direct LSC method. We defined the limits of applicability of the direct-LSC method for both quantitative (SQP(E) > 700) and qualitative results (600 < SQP(E) < 700). A sample of used edible oil (UEO, laboratory code Z-7226) was used to test these limits. The UEO was a dark sample giving the SQP(E) value of 546 (below the limit of qualitative applicability), while the AMS revealed fbio = 97.9 ± 0.3 % (and δ13C = -29.6 ‰). We mixed the UEO with the (fossil) petrol (benzene) sample (laboratory code Z-6266), which we used as the background sample (fbio = 0 %) with good quenching properties (SQP(E) = 864). We monitored changes in the SQP(E) and fbio values in UEO-petrol mixtures in the concentration range 0 – 100 %. The total mixture volume was 10 mL and 10 mL of Ultima Gold F scintillation cocktail was added, i.e., the measurement was performed in the same manner as all other organic liquid samples [1]. Mixtures of 10 % and 20 % of UEO gave SQP(E) values of 773 and 759, and the fbio was calculated to be 104.0 ± 1.2 % and 101.1 ± 1.3 %, respectively, confirming the quantitative region of SQP(E) values above 700. Mixtures containing 30 – 50 % of UEO resulted in SQP(E) values between 671 and 609, while the fbio values were about 150 %, confirming qualitatively acceptable results. Mixtures containing more than 60 % of UEO had SQP values below 600 and fbio values had a large spread. The presented results showed that the direct LSC method with an evaluation method developed in our laboratory was suitable for determination of the fbio in liquid fuels, providing the correctly defined limits of applicability for highly quenched samples. The RBI Laboratory has a possibility of applying also AMS 14C measurement technique that can satisfactorily determine fbio also in highly quenched samples, but the AMS technique is more complicated and more expensive.

The study aims to get some additional knowledge on the modern seafloor composition offshore Brunei Darussalam by looking at the recent stratigraphic succession of the deposited sediments and their distribution patterns. For this reason, 10 shallow cores (22 to 46 cm thick) have been collected by scuba diving along two depth transects spanning from water depth of 20 to 60 m. One of the transects has been sampled north-northwest of the Muara village, just in front of the Brunei Bay and the other one off the coast near Tutong town, away from major sedimentary inputs. The results obtained portray two different sea bottom compositions and two different depth-related sediment distributions. The Muara transect is highly rich in mud and yielded abundant biogenic component at all investigated depths. The Tutong transect has a higher sand content but display constant changes along with depth. The sediment is mostly composed by biogenic grains such as rests of sponges, foraminifera, molluscs and echinoderms; the not biogenic grains are for the vast majority made of quartz. The sandy fractions of both transects have been tested for cyclicity and all cores can be described by functions with comparable periods, thus indicating that an oscillatory environmental event such as the alternation of the monsoon seasons, has similar influence on the seafloor of both transects.

Biogenic component in solid and liquids can be determined by the 14C method - the biogenic component has the 14C activity of the contemporary atmosphere, while fossil component does not cantain any 14C. For liquid fuels iz is possible to apply also the direct method by measuring 14C activity by liquid scintillation counters. However, the direct LSC method has some limitations of applicability. Here we discuss the applicability of the direct LSC method for coloured liquid fuels, and also compare the direct LSC with the AMS method.

The 14C method can be successfully applied for determination of biogenic component in any type of samples. For a special case of liquid fuels, the „direct LSC method“ for measurement 14C activity by a liquid scintillation counter (LSC) has been recognized as a powerful and reliable method of determination of biogenic component. Laboratories of the Ruđer Bošković Institute (RBI) in Zagreb, the Jožef Stefan Institute (JSI) in Ljubljana, and at the Faculty of Science of the University of Novi Sad (UNS) in Novi Sad implemented the direct LSC method and optimized slightly different measurement and evaluation procedures (Krajcar Bronić et al., 2017, Krištof and Kožar Logar, 2013, Stojković et al., 2017). They defined limits of applicability of the direct LSC method by the values of the Standard Quench Parameter SQP(E) determined by the LSC Quantulus 1220. The laboratories participated in the international inter-laboratory comparison study ILC/2018 „Content of biocomponent in liquid fuel samples“, which was organized in 2018 by the Institute of Ceramics and Building Materials (Opole, Poland). Here we present the results obtained by these 3 laboratories and compare the fbio results with the expected fbio-exp values. Seven samples of diesel type of fuel having different concentrations of biocomponent and different colours were obtained. The results for samples with the SQP(E) values well above the limits of applicability of the direct LSC method were satisfying in all three laboratories. Qualitatively acceptable, but quantitatively unacceptable results, were obtained for a sample in the SQP(E) region of limited applicability. One of the samples exhibited a high quench level, so the SQP(E) parameter was below the limits of applicability of the direct LSC method in all 3 laboratories, (SQP(E) < 600). The RBI laboratory applied accelerator mass spectrometry (AMS) technique to determine fbio in this highly-quenched sample as well as in the sample without 14C (SQP(E) > 800) and in the sample having SQP(E) in the limited region of applicability (600 < SQP(E) < 700). The JSI laboratory applied the direct absorption of CO2 in an absorption-scintillation cocktail (DA) technique for the highly-quenched sample (SQP(E) < 600). The UNS laboratory used the biogenic oil for calibration and also the internal standard method (IntSt), and the latter resulted in better agreement with the expected values. Although there were some differences in details of the applied direct LSC methods in the three laboratories, the presented intercomparison results showed that all the methods were suitable for determination of the fbio in liquid fuels, providing the correctly defined limits of applicability for highly quenched samples. Laboratories that have possibility of applying a different 14C measurement technique can satisfactorily determine fbio also in highly quenched samples.

Biogenic materials itself or as blends to fossil fuels are presently often used for energy production and/or transport. One of the methods for determination of the fraction of the biogenic component in any type of fuel 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. A technique of direct LSC measurement of the 14C content in liquid fuels is simple and fast because it does not require any sample pre-treatment. However, its main disadvantage is caused by different liquid colours that change quenching properties and measurement efficiency. Recently we proposed a new evaluation technique that takes advantage of different quenching properties of various liquids of different colours. By utilizing various modern organic liquids (various brands of domestic oils, benzene, ethylene) we constructed the modern calibration curve that relates their count rates and SQP (standard quench parameter) values. A background calibration curve was constructed by using various 14C-free liquids. All samples were prepared in low-potassium glass vials with the UltimaGold F scintillator (10 mL of a sample and 10 mL of UGF). Measurement was performed by LSC Quantulus 1220 and spectra were evaluated in the window 124 – 570 channels. We suggest that the data evaluation method could be used for determining the biogenic fraction in various types of organic liquids, including liquid fuels of unknown chemical composition. Here we present further studies of the applicability of the proposed method. We have prepared mixtures of fossil fuels and some biogenic liquids in a nominal concentration range of the biogenic component from 0 % to 100 %. Test will be made to check if the proposed method depends on the qualitative composition of the mixture, i.e., on the fossil matrix or the biogenic additive type. The sensitivity and limitations of the method will be discussed.

A method of direct measurement of14C activity concentration via liquid scintillation counting (LSC) is recognized as good and fast method for determination of biogenic component in liquid fuels. Two laboratories that used this14C technique participated in this survey: Laboratory from University of Novi Sad (UNS), Serbia and Laboratory from Ruđer Bošković Institute (RBI), Croatia. Each laboratory used its own calibration methods on the same set of samples (produced diesel-based bio-fuels and commercially available domestic oils). From the obtained results it can be concluded that each method which uses 14C technique for determination of biogenic component in liquid fuels has its advantages and disadvantages. RBI data evaluation method is based on two calibration curves, for purely biogenic and purely fossil liquids, and the calibration does not depend on the exact chemical composition of the organic liquid. The limits of the method are defined by the SQP(E) of approximately 690. Below this value the count rates of biogenic and fossil liquids become close to each other or even indistinguishable from one another and the obtained results for biogenic fractions are not reliable. In this intercomparison UNS used two different methods, one for produced bio-diesels and the other one for domestic oils. UNS data evaluation method is very dependent on the composition of the examined fuels, so the obtained results with the "two-step" method were relatively good in the case of diesel mixtures with biogenic component. In the case of biogenic oil samples (bought on market), UNS "two-step" method did not give realistic results, and with the "one-step" method the limitation is large quenching in the samples, so for the samples with SQP(E) less than 700 this method could not give expected results. Samples prepared with liquid fuels are usually colored and the main challenge for determination of biogenic component in both laboratories is handling of highly quenched liquids.

The fraction of biogenic component within various types of materials that can be used as fuels for energy production and transport can be determined by measuring their 14C activity. The method is based on different 14C signatures of the biogenic and the fossil components: while the biogenic component reflects the modern atmospheric 14C activity, no 14C is present in fossil fuels. A direct measurement of the 14C content in liquid fuel by liquid scintillation counter is a simple and fast technique but has a main disadvantage: different liquid colors cause different quenching properties and affect the measurement efficiency. We propose a new evaluation technique that uses liquids of different colors to construct modern and background calibration curves. Various binary mixtures of biogenic liquids have been used to verify the relation between the count rate and the quenching parameter. Mixtures of a biogenic and a 14C-free liquid demonstrated the potential of the proposed technique for determining the biogenic fraction of a mixture.

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 fuels and 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. A case of liquid fuels will be specially discussed. According to the EU Directive 2009/28/EC all (liquid) fuels have to contain at least 10 % of bio-fuel, i.e., blend of biogenic origin, by 2020. 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 propose here 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 %.

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.