Markku Oinonen, docent, Director of Laboratory & Antto Pesonen, Quality Coordinator

One of the most important ways to decrease greenhouse gases and to control the climate change is decreasing the use of fossil, non-renewable fuels. One of the ways to help in this is by increasing the use of biofuels, such as biodiesel and similar products. In order to verify the use of biobased fuel in a fuel mixture, the ratios of fossil and biofuel must be determined.

In very old fossil matter, i.e. mineral oil, the amount of radiocarbon (¹⁴C) is nonexistant. This is due to the radioactive disintegration combined with the half-life of radiocarbon (5730 years). In modern biological matter, however, the level of radiocarbon is the same as the level of radiocarbon in atmosphere. By determining the radiocarbon from a liquid fuel mixture or from the CO₂ gained from combusting the fuel, it is possible to calculate the ratios of biobased and fossil carbon in the fuel mixture.

The method is applicable to any material containing carbon and required amount of sample is very small when using Accelerator Mass Spectrometric (AMS) determination technique.

Laboratory of Chronology has developed new methods of determination in cooperation with VTT Technical Research Centre of Finland with the support of TEKES, the Finnish Funding Agency for Technology and Innovation. During the years 2005-2010 biofraction determinations of liquid fuel samples have been performed by so-called Closed-Tube-Combustion method (Oinonen et al 2010) described in official standards (ASTM 2012). In addition, Elemental Analyzer -based sample preparation method has been developed which is faster, more repeatable and more accurate. Cooperation in development of liquid fuel sample analytics is further developed with Finnish Customs Laboratory by international sample sets and EA-AMS method is taken into use also for other sample materials. Using a special sampling equipment developed by VTT it is possible to sample flue gases from power plants and determine the ratios of fossil fuels and biobased fuels using the same principle. Laboratory of Chronology is heading towards laboratory accreditation with the processes described.

ASTM D6866-12. Standard Test Methods for Determining the Biobased Content of Solid, Liquid, and Gaseous Samples Using Radiocarbon Analysis, ASTM D 6866 – 12, ASTM International, West Conshohocken, USA, 2012.

Hämäläinen KM, Jungner H, Antson O, Räsänen J, Tormonen K, Roine J (2007) Measurement of biocarbon in flue gases using ¹⁴C. Radiocarbon 49: 325–330.

Oinonen M, Hakanpää-Laitinen H, Hämäläinen K, Kaskela A, Jungner H (2010) Biofuel proportions in fuels by AMS radiocarbon method. Nucl. Instr. Meth. Phys. Res. B 268: 1117–1119.