Biomass Carbon-14 Ratio Measured by Accelerator Mass Spectrometry

Abstract

Measurement methods of a biomass carbon ratio in biomass products based on ¹⁴C-radiocarbon concentration have been reviewed. Determination of the biomass carbon ratio in biomass products is important to secure the reliance in the commercial market, because the "biomass products" could contain products from petroleum. The biomass carbon ratio can be determined from percent Modern Carbon(pMC) using ASTM D6866 methods. The pMC value is calculated from the comparison between the ¹⁴C in sample and ¹⁴C in reference material. The ¹⁴C concentration in chemical products can be measured by liquid scintillation counter(LSC) and accelerator mass spectrometry(AMS). LSC can be applicable to determine the biomass carbon ratio for liquid samples such as gasoline with bioethanol(E5 or E10). On the other hand, AMS can be used to determine the biomass carbon ratio for almost all kinds of organic and inorganic compounds such as starch, cellulose, ethanol, gasoline, or polymer composite with inorganic fillers. AMS can accept the gaseous and solid samples. The graphite derived from samples included in solid phase is measured by AMS. The biomass carbon of samples derived from wood were higher than 100% due to the effect of atomic bomb test in the atmosphere around 1950 which caused the artificial ¹⁴C injection. Exact calculation methods of the biomass carbon ratio from pMC will be required for the international standard(ISO standard).