Biogenic Carbon Fraction of Biogas and Natural Gas Fuel Mixtures Determined with¹⁴C

Abstract

This study investigates the accuracy of the radiocarbon-based calculation of the biogenic carbon fraction for different biogas and biofossil gas mixtures. The focus is on the uncertainty in the 14 C reference values for 100% biogenic carbon and on the 13 C-based isotope fractionation correction of the measured 14 C values. The separately (AMS) measured CO 2 and CH 4 fractions of 8 different biogas samples showed 14 C values between 102‰ and 116% (pMC). The δ 13 C values of these samples varied between -6‰ and +31‰ for the CO 2 fraction and between -28‰ and -62‰ for the CH 4 fraction. The uncertainty in calculated biogenic carbon fractions due to uncertainty in the 14 C reference values depends on the available information about the origin of the used biogenic materials. It varies between ±0.5% and ±3.5% (absolute) depending on the type of biogas. A method is proposed to minimize this uncertainty for different groups of biogases. The calculated biogenic carbon fraction deviates up to ±2.5% for biofossil gas mixtures, if the applied isotope fractionation correction is based on the δ 13 C value of the mixed biofossil sample instead of the biogenic δ 13 C value. Combination of both error sources shows that the uncertainty in the calculated biogenic carbon fraction varies between ±0.7% and ±4.5%, depending on the type of biogas in the sample.

Retrogressive thaw slumps temper dissolved organic carbon delivery to streams of the Peel Plateau, NWT, Canada

“…The radiocarbon signature of DOC was measured following extraction and purification at the A.E. Lalonde AMS facility (University of Toronto) using a 3MV tandem accelerator mass spectrometer (High Voltage Engineering) following established methodologies (Lang et al, 2016;Palstra and Meijer, 2014;Zhou et al, 2015), and is reported with an error estimate of 1σ .…”

“…Statistical analyses were completed in R version 3.1.3 (R Core Team, 2015) using the packages "nlme" (Pinheiro et al, 2015), "lmtest" (Zeileis and Hothorn, 2002), "lmSupport" (Curtin, 2015), "car" (Fox and Weisberg, 2011), and "zoo" (Zeileis and Grothendieck, 2005). The effect of slumping on stream chemistry and optical characteristics was assessed using linear mixed-effects models in the "nlme" package of R. For each parameter, analyses were split into two separate models that included data for upstream and downstream chemistry and upstream and within-slump chemistry.…”

Bringing AMS radiocarbon into the Anthropocene: Potential and drawbacks in the determination of the bio-fraction in industrial emissions and in carbon-based products

“…(1), expresses the 14 C content in the analysed material as refereed to a standard (IAEA C6 in our case) corrected for background, isotopic mass fractionation and for the radioactive decay of the calibration material e k t 0 Àts ð Þ term À Á . A detailed discussion about the use of the previous formula is also report in [23].…”

Efeito de reservatório marinho na costa do Brasil

“…Em estudos de fração biogênica de polímeros e combustíveis (Jou et al 2015, Palstra & Meijer 2014, por exemplo, não é necessário calibrar os resultados, mas sim determinar o percentual de carbono biogênico a partir do resultado de "fração moderna" (Stuiver & Polach 1977) fornecido pelo laboratório. Na maior parte das aplicações, no entanto, é fundamental proceder à calibração das idades de radiocarbono utilizando a curva apropriada.…”