Monthly carbon emissions from natural-gas flaring and cement manufacture in the United States

Abstract

Annual data on carbon emissions from fossil-fuel combustion and cement manufacture have been used in studies of the carbon cycle for the last few decades. However, annual data do not specify carbon emissions on the seasonal timescales relevant to biospheric uptake and other processes affecting the carbon cycle. Estimates of monthly emissions from fossil-fuel consumption in the United States (US) have shown that an increasing percentage of the annual emissions are occurring during the growing season; however, carbon emitted from flaring natural gas at well sites was not accounted for in those emissions estimates, nor was carbon emitted during cement manufacture. Here we show that emissions from flaring, which amount to around 0.1 % of all fossil-fuel carbon emissions in the US, have no clear and persistent annual pattern that can be detected in the data. In contrast, carbon emissions from cement manufacture, which add about 0.7% to carbon emissions from fossil fuels in the US, have a clear and persistent annual pattern including low values in late winter and early spring. In this paper, we provide a few remarks on carbon emissions from natural-gas flaring before presenting monthly emissions estimates. We then focus on the methodology for calculating carbon emissions from cement manufacture before presenting and discussing the monthly emissions estimates.