Breathing Planet Earth: Analysis of Keeling’s Data on CO2 and O2 with Respiratory Quotient (RQ), Part I: Global Respiratory Quotient (RQGlob) of Earth

Abstract

In biology, respiratory quotient (RQ) is defined as the ratio of CO2 moles produced per mole of oxygen consumed. Recently, Annamalai et al. applied the RQ concept to engineering literature to show that CO2 emission in Giga Tons per Exa J of energy = 0.1 ∗ RQ. Hence, the RQ is a measure of CO2 released per unit of energy released during combustion. Power plants on earth use a mix of fossil fuels (FF), and the RQ of the mix is estimated as 0.75. Keeling’s data on CO2 and O2 concentrations in the atmosphere (abbreviated as atm., 1991–2018) are used to determine the average RQGlob of earth as 0.47, indicating that 0.47 “net” moles of CO2 are added to which means that there is a net loss of 5.6 kg C(s) from earth per mole of O2 depleted in the absence of sequestration, or the mass loss rate of earth is estimated at 4.3 GT per year. Based on recent literature on the earth’s tilt and the amount of water pumped, it is speculated that there could be an additional tilt of 2.7 cm over the next 17 years. While RQ of FF, or biomass, is a property, RQGlob is not. It is shown that the lower the RQGlob, the higher the acidity of oceans, the lesser the CO2 addition to atm, and the lower the earth’s mass loss. Keeling’s saw-tooth pattern of O2 is predicted from known CO2 data and RQGlob. In Part II, the RQ concept is expanded to define energy-based RQGlob,En, and adopt the CO2 and O2 balance equations, which are then used in developing the explicit relations for CO2 distribution amongst atm., land, and ocean, and the RQ-based results are validated with results from more detailed literature models for the period 1991–2018.