Axel Kleidon has provided this provocative attempt to construct a theory of power generation in the hierarchy of processes operating on our planet [1]. This paper reasserts the relevance of Maximum Entropy Principle. I look forward to a vigorous debate. I challenge his main conclusion that biology has dominated the geochemical power contribution to surface processes. First, his comparison of the computed biotic generation rate of chemical free energy, assuming conversion to sugar (the proxy for carbohydrates), to abiotic processes is misleading since most this biotically-derived free energy is in the form of wood, the inert support for terrestrial photosynthesis, which of course decays back to carbon dioxide and water. While this decay process does entail soil biotic activity, it pales in comparison to the energy inputs of solar energy to the water cycle, including weathering and mass transport in the carbon cycle, by a factor of 10 5 (see [1] and its referenced papers).
The proper control for assessing biotic influence is the inferred abiotic state of the Earth's surface system. A consideration of the abiotic long-term carbon cycle leads to the conclusion that life via its biotic enhancement of weathering (BEW) has brought the atmospheric carbon dioxide level closer, and not further, from equilibrium relative to an abiotic Earth without the catalytic BEW influence [2,3]. While life has driven atmospheric oxygen up, it has driven carbon dioxide down. Thus, I challenge Kleidon's argument that life necessarily drives systems progressively further from equilibrium, likewise his approval of Lovelock's proposal that atmospheric chemical disequilibrium is the "unmistakeable sign of a planet with widespread life". Abiotic steady-states far from equilibrium are also possible, e.g., abiotic flux of methane combined with oxygen from water photodissociation. The full astrophysical context, such as the star's radiative flux, must be considered to distinguish between abiotic and biotic far-from-equilibrium exoplanetary atmospheres.
Returning to the abiotic Earth control, the temperature gradient between its surface and the cold heat sink in space should be greater than the present surface, given the higher abiotic surface temperature, plausibly resulting in more vigorous convective processes in the atmosphere, and likewise more intense physical weathering and erosive processes than the present biotic surface. We have geochemical evidence that early Earth was likely more tectonically active than at present, despite a weaker biotic impact. This evidence points to vigorous plate tectonics and continent formation in the first 2 billion years of Earth history [4] even though biotic activity has been greatly magnified in the last 500 million years as a result of the rise of higher plants with its massive creation of free energy.