Concern regarding the climate consequences of recent increases in the atmospheric CH₄ mixing ratio has focused research on the Earth's present-day atmospheric CH₄ budget. The Earth's CH₄ budget is based on constraints involving the atmospheric burden, residence times, and isotope composition of atmospheric CH₄. The atmospheric CH₄ budget (actually a net emission budget nearly balanced by photochemical oxidation) provides no information on processes that consume CH₄ before emission to the atmosphere. Predicting changes in source and sink terms under different conditions requires a focus on the gross global CH₄ budget. Global gross production of CH₄ is the quantity of CH₄ entering the atmosphere (net emission) plus global CH₄ oxidation (photochemical and microbial); it has been estimated by adding estimated and measured oxidation to each of the budget source terms. There appears to be no way to directly estimate the early Earth's atmospheric CH₄ mixing ratio, but the young Earth's CH₄ budget can be approached by adjusting source and sink terms to conditions estimated to exist then. Early Earth CH₄ sources are expected to be fewer and smaller than present-day sources. Photosynthetic primary production was likely smaller than present and occurred in bacterial mats bathed in shallow fresh and saline waters. Terrestrial primary production by vascular plants was absent, so the large wetland and rice production source terms for CH₄ were missing. Source terms involving anthropogenic activities (landfills, enteric fermentation, gas and oil production) were also absent. Provided sufficient organic matter was present, the tectonic processes that appear to lead to present-day CH₄ clathrate formation may have been active. The major present-day CH₄ sink, photochemical oxidation by the OH radical, was apparently active in a low-oxygen atmosphere. Wayne suggests that atmospheric lifetimes were about 5-fold longer than the present-day lifetime of 10 y. Carbon isotope evidence suggests widespread methanotrophy during early Earth history. Studies of methanotroph physiology may place bounds on the CH₄ concentration in some early Earth environments, but not necessarily the atmosphere. Methanogenesis and methanotrophy are closely coupled and consume a major fraction (~50%) of the CH₄ produced before emission to the atmosphere. Microbially-mediated CH₄ oxidation reactions on the young Earth could have been similar to those observed under present-day conditions. However, under the low-oxygen and low-sulfate conditions presumed for the young Earth, they may have been a less effective barrier to CH₄ emission.