Enhanced\nRock Weathering as a Source of Metals to\nPromote Methanogenesis and Counteract CO<sub>2</sub> Sequestration

Enhanced\nweathering of (ultra)mafic rocks has been proposed as\na promising approach to sequester atmospheric CO<sub>2</sub> and mitigate\nclimate change. However, these silicate rocks contain varying amounts\nof trace metals, which are essential cofactors of metallaenzymes in\nmethanogens. We found that weathering of crushed peridotite and basalt\nsignificantly promoted the growth and methanogenesis of a model methanogenMethanosarcina acetivorans C2A under the condition\nof excess substrate. The released trace metals from peridotite and\nbasalt, especially Fe, Ni, and Co, accounted for the promotion effect.\nObservation at different spatial scales showed a close association\nbetween the rocks and cells. Proteomic analysis revealed that rock\namendment significantly enhanced the expression of core metalloenzymes\nin the methylotrophic methanogenesis pathway. Our study uncovers a\npreviously unrecognized but important negative effect of enhanced\nrock weathering on methane production, which may counteract the carbon\nsequestration effort.