Fig. 2. (Bio)molecules enhance heat-driven CH₄ formation.

a Overview of CH₄ formation driven by heat. Living organisms produce S-/N-methylated compounds that serve as substrates for CH₄ formation and Fe²⁺-chelators that promote Fenton chemistry and enhance CH₄ formation. b Heat-driven CH₄ (upper panel) and C₂H₆ (lower panel) formation is enhanced upon supplementation with (bio)molecules. c Citrate enhances heat-driven CH₄ formation acting as iron-chelator. Upon the addition of Ca²⁺, CH₄ levels decrease due to the replacement of Fenton-promoting Fe²⁺-citrate complexes with Ca²⁺-citrate complexes. All experiments were conducted in closed glass vials containing a buffered solution (pH 7) supplemented with DMSO, Fe²⁺ and, optionally, citrate and Ca²⁺ under a pure nitrogen atmosphere at 97 °C (heat). Statistical analysis was performed using paired two-tailed t tests, *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001. The bars are the mean + standard deviation of triplicates, shown as circles. a Was created with BioRender.com.