Fig. 2

Cumulative CH₄ production from H₂. α-cellulose (0.3 g) was added as substrate at the start of the experiment. H₂ was injected into the reactor headspace daily, following flushing with N₂. Green: no H₂ added, red: 0.79 mmol H₂ day⁻¹, black 1.57 mmol H₂ day⁻¹, blue: 2.36 mmol H₂ day⁻¹ added