Methane production from wheat straw with anaerobic sludge by heme supplementation

• A cost-effective method of anaerobic digestion to produce methane was created.
• Heme was added in the anaerobic digestion process can improve methane production.
• Heme can improve reduce power of the whole fermentation system.
• The mechanism of heme as electron carriers was discussed.

Wheat straw particles were directly used as substrate for batch anaerobic digestion with anaerobic sludge under 35 °C to evaluate the effects of adding heme on methane production. When 1 mg/l heme was added to the fermentation process with no agitated speed, a maximum cumulative methane production of 12227.8 ml was obtained with cumulative methane yield of wheat straw was 257.4 ml/g-TS (total solid), which was increased by 20.6% compared with 213.5 ml/g-TS of no heme was added in the reactor. Meanwhile, oxido-reduction potential (ORP) level was decreased, the activity of coenzyme F420 was significantly improved and NADH/NAD+ ratio were the highest than other experimental groups. These results suggest that heme-supplemented anaerobic sludge with no agitated speed may be providing a more reductive environment, which is a cost-effective method of anaerobic digestion from biomass waste to produce methane with less energy consuming.