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.