Two-stage thermophilic anaerobic co-digestion of corn stover and cattle manure to enhance biomethane production

Abstract

Two-stage thermophilic anaerobic co-digestion of cattle manure and corn stover was conducted to increase biomethane production. The first stage pre-digestion of corn stover was studied based on the following treatment variables: corn stover to liquid fraction of digestate (CS:LFD) ratio (1:7, 1:10, 1:13, 1:14), digestion temperature (55 °C, 60 °C) and digestion time (3, 7, 14 days). The reduction in lignin, cellulose and hemicellulose (LCH) was between 3.97% and 11.98%, which increased the biodegradability of corn stover. Corn stover pre-digested with a CS:LFD ratio of 1:10 at 55 °C for a period of 3 and 7 days was subjected to anaerobic co-digestion with cattle manure. The highest biomethane yield was observed on day 21 with a value of 357.41 mL/g volatile solids (VS) for untreated corn stover, 446.84 mL/g VS for corn stover pre-digested for 3 days and 518.58 mL/g VS for corn stover pre-digested for 7 days with LFD. The VS conversion efficiency for co-digestion of cattle manure with untreated corn stover, corn stover pre-digested for 3 days and 7 days was 42.8%, 43.3% and 51.8%, respectively, on day 21, which was higher than that (34.0%) of cattle manure only.

Keywords:

• Anaerobic digestion
• co-digestion
• pre-digestion
• cattle manure
• corn stover
• liquid fraction of digestate
• thermophilic
• biomethane

Acknowledgments

The contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIFA. We also wish to thank Ms. Michele Mims, our lab manager, for all her help and guidance.

Additional information

Funding

This work was supported by funds fully provided by U.S. Department of Agriculture (USDA NIFA award: NC.X-314-5-18-130-1).