The effect of moisture content on solid-state anaerobic digestion of dairy manure from a sawdust-bedded pack barn

Authors: KIM, E - Chungnam National University; LEE, S - Chungnam National University; JO, H - Chungnam National University; JEONG, J - Chungnam National University; Mulbry, Walter; RHAMAN, S - North Dakota State University; AHN, H - Chungnam National University

Submitted to: Energies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2018
Publication Date: 2/25/2018
Publication URL: https://handle.nal.usda.gov/10113/5931565
Citation: Kim, E.J., Lee, S.H., Jo, H.S., Jeong, J.H., Mulbry III, W.W., Rhaman, S., Ahn, H.K. 2018. The effect of moisture content on solid-state anaerobic digestion of dairy manure from a sawdust-bedded pack barn. Energies. 11(3):484.

Interpretive Summary: The focus of this research is to improve technologies for manure treatment on dairy farms. Anaerobic digestion has emerged as an alternative technology to composting processes for treating high solids wastes such as manure/bedding mixtures. In addition to stabilizing manure and reducing its odor, digestion systems can be used to generate renewable electricity and to reduce emissions of the greenhouse gas methane. However, factors affecting high solids digestion processes are not well characterized. The objective of this research was to determine the influence of manure moisture content on the digestion of a high solids mixture of dairy manure and bedding from a sawdust-bedded pack barn. Results showed that digester performance (as measured by biogas production and solids removal) improved as the moisture content of manure/bedding mixtures was increased to saturated levels. Biogas production values from digesters containing a water saturated manure/bedding mixture (83% moisture content) were approximately 40% higher than values from digesters containing the manure/bedding mixture as it was collected from a sawdust-bedded pack barn (70% moisture content). Results also showed that solids removal values similarly improved (up to 36%) with increased moisture content. These results could be useful for those interested in new technologies for treating high solids agricultural wastes and to dairy farmers interested in improving on-farm biogas production.

Technical Abstract: The effect of moisture content on solid-state anaerobic digestion of dairy manure from a Korean sawdust-bedded pack barn was determined using laboratory-scale digesters operated at three moisture levels (70, 76, and 83% on a wet basis) at 37 C for 85 days. Results showed that digesters containing manure at 83% moisture content (equivalent to the water holding capacity of the manure) outperformed digesters containing 70 and 76% moisture content manure in terms of volatile solids (VS) reduction and biogas production. Biodegradable volatile solids (BVS) reduction in digesters operating at 83% moisture content was 75%. In comparison, digesters operating at 70 and 76% moisture content achieved lower levels of BVS reduction (55% and 67%, respectively). The cumulative methane yield from units operated at 83% moisture content was 0.09 Nm3/kg-VS. This value was approximately 40% and 20% higher than values from units operated at 70 and 76% moisture content, respectively. These results suggest that moisture levels near saturation are more favorable than lower levels for solid-state anaerobic digestion of dairy manure.