Effect of temperature on methane production from field-scale anaerobic digesters treating dairy manure

Authors: ARIKAN, OSMAN - Istanbul Technical University; Mulbry, Walter; LANSING, STEPHANIE - University Of Maryland

Submitted to: Waste Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2015
Publication Date: 6/15/2015
Publication URL: http://handle.nal.usda.gov/10113/61547
Citation: Arikan, O., Mulbry III, W.W., Lansing, S. 2015. Effect of temperature on methane production from field-scale anaerobic digesters treating dairy manure. Waste Management. 43:108-113.

Interpretive Summary: Anaerobic digestion of dairy manure results in the production of biogas that can be used as a renewable source of electricity on-farm or sold to the distribution grid. Anaerobic digestion can also reduce greenhouse gas emissions and odors. Temperature is a critical parameter for anaerobic digestion since it influences both system heat requirements and biogas production. Although anaerobic digestion can take place under a range of temperatures, temperatures of 35 to 37 C (95 to 99 F) are typically recommended for biogas production from animal manure. However, digesters require a significant amount of heat energy to maintain temperatures at these levels. The objective of this study was to evaluate the effect of two relatively low digestion temperatures (22 and 28 C (72 and 82 F) on biogas production using replicate field-scale dairy manure digesters. Results showed that biogas production values of digesters operated at 22 and 28 C were about 70% and 87%, respectively, of the values from FS digesters operated at 35 C. The results suggest that anaerobic digesters treating dairy manure at 28 C were nearly as efficient as digesters operated at 35 C, with 70% of total methane achievable at 22 C. Small farm digester systems that may not have access to waste heat from electrical generation, could efficiently operate at these lower temperatures to produce methane and to reduce greenhouse gas emissions and odors. Farms with larger digester systems could also choose to operate at these lower temperatures if reducing digester heating would allow for more valuable uses of their heat energy such as drying solids or treating liquids to remove nutrients. These results will be of use to the dairy industry, extension agents, and government agencies working to lower the cost of anaerobic digesters for bioenergy production and greenhouse gas reduction.

Technical Abstract: Temperature is a critical factor affecting anaerobic digestion because it influences both system heating requirements and methane production. Temperatures of 35-37°C are typically suggested for manure digestion, yet in temperate climate digesters, require a considerable amount of additional heat energy to maintain these temperatures. In this study, the effects of lower digestion temperatures (22 and 28°C), on methane production from dairy digesters were evaluated and compared with 35°C using duplicate replicates of on-site field-scale (FS) digesters with a 17-day hydraulic retention time. After acclimation, the FS digesters were operated for 12 weeks using solids-separated manure at an organic loading rate (OLR) of 1.4 kg volatile solids (VS) per cubic meter-day, and then for 8 weeks using separated manure amended with manure solids at an OLR of 2.6 kg VS per cubic meter-day. Methane production values of the FS digesters at 22 and 28°C were about 70% and 87%, respectively, of the values from FS digesters at 35°C. The results suggest that anaerobic digesters treating dairy manure at 28°C were nearly as efficient as digesters operated at 35°C, with 70% of total methane achievable at 22°C. These results are relevant to small farms interested in anaerobic digestion for methane reduction without heat recovery from generators or for methane recovery from covered lagoon digesters.