2002 Annual Report
Research
Effect of Solids Content in Swine Manure on Aeration Efficiency
Jun Zhu, Assistant Professor, Southern
Research and Outreach Center, Waseca, MN
Zhijian Zhang, Post-Doctoral Associate, Southern Research and Outreach
Center, Waseca, MN
Curtis Miller, Assistant Scientist, Southern Research and Outreach Center,
Waseca, MN
Funding Source
Minnesota Legislature Rapid Agricultural Response Fund
Objective
The objective of the project is to investigate the effect of solids content
in liquid swine manure on aeration efficiency, thus determining if solid-liquid
separation is needed as pretreatment prior to aeration to save energy.
Project Description
The aeration system in this study was composed of a 50-gallon container
equipped with a venturi air injector. Fresh swine manure at four solids
levels, i.e., 0.5%, 1.0%, 2.0%, and 4.0%, was tested. The aeration efficiency
corresponding to each solids content was determined by the oxygen transfer
coefficient (OTC), which was used as the criterion to differentiate the
influence of different manure solids content on aeration treatment.
Results
Data from this project indicate that using a solids-liquid manure separator will vastly improve the efficiency of aeration treatment of swine manure. That conclusion was based on the assessment of one parameter of the aeration process: oxygen transfer coefficient (OTC). When the amount of manure solids tested increased from 0.5% to 4%, it led to a reduction in OTC from 0.59/minute to 0.15/minute. This means that OTC in manure at 4% solids is reduced to about 1/4 the level of efficiency of what it would be in manure at 0.5% total solids level (0.59/minute divided by 0.15/minute). Put another way, the energy consumption for manure with 4% total solids is about four times that for manure with 0.5% solids content, in order to achieve the same aeration level. Therefore, the level of manure solids had a profound effect on the OTC in manure by aeration. Increasing the concentration of manure solids had a direct, negative correlation on the efficiency of the aerator.