Nitrogen Availability from Swine Manure Following Anaerobic Treatment and Storage

Abstract

The purpose of this research was to determine the percentage of nitrogen excreted that needs to be land applied and the effects of three factors, facility type, geographic location and lagoon loading concentrations, on the quantity of nitrogen available for land application following anaerobic treatment and storage. This quantitative research was conducted on data collected from 1995 - 1997 to determine if a correlation exists between the lagoon inflow nitrogen concentration and the percentage of nitrogen removed from a lagoon for land application purposes and the causal-comparativeness of geographic location and facility type on the percentage of nitrogen removed for land application purposes. Because this thesis was developed as quantitative research, rather than experimental research, that is, the independent variables were not manipulated, there does exist a need to be cautious or tenuous in the conclusions achieved from this study.

The study consisted of 122 facilities in Missouri (107) and Oklahoma (15). The facility breakdown was 46 Breeding/Gestation/Farrowing and Nursery (B/G/F/N) units, 6 Breeding/Gestation and Farrowing (B/G/F) units, 6 Nursery, 62 Grower/Finisher (G/F) units and 1 each genetic multiplier and Artificial Insemination (AI). Each facility was evaluated for one to three years depending on the maturity of the lagoon system. Lagoon maturity was defined as being in operation for a minimum of two (2) years. Information pertaining to the nitrogen excretion, water use rates, lagoon concentrations and effluent removal rates were determined for each facility. Following three years of data collection, it was found that the average nitrogen availability (excluding application losses) of the facilities in this study was between 23% and 52% versus the MWPS-18 value of 15% - 30% and the AWMFH estimated nitrogen availability of 20% - 30%. The nitrogen availability is defined as the estimated nitrogen available for irrigation as a percentage of estimated nitrogen excreted.

The results of this study indicate that although statistically significant, there is not a strong correlation (r = -0.21) between nitrogen availability for land application and the concentration of nitrogen entering the lagoon without the effects of net rainfall. When the effects of net rainfall are included in the inflow nitrogen concentrations, the correlation is nearly identical with r = -0.22.

Using the t-test, geographic location was shown to not have a significant effect on the nitrogen availability for land application. An analysis of variance and Scheffe test was performed to determine if nitrogen availability differed significantly between facility types. The results show that facility type does affect the percent of nitrogen available with the B/G/F/N and Nursery, Nursery and GM and GM and G/F being the only facility combinations that do not significantly differ.