Anaerobic Storage of Commercial Pig Manures to Dissolve Phosphorus for Struvite Precipitation
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Bibliographic record
Abstract
<abstract> Removal of excess P from pig manure can be accomplished by the precipitation reaction to form struvite (MgNH<sub>4</sub>PO<sub>4</sub> <monospace>?</monospace>6 H<sub>2</sub>O). However, recovery is limited by the concentration of dissolved phosphorus, in form PO<sub>4</sub>-P, as it is typically only about 10% of total phosphate in liquid pig manure. To increase P recovery, manure can be stored anaerobically to increase acidity, which has been to shown to produce higher concentrations of PO<sub>4</sub>-P.. However, manures from different farms can vary markedly in chemical properties and this technique may not be effective in all cases. This experiment investigated chemical changes from anaerobic fermentation of manures collected from several commercial pig operations in Manitoba. Fresh manures were placed in triplicate stirred anaerobic digesters and monitored daily for pH and analyzed for total solids, volatile solids (VS), alkalinity, volatile fatty acids (VFA), dissolved and total nutrients (P, Mg, and Ca) on days 0, 4, 8, and 12. Under identical storage conditions, manures displayed different pH and PO<sub>4</sub>-P responses, varying from almost no response to a significant drop in pH with corresponding increase in dissolved PO<sub>4</sub>-P and Mg. Manure pH and PO<sub>4</sub>-P concentration were negatively correlated in all manures (-0.63 to -0.98). Through comparison with these and other manures, a relationship was found between manure alkalinity buffering and the acid forming effects of VS, expressed as mg/L of total alkalinity to g/L VS. Manures with low alkalinity/VS ratios became acidic during anaerobic fermentation and consequently increased in PO<sub>4</sub>-P concentration. Both VS and alkalinity are easily performed analyses and the ratio could be used to predict the suitability of a manure to release PO<sub>4</sub>-P during anaerobic storage, which increases the total recoverable P by struvite precipitation.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it