Anaerobic Storage of Commercial Pig Manures to Dissolve Phosphorus for Struvite Precipitation
Bibliographic record
Abstract
Removal of excess P from pig manure can be accomplished by the precipitation reaction to form struvite (MgNH4PO4 ?6 H2O). However, recovery is limited by the concentration of dissolved phosphorus, in form PO4-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 PO4-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 PO4-P responses, varying from almost no response to a significant drop in pH with corresponding increase in dissolved PO4-P and Mg. Manure pH and PO4-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 PO4-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 PO4-P during anaerobic storage, which increases the total recoverable P by struvite precipitation.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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) | 0.001 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".