Sustainable manure management via anaerobic digestion integrated with struvite precipitation
Notice bibliographique
Résumé
The amount of livestock waste produced is monumental due to the increase in intensive agriculture. The manure management stage is one of the largest contributors to the carbon footprint of the Canadian livestock sector. To mitigate these harmful effects, various manure management strategies have been undertaken. Anaerobic digestion (AD) is one of the methods used to treat manure sustainably, producing biogas (which has multiple applications) and digestate, a valuable by-product. Historically, digestate was applied to farmlands as a source of fertilizer. However, excessive application of digestates on agricultural lands leads to environmental problems: eutrophication, greenhouse gas (GHG) emissions, heavy metal, and pathogen contamination. To diminish the mentioned problems, the focus has shifted to finding alternate methods to treat these digestates that can reduce their impact but also give value-added products. Struvite precipitation is one such method wherein the produced crystals can be applied as a fertilizer. The struvite crystals contain good levels of magnesium, nitrogen, and phosphorus (elements crucial for a crop’s growth), with other benefits such as relatively low solubility, compact storage, easy transportation, lower GHG emissions, lower soil and water contamination due to reduced leaching while giving the same effect as conventional fertilizers in crop yield. Furthermore, struvite crystal production has been underutilized using agricultural waste streams which contain a considerable amount of nutrients that can be recovered and recycled, especially anaerobic digestates of nitrogen-rich livestock waste streams. This thesis aims to ascertain struvite production in an agricultural scenario from anaerobic digestates of varying compositions to encourage valorizing wastes for the recovery of nutrients and to implement sustainable circular economic principles. This is done by first devising a protocol to validate the conditions: pH 9, 1.5 Mg/P, and 240 rpm. Digestates obtained from the co-digestion of different wastes and mono-digestion of poultry manure were initially tested, where 3 sets of trials were done to see the efficacy of different phosphorus salts on nitrogen recovery and mass production. Nitrogen (N) recovery of ≥95% was achieved for all the digestates, also causing a substantial volatile fatty acids reduction. While the recovery was on par, the mass of crystals produced varied with the digestates, with a range of 0.33g/10 ml to 1g/10 ml being produced. To advance the idea of bio-economic sustainability, integration of AD with struvite precipitation is proposed. To determine its feasibility, the efficiency of high solids anaerobic digester using co-digested wastes was assessed for one representative cycle of operation of 77 days with more emphasis on the struvite precipitation, which was conducted at the end of the cycle to maximize recovery of nutrients and energy. The AD presented good results, with a maximum specific methane yield of 1.26 L CH4/g CODs fed for D1 (poultry and dairy manures and corn silage) and 1.49 L CH4/ CODs fed for D2 (poultry, dairy, swine manures and corn silage), which was achieved at the end of the respective operation cycle. The N recovery was very high (around 98-99%), producing 0.67 g/10 ml for all the phosphorus salts. The overall results of this study show that high N recovery is possible in co-digested wastes when struvite precipitation is used, with further opportunities to scale up and integrate this with AD to create a closed nutrient loop cycle. The goal is to show that struvite has immense potential in the agricultural sector, promoting a circular economy as it maximizes energy and nutrient production. The advantage of the struvite compound outweighs the direct usage of digestate as a fertilizer. Detailed research can be pursued to scale up the integration process and assess its capabilities as a fertilizer
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,001 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; les deux têtes enseignantes s’accordent sur ce qui est montré ici.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».