Biotechnologie, Agronomie, Société et Environnement (Jan 2015)
Co-compostage de boues de laiterie et de fumier de bovins à l'Ile de la Réunion : hygiénisation, pertes de nutriments et homogénéité du compost produit
Abstract
Co-composting of sludge and dairy cattle manure in Réunion (France): sanitization, nutriment losses and compost homogeneity. Description of the subject. Nutrient balance, windrow homogeneity and the sanitization of composts obtained from the co-composting of dairy sludge and cattle manure were investigated in Réunion at the request of the island's dairy industry, which wants both to develop the agronomic valorization of dairy sludge and to satisfy regulatory constraints on the island. Objectives. The aims of this experiment were to evaluate the feasibility of co-composting cattle manure with dairy sludge and to determine the quality of the compost produced. Method. Three heaps of manure with two doses of dairy sludge were established (on a mass basis): manure alone (T), manure ⅔ + sludge ⅓ (B1) and manure ½ + sludge ½ (B2), with a bulk density of 305, 566 and 630 kg·m-3 and a free air space of 72%, 48% and 42%, respectively. The heaps were turned after 21 days. Total composting time was 142 days. Results. During the experimentation, the temperature remained high and above 55°C for 40 days for the pure manure heap T, for 29 days for heap B1 and for 34 days for heap B2. During composting, heap T lost 69% of its wet mass and 64% of its initial volume, while heap B1 lost 71% and 44% and B2 lost 68% and 49%, respectively. Heap T lost 54% of its organic matter (OM) and 15% of its initial nitrogen (N); the respective levels of loss for B1 were 51% and 42% and for B2 56% and 50%. The heterogeneity of the dry matter (DM) and N content decreased during composting for heaps T and B1, whereas it increased for heap B2. Conclusions. The composts obtained were in accordance with the French standard NFU 44-51 (T) and the French standard NFU 44-95 (B1 and B2), except for the DM content criterion for B1 and B2. Relative to bovine manure compost, compost with the addition of sludge (⅓) was found to be enriched (on a fresh weight basis) in N (+ 15%), in P (+ 40%), whereas it was depleted in K (- 20%).
