Heat partition during composting process of cattle manure

International audienceMost of the heat dissipation occurs when water evaporates. After heap turning, around one half of the heat production is stored in the heap until the maximum temperature is reached. Then, the sensible heat represents around another half of the heat production.Heat is produced during composting process by aerobic degradation of solid cattle manure. Our target was to quantify the kinetic of heat partition between the heap itself, and losses in the air as water vapour or sensible heat. One ton of cattle manure was disposed during six weeks in two small cells with controlled air temperature. One heap has been turned over twice and the other not. We measured the sensible heat, water vapour and carbon dioxide lost by each cell, and the temperature distribution in each heap. Most of the heat dissipation occurs when water evaporates. After heap turning, around one half of the heat production is stored in the heap until the maximum temperature is reached. Then, the sensible heat represents around another half of the heat production, and the heat storage becomes negligible. Our results suggest that extensive heat retrieval is possible on the farm with water pipes disposed near the top or the bottom of the heap. More intensive heat retrieval should include the condensation of the water vapour emitted. (Résumé d'auteur