Particle-scale modeling of oxygen uptake rate during pig manure-wheat straw composting: A new approach that considers surface convection

A new oxygen uptake rate (OUR) model that considers surface convection between composting materials and gas (Q(surf)) has been developed for the composting of pig manure and wheat straw. This was found to provide a more precise simulation of maximum OUR, which was especially true for the thermophilic phase due to a significant increase in the temperature difference between the composting materials and gas in the bottom part of reactor. Heat contribution analyses indicated that Q(surf) heat loss represents 8.86% of the total, implying that Q(surf) needs only be quantified for large-scale composting systems, and so can be omitted with systems in which there is a small exchange-surface of composting materials. Sensitivity analyses suggested that expanding the exchange-surface could protect microorganisms from overheating and be beneficial to degradation. These findings provide a theoretical basis for improving simulation precision, while also further elucidating the heat transfer mechanism during composting. (C) 2016 Elsevier Ltd. All rights reserved.