One-dimensional spatial model for self-heating in compost piles: Investigating effects of moisture and air flow

Review on Self-Heating of Biomass Materials: Understanding and Description

“…The models are mostly based on energy and mass conservation to quantify the coupling between the reactions of heat generation and the transport of heat and mass in porous solid materials. The model equations in general forms ,, are the energy balance equation for heat transfer, and mass balance equation for transport of the species, for example, oxygen, where ρ, C p , λ, and ε are the bulk density (kg/m 3 ), specific heat capacity (J/(kg·K)), effective thermal conductivity (W/(m·K)), and porosity (unitless) of the bulk material, respectively, ρ g , C p g , and u are the density (kg/m 3 ), specific heat capacity (J/(kg·K)), and flow velocity (m/s) of the gases in the pores, respectively, T is the temperature (K), t the time (s), C j is the concentration (mol/m 3 ) of species j , D j is the effective diffusivity (m 2 /s) of species j inside the bulk material, q i is the heat source i accounting for the rate of heat generation (W/m 3 ) from the physical, biological, or chemical process, and R j is the mass source or sink, representing the rate of production or consumption of species j (mol/(m 3 ·s)). In eqs and , the left-hand side is the accumulation term of heat or mass, the first term on the right-hand side represents the thermal conduction or species diffusion, and the second term on the right-hand side denotes the convective heat or gas transport.…”

“…Both the biological activity of microorganisms and chemical oxidation of cellulosic materials were considered and the diffusion of oxygen in the pile was also coupled. The model was applied to predict self-heating in compost piles of sewage sludge and the critical conditions and pile temperature and configuration for spontaneous ignition. , The model was extended by Zambra et al to include the heat effect of water vaporization and consider the effects of moisture on both the biological activity and chemical oxidation and by Luangwilai and co-workers to incorporate the effects of convective heat and oxygen transport, , the effects of the moisture on the biological activity and chemical oxidation, and the water evaporation and condensation in the pile. , The developed model was recently applied to describe the self-heating process in stockpiles of wood bark and evaluate the impact of humidity change on self-heating and spontaneous ignition …”

Moisture-Induced Pattern of Gases and Physicochemical Indices in Corn Straw and Cow Manure Composting

“…Nonetheless, insufficient moisture content influences pile dehydration and slows down biological processes [16]. Labile and anoxic conditions established during composting also result from insufficient and excess moisture utilization [17,18]. Although these instances seemingly affect the composting process, a comprehensive mechanism surrounding the dynamics of moisture on the emission patterns of gases is less understood due to the diversified range of moisture regimes that have been reported from one study to another [19,20].…”

Application of Optimization and Modeling for the Composting Process Enhancement

“…The aforementioned mathematical model described the growth of microorganisms (Contois kinetic model), substrate consumption, oxygen and heat exchange in terms of partial differential equations. Alternatively, Luangwilai et al [108] proposed a one-dimensional model for the change in energy, oxygen, steam and liquid water during composting in the compost pile, while He et al [26] used a three-dimensional approach to describe the temporal and spatial variations in temperature and oxygen concentrations during aerobic composting. The importance of oxygen concentration variation during aerobic composting of organic waste was also modeled by Martalo et al [109].…”