Thermo-Hygrometric Activation of Cold Mushroom Compost through Coupled Modeling of Heat, Moisture, Airflow and Biological Heat Generation

This study develops a coupled thermo-hygrometric model for the activation of cold mushroom compost initially at approximately 3 °C and warmed toward a target temperature of 23 °C. The formulation combines local thermal non-equilibrium heat transfer, forced airflow through a porous medium, water-vapor transport, liquid-water redistribution, evaporation and condensation, oxygen transport, and temperature-, moisture-, and oxygen-dependent biological heat generation. A one-dimensional finite-volume implementation was used to examine the principal cold-start mechanisms and the effects of inlet-air temperature, relative humidity, and airflow rate. For the reference parameterization, the predicted time required for 95% of the modeled compost domain to reach 23 °C was approximately 21.4 h. Phase change reduced the corresponding activation time from 32.7 to 28.9 h relative to sensible heating alone, whereas inclusion of biological heat generation further reduced it to 21.4 h. Airflow produced the strongest response among the investigated external variables, while increased humidity provided a smaller but systematic benefit through latent heat release. The results demonstrate a transition from externally dominated warming to biologically assisted heating and show that mean temperature alone is insufficient for defining process completion. The framework provides a physics-based basis for mechanistic analysis and subsequent development of improved cold mushroom-compost conditioning strategies.