Understanding the role of moisture in the self-heating process of compost piles

This paper considers the self-heating process which occurs in a compost pile using one-dimensional spatially-dependent models and incorporating terms that account for self-heating due to both biological and oxidation mechanisms. As the moisture content in a compost pile is a crucial factor in its degradation process, we utilise a model which incorporates four mass-balance equations, namely, energy, oxygen, vapour and liquid water concentrations, to investigate the behaviour of compost piles when moisture content is present. Analyses of different initial water contents within a compost pile, different ambient relative humidities and different amounts of water added to the pile by rainstorms are undertaken. We show that the effects of the ambient relative humidity are not significant but that a rainstorm either accelerates or decelerates a compost pile's self-heating process significantly depending on the initial moisture content of the compost materials and the amount of water that is added.