| Composting is one element of waste management. It allows waste to be transformed into a valuable product. The processes involved and the final product, however, may vary in terms of quality, efficiency or security. Models have been established to represent some features of the composting process, but never all of them together. We hypothesized that all the key features from the literature could be gathered in one model. This model should be qualitatively faithful, reliable, and easily adapted to any situation. We used COMSOLTM, software that uses proven algorithms and the finite element method to solve partial differential equations in high spatial resolution in up to three dimensions. The behavior of this model was studied through parameter variations and sensitivity analysis. Patterns in temperature, biomass, substrate, oxygen and water concentration curves were consistent with the typical curves found in literature about composting. Initial water concentration and airflow were found to have an important impact on the composting process, while inlet air temperature did not. The resolution of the mathematical problem in a two-dimensional, longitudinal cross-section of the rectangular vessel allowed the observation of spatial patterns. This model can be used as a basis for further studies as new features are easy to implement. It can likewise be adapted to any apparatus, which makes it useful for comparative analysis. The suggested model, however, has yet to be validated against a physical system and this should be the next step. |
