Review of responses to a landfill modelling challenge

This paper reviews the responses from various international research groups to a challenge to model and predict the performance of a well-constrained laboratory experiment on the settlement and biodegradation of municipal solid waste (MSW). The paper outlines and compares the modelling approaches taken by the various groups and compares their predictions against actual long-term data from the experiment. The opportunity to compare models side-by-side against a common dataset has been extremely valuable in highlighting differences in approach, input parameters and identifying areas that need further investigation. One of the main differences identified related to hydrolysis, with three different algorithms used. Within the context of this modelling challenge it was not clear which was the appropriate formulation to use and thus the need for further work in this area was highlighted. This is also an example where the need to standardise on one pathway (or algorithm) could be investigated. There appears to be a clear imperative for settlement models to include a component for mechanical creep. An objective of the modelling challenge was to create a framework by which various models can be compared and act as a starting point for discussion and further collaboration in the future. This paper forms a starting point to this process.