Closure to "landfill settlement with decomposition and gas generation" by Ertan Durmusoglu, M. Yavuz Corapcioglu, and Kagan Tuncay

The authors appreciate and welcome the comments of Miller and Clesceri who have significantly contributed to the landfill research. In our paper, a one-dimensional numerical model for simulating landfill dynamics of solid, liquid and gas phases in landfills was presented. We made an attempt to incorporate several mechanisms that are potentially important in the physical chemistry of landfills. We believe that the assumption of deformable waste media is a strong step forward in simulating landfill dynamics. We have shown this advantage by comparing our results with those obtained under the assumption of nondeformable waste. We agree with the discussers that this subject has long been overlooked due to the complexity of the problem and the common practice of using empirical models. An improved understanding of the underlying mechanisms for landfill refuse consolidation/settlement is necessary to build more realistic, and accurate settlement models. The main objective of our paper was to develop a landfill settlement model. Gas generation is an important component of this model but not necessarily the critical one. Besides gas generation, the model incorporates several other mechanisms. We believe that incorporation of system stress balance in our model is another significant improvement. As indicated by the discussers, there are a number of simplifications in our model. Considering the wide applications in the literature and the complexity of our settlement model, we have considered relatively simple approaches suggested by Findikakis and Leckie (1979), Emcon Associates (1980), and Hossain et al. (2003). In our paper, we used a theoretical gas yield that serves as a maximum boundary for gas production which is based on the assumption that favorable environmental conditions exist for bacterial well-being. Miller and Clesceri (2003) developed a gas generation model which is a better representation of actual open environments. Their model allows anaerobic or aerobic decomposition of any local municipal soil waste (MSW) stream profile. On the other hand, given the heterogeneous nature of landfill material as a whole and the variation of biodegradable material within it, it is still doubtful if gas yields can be accurately estimated. Nevertheless, the inclusion of Miller and Clesceri’s gas generation model in the context of deformable landfills has the potential to be an important advance in landfill research