This issue of Waste and Resource Management contains the second group of papers in response to the challenge issued to the landfill process modelling community described by Beaven et al.1 in the August 2008 issue. In summary, groups of landfill process modellers internationally were invited to predict the progress of a controlled waste degradation experiment on the basis of some limited initial data. Responses to the challenge by three groups of landfill process modellers in Spain, the UK and Germany were described in the August issue in the papers by Lobo et al.,2 Clewes et al.3 and Reichel and Haarstrick.4
In this issue, two further responses are given in the papers by White5 and McDougall,6 both of which use quite sophisticated models with some degree of hydro-bio-geomechanical coupling. The actual settlement behaviour of the waste due to both degradation and mechanical creep over the full 919 days of the experiment was described in the paper by Ivanova et al.7 The elemental and chemical changes (e.g. cellulose and hemi-cellulose) in the waste and leachate composition during the course of the study are described in the paper in this issue by Ivanova et al.8 A critical comparison between the overall observed behaviour and that predicted by the various models is given by Beaven,9 in a review which provides a valuable summary of the state of the art in landfill process modelling as well as identifying current uncertainties and research needs. The authors of the prediction papers are invited to respond to this paper and make further observations regarding the fit between their model and the experimental data, for publication in a future issue of Waste and Resource Management.
The final paper in this issue, by Ivanova et al.,8 describes the changes in the elemental and chemical content of the waste and relates them to gas generation, waste composition and ultimately the anaerobic degradation potential of municipal solid waste (MSW). This is an important consideration, especially in the context of assessing the effectiveness of waste treatments prior to landfilling for compliance with the EU Landfill Directive, the potential for biogas extraction, and the progress of historic landfills towards completion.
I would like to repeat the remarks made in the editorial in the August 2008 issue of the journal, and to emphasise that at the start of the challenge, the modellers were given only the information contained in the paper by Beaven et al.1 The behaviour they were trying to predict (reported by Ivanova et al.7) was not revealed to them until after their predictions had been submitted to the challenge organisers.
On behalf of the Institution of Civil Engineers and the journal's editorial panel, I would like to thank once again both the organisers of the challenge and the authors of the modelling papers for being brave enough to rise to it. Their efforts have provided us with
a definitive statement of the current state of the art in understanding and modelling landfill processes
an archival record of the progress that has been achieved in this area over the past six years or so
the starting point for the further developments needed if we are to meet the real challenge of returning residual wastes to the environment sustainably.
Waste and Resource Management is part of the Proceedings of the Institution of Civil Engineers. The journal aims to publish original contributions on research and practice relating to all civil engineering and construction aspects of the resource management cycle, from waste minimisation through the reuse and processing of waste materials to the management and disposal of residual wastes. Articles covering relevant legislation, standards, socio-economic and sustainability matters are welcomed.
The journal's website is currently averaging over 1000 visits per month (www.wasteandresourcemanagement.com). I hope the increasing impact of the journal will encourage readers to write in with a discussion point on one or more of the papers in this issue, and/or to contribute a paper, technical note, briefing or opinion of their own.
