IWWG Task Group on
LANDFILL MODELLING
Chair: Dr. John McDougall
Background to the role of the IWWG Landfill Modelling Task Group ( LMTG)
The need to model a variety of landfill processes has assumed increased significance as requirements to actively manage landfills to minimise environmental emissions and maximise resource recovery (e.g. energy from landfill gas, and airspace) intensify. Modelling is now emerging as a powerful tool in the solution of landfill problems.
Recent developments and improvement of models describing complex processes within the landfill structure have led to an increasing recognition of their utility, demonstrating their suitability for use in solving future landfill problems. This aspect becomes even more relevant when applied to the construction of bioreactor landfills or to the monitoring and risk assessment of conventional landfills during the operating or aftercare stage.
With respect to the post-closure and aftercare period, little experimental or field data are available. This is the point at which appropriate models could improve the understanding of the ongoing processes and transfer model-based experience into technical solutions aimed at improving conditions for biodegradation, leachate transport, moisture distribution, etc.
Considering the multidisciplinary nature of landfill processes and the creation of powerful modelling tools, the formation of an IWWG Task Group on Landfill Modelling was proposed to unite international expertise and knowledge in relevant areas.
Role and activities of the Task Group
The Task Group (TG) formed with a range of activities in mind. These activities are summarised in the figure below.
The TG is firstly a contact point and virtual repository for expertise and information on landfill modelling. The contact point can provide access to expertise through the mailbase of members, through which the most up to date information on landfill models, their form and function, can be accessed. Many of the Task Group members are authors of internationally recognised landfill models or their co-workers and typically will be involved with current landfill modelling research. It is to be expected that such a group could join to stage a valuable and productive series of meetings and discussion. Indeed such activities have been taking place for a number of years; for example, the Hydro-Physico-Mechanics of Landfills workshop series (Grenoble, 2005; Southampton, 2007; Branschweig, 2009; Cantabria, 2011), the 2007 Southampton Landfill Modelling Challenge (Beaven, 2008) and a small workshop on moisture measurement in waste, which took place in Braunschweig in 2009.
However, formal establishment of the LMTG and its inaugural meeting did not take place until the Sardinia 2009 symposium. Professor Andreas Haarstrick of the Technical University of Braunschweig was elected as the group chair. A small (ash cloud eruptions!) business meeting took place at ADEME in Paris in April 2010.
The Paris meeting was timed to coincide with a meeting of another IWWG TG, the Sustainable Landfilling TG (SLTG). This confluence was important enabling the LMTG to formulate a list of priority issues or tasks facing landfill modellers. Issues such as boundary conditions, scale-dependent data and waste characterisation were identified. Whilst initial discussions were fruitful, there remains work to be to contextualise the priority tasks. In particular, it is important that the priority issues are defined in the context of the practical needs of waste management industry. Thus the LMTG is working to identify strategic priorities, e.g. the scope of a data bank by which models can be validated, the formulation of model developments that can contribute to the needs of landfill designers, operators and regulators. Strategic priorities are the outward face of LMTG serving to enhance the value of the work of the group members to the wider waste management community.
In addition, the TG is establishing technical priorities. These will constitute an active agenda by which group members can refine model development goals. Technical priorities will be a product of the technical insight of the TG members, i.e. the modellers, and the capability of their models. The technical context will reflect the practical context elucidated through contact and discussions with the waste management industry and SLTG. Indeed, as noted, a joint meeting of these two TGs has already taken place and informal link roles established. It will also seek to maximise the usefulness of new developments by harmonisation of modelling architectures, enabling ready incorporation into other models.
Recent developments and forthcoming events
Shortly after the recent business meeting, Prof Haarstrick announced his decision to stand down from the role of chair of LMTG. Nominations for his successor were invited by the group, after which Dr John McDougall was appointed to the role. Dr McDougall is a Reader in the School of Civil Engineering and the Built Environment at Edinburgh Napier University. He comes to landfill modelling from a geotechnical engineering background and has been working on landfill models for over 15 years.
It is necessary now to consider the management of LMTG and the progression of its activities, which will be one of the topics of discussion at the next business meeting.
John McDougall, chairman of the Landfill Modelling Task Group
The next LMTG business meeting will take place at the University of Cantabria, Santander on April 29, 2011. It is scheduled to coincide with HPM4, the next Hydro-Physico-Mechanics of Waste workshop.
The HPM4 workshop will be held in Santander, Spain, on 27-28 April 2011. Recent research on hydrological, physical/ mechanical and bio-chemical properties of waste will be addressed in the workshop, covering the following topics: waste characterization and landfill behaviour, landfill management and optimization, monitoring and data management, landfill modelling and the Second Landfill Modelling Challenge. Emphasis will be on the latest findings from the measurement and characterization of waste moisture content and waste mechanics. Further information about HPM4 can be obtained from Amaya Lobo (loboa@unican.es).
The second Landfill Modelling Challenge (www.lmc2.org) is currently open for entries, and contributors are invited to present their results at a specially convened session at HPM4. The modelling challenge is based around the operation and performance of a discrete landfill cell. Participants are invited to use their own (or others!) models to make predictions about how they believe the landfill cell behaved over a period of 3½ years, with regard to:
- Waste degradation and gas evolution;
- Waste composition changes over time;
- Leachate chemistry; and
- Settlement.
The geometry of the cell together with analyses of waste composition and amounts landfilled are provided. Details are also given of leachate and gas control infrastructure, together with volumes of infiltration, clean water added and volumes of leachate recirculated and removed. Limited leachate analyses have also been provided (see www.lmc2.org).
Contact person:
John McDougall
E-mail: j.mcdougall@napier.ac.uk
Next Task Group Meeting
Next LMTG Meeting will take place in the framework of Sardinia 2011 symposium.