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The University of Southampton
Engineering

Research project: Understanding landfill processes

Currently Active: 
Yes

Waste mechanics, settlement, degradation and landfill processes modelling

Background

Landfills can be thought of as active waste treatment plants, where biochemical processes act on and degrade landfilled solid waste causing settlement of the landform and creating landfill gases and leachate.

Electricity generation
Renewable energy from landfills

Landfill gas (LFG) is a powerful greenhouse gas, but proper control measures can prevent or at least minimise emissions to the atmosphere, and utilisation systems can convert LFG into electricity. Until 2006, LFG was the largest single contributor to renewable energy in the UK.

Our research has involved the investigation of fundamental landfill processes, through carefully controlled experiments on waste mechanics, degradation and settlement through to the development of coupled numerical models.

Waste Mechanics and settlement

The Landfill Directive requires that wastes are subjected to pre-treatment prior to landfilling, in part to reduce the biological content of household waste.  One form of treatment, known as mechanical-biological treatment or MBT, typically involves shredding or grinding of wastes prior to accelerated aerobic (often referred to as composting) or anaerobic degradation.  We have undertaken research into the mechanical properties of the residual wastes from these processes which may have very different properties to untreated wastes in terms of their mechanical behaviour (which impacts on the physical stability of landfills and hence their risk of landslides and pollution), the amount of gas and fluid which will be produced and the timescales over which gas and fluid production will occur.

The effect that MBT treatment  has on the mechanical strength of the residual waste stream was investigated at a fundamental level by investigating the effect that individual particles and shapes of particles has on waste mechanics.  Experiments into waste strength were undertaken using shear box apparatus, and purpose built anaerobic reactors where the waste was subject to a constantly applied load  were used to investigate waste settlement, degradation and gas generation.

LDAT

Coupled numerical models

We have developed a coupled numerical model LDAT to simulate landfill degradation, settlement and the formation and transport of liquid and gas.  The model is freely available for download at the LDAT project website.  A particle based numerical model, DEGAS, was also developed to investigate gas and liquid flow in wastes at the pore network level.

These models have contributed to the development of design tools for landfill remediation systems, with two specific remediation techniques (flushing and aeration) being targeted to provide a context for the work.

 

Related research groups

Infrastructure Group
Waste Management
causing surface water ponding and increased infiltration
Landfill settlement
to determine settlement, degradation and gas generation
Sealed testing of waste under load
Shear box for waste testing
..and the impact of crushing on fluid flow
Replicating waste particles

Related Staff Member

Related Staff Member

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