CERES :: Browsing by Author "Smith, Richard"

Browsing by Author "Smith, Richard"

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Open Access
Achieving equilibrium status and sustainable landfill - the holy grail?
(The Waste Conference Ltd, 2004-09) Hall, D. H.; Gronow, Jan R.; Smith, Richard; Blakey, N.
This paper presents the results of a research contract jointly funded by the Environment Agency and ESART examining the residues of likely post-Landfill Directive waste streams that will need to go to landfill and the time taken to achieve sufficient stabilisation such that management controls can be removed. The first part of the project has identified a number of processes that are likely to be adopted by the waste management industry in order to meet the biodegradable waste diversion targets. Both leachate quality and landfill gas generation data has been assessed for each residue stream. Forward modelling has been undertaken on these data using LandSim2.5 within GoldSim to assess the likely period of management needed in order to achieve equilibrium status.
Open Access
Air quality and worker health effects in materials recovery facilities (MRFs) in England and Wales.
(Eurowaste, 2003-10) Gladding, T.; Thorn, Jörgen; Smith, Richard
There are varying types of Materials Recycling Facilities (MRFs, also known as Materials Recovery Facilities, or Materials Recycling Factories) in operation in the UK and throughout Europe. A full outline of the various types of MRF operations is given by the Institute of Wastes Management (IWM 2000). This review concentrates on MRFs used to sort and process sourcesegregated household and commercial waste, the most common type. A MRF that deals with household and commercial waste is defined as a central operation where source-segregated, dry, recyclable materials are sorted, mechanically or manually, to market specifications for processing into secondary materials.
Open Access
Application of DR4 and BM100 Biodegradability tests to treated and untreated organic wastes
(2007-10) Godley, Andrew R.; Lewin, Kathy; Frederickson, Jim; Smith, Richard; Blakey, N.
The aerobic DR4 and anaerobic BM100 biodegradability tests are currently applied in England and Wales for monitoring the reduction in biological municipal waste (BMW) achieved by mechanical biological treatment (MBT) plants (Environment Agency 2005). The protocol is applied only when outputs are landfilled and is based on estimating the reduction in potential biogas production between the MBT input, municipal solid waste (MSW), and all of the landfilled outputs, using the BM100 test. As this is a long term 100 day test the more rapid 4 day DR4 test may also be applied as this has been shown to correlate with the BM100 test. We have now applied the DR4 and BM100 tests to 132 organic waste samples including untreated and treated BMW and specific organic wastes. The results indicate that the correlation between the DR4 and BM100 tests has proved valid for mixed MSW derived BMW wastes. However when both tests are applied to specific organic wastes such as turkey feathers, cardboard packaging waste and pizza food wastes the correlation between the tests is less strong. It is concluded that the use of the DR4 and BM100 test correlation is valid for its designed application (monitoring MBT processes treating MSW derived mixed BMW), but that caution should be exercised when applying both tests to specific single component organic wastes.
Open Access
Appraisal for options of solid recovered fuel (SRF) utilisation within the UK
(2006-11-29T00:00:00Z) Hill, D.; Garg, A.; Smith, Richard; Pollard, Simon J. T.; Longhurst, Philip J.
In view of the rising prices of non-renewable fossil fuels and regulatory obligations affecting waste management, interest is growing for the use of waste derived fuels in energy intensive facilities in Europe. However, major concerns with the use of such fuels include the quality of fuels, its source of generation, gaseous emissions and public acceptability. This paper presents the various production methods for solid recovered fuels (SRF) from municipal solid waste (MSW) and the potential options for its use in the UK. SRF can be produced by mechanical biological treatment (MBT) methods using bio-drying process or by extensive mechanical treatment. MBT involves a series of mechanical and biological steps, depending upon the input waste properties, aimed at producing an SRF. SRF compositions vary according to the application and can comprise of paper, plastic, wood, textile and organics. The European Technical Committee CEN/TC 343 “Solid Recovered Fuels” classifies SRF on the basis of net calorific value (NCV), chlorine content and mercury content. This classification system was prepared after extensive consultation with end-users. In the UK, the main potential outlets for MSW derived SRF include cement kilns, power plants, industrial boilers (such as pulp and paper mill), dedicated SRF incineration facilities and advanced thermal treatment plants (such as gasification and Venice 2006: Biomass and Waste to Energy Symposium. Cini Foundation, Venice, Italy. 29 November – 1 December 2006. pyrolysis). Cement kiln operators prefer high NCV fuel, however, in spite of its lower CV in comparison to other waste derived fuels (like liquid solvents, tyres and MBM), it remains attractive due to its biomass fraction and cheap availability. Power plants are much more concerned with the biomass fraction, as it may bring revenues for them in the form of Renewable Obligation Certificates (ROCs). Similarly, gasification and pyrolysis techniques are also eligible for ROCs, but these are still not fully proven in the UK. The use of SRF is also of interest because of its potential to reduce greenhouse gas emissions, as the biomass rich fraction is considered ‘carbon neutral’. Thus, this assists energy facilities to meet the EU Emissions Trading Scheme targets. However, the application of SRF is not straightforward as legislation exists at EU and National level, which users need to comply with. In addition, technical, environmental and economic issues need to be addressed. On the other hand if more SRF can be used then this will greatly help the UK meet its obligations under the Landfill Directive and the mitigation of greenhouse gases.
Open Access
Appropriateness of selecting different averaging times for modelling chronic and acute exposure to environmental odours
(2007-04-01T00:00:00Z) Drew, Gillian H.; Smith, Richard; Gerard, Valerie; Burge, C.; Lowe, M.; Kinnersley, R.; Sneath, R.; Longhurst, Philip J.
Odour emissions are episodic, characterised by periods of high emission rates, interspersed with periods of low emissions. It is frequently the short term, high concentration peaks that result in annoyance in the surrounding population. Dispersion modelling is accepted as a useful tool for odour impact assessment, and two approaches can be adopted. The first approach of modelling the hourly average concentration can underestimate total odour concentration peaks, resulting in annoyance and complaints. The second modelling approach involves the use of short averaging times. This study assesses the appropriateness of using different averaging times to model the dispersion of odour from a landfill site. We also examine perception of odour in the community in conjunction with the modelled odour dispersal, by using community monitors to record incidents of odour. The results show that with the shorter averaging times, the modelled pattern of dispersal reflects the pattern of observed odour incidents recorded in the community monitoring database, with the modelled odour dispersing further in a north easterly direction. Therefore, the current regulatory method of dispersion modelling, using hourly averaging times, is less successful at capturing peak concentrations, and does not capture the pattern of odour emission as indicated by the community monitoring database. The use of short averaging times is therefore of greater value in predicting the likely nuisance impact of an odour source and in framing appropriate regulatory controls.
Open Access
Assessing significant harm to terrestrial ecosystems from contaminated land.
(Blackwell Publishing Ltd., 2005-12-01T00:00:00Z) Smith, Richard; Pollard, Simon J. T.; Weeks, J. M.; Nathanail, C. Paul
Abstract. Terrestrial ecosystem risk assessment remains in its infancy by comparison with the aquatic discipline, yet it is advancing quickly in response to increasing concerns surrounding soil quality and the sustainable use of soil. Several international frameworks have been developed during the last decade to aid decision-makers as the need for scientifically derived tools for determining ecological risk from land contamination has been recognized. From the regulatory viewpoint, the priority is establishing what to protect in order to prevent ecological harm. This is a complex issue requiring clear objectives in a risk assessment context. The most important factor in assessing ecological harm is whether or not ecosystem function is altered as a result of land contamination and, if it is, judging the significance. A consensus is developing that ecological risk assessment should aim to protect populations rather than individuals. This paper critically reviews recent developments in risk assessment for terrestrial ecosystems and land contamination in the UK, with emphasis on deriving a measure of ecological harm to assess ecosystem function. We seek to further justify the use of earthworms as a favoured indicator species for protecting ecological function. Guidance on how to measure harm in relation to ecological function is, however, still lacking.
Open Access
Assessment of municipal waste compost as a daily cover material for odour control at landfill sites.
(Elsevier Science B.V., Amsterdam., 2005-01-01T00:00:00Z) Hurst, C.; Longhurst, Philip J.; Pollard, Simon J. T.; Smith, Richard; Jefferson, Bruce; Gronow, Jan R.
The ability of municipal waste compost as a daily cover material to reduce the odorous emissions associated with landfill surfaces was investigated. Trials were carried out using landfill gas, a certified sulphurous gas mix and ambient air as a control. Odorous gas was passed through portable test column filled with compost at different densities (590 kg/m3 and 740 kg/m3). Gas samples were taken from the inlet, outlet and at varying column depths and examined using a combination of sensory analysis (olfactometry) and a novel analytical method (Transportable Selected Ion Flow Tube – TSIFT). Results for the trials using landfill gas showed a 69% odour reduction (OU/m3) through the column for compost with a bulk density of 590 kg/m3, and a reduction of 97% using compost with a bulk density of 740 kg/m3. TSIFT analysis showed an overall decrease in the concentration of terpenes, and sulphurous compounds in the outlet gas from the column for both bulk densities. No significant trend could be identified for the concentrations at different depths within the column. Results show the ability of compost to reduce landfill odours under differing conditions. The inconclusive data provided by TSIFT analysis may be due to the analysis of compounds that are not contributing to odour, and thus highlights the potential for synergetic effects and the importance of sensory measurement when examining odorous emission
Open Access
Biodegradability determination of municipal waste: an evaluation of methods
(The Waste Conference Limited, 2004-09) Godley, Andrew R.; Lewin, Kathy; Graham, Adele; Barker, H.; Smith, Richard
The Environment Agency is required to monitor the diversion of biodegradable municipal waste (BMW) from landfill. Reliable methods are needed to measure the biodegradability of municipal waste, both as mixed municipal waste and as individually separated fractions. An evaluation of several methods was carried out using a variety of organic materials typically found in municipal solid waste. The assessment considered biological and non-biological methods to determine which provides the bestfit surrogate measurement for relative waste biodegradability. The biological methods tested were: the aerobic specific oxygen uptake rate, dynamic respiration index tests, and the anaerobic biochemical methane potential test. The non-biological methods evaluated were: dry matter, loss on ignition, total organic carbon, total nitrogen, water extractable dissolved organic carbon, biological oxygen demand, chemical oxygen demand, lignin and cellulose content and cellulase hydrolysis. This paper also reviews how such tests can be used to measure the relative biodegradation of municipal waste and benchmark the relative diversion from landfill achieved by the pre-treatment of municipal waste in a mechanical biological treatment (MBT) process.
Open Access
Biodrying for mechanical-biological treatment of wastes: A review of process science and engineering
(Elsevier Science B.V., Amsterdam., 2009-06-01T00:00:00Z) Velis, C. A.; Longhurst, Philip J.; Drew, Gillian H.; Smith, Richard; Pollard, Simon J. T.
Biodrying is a variation of aerobic decomposition, used within mechanical–biological treatment (MBT) plants to dry and partially stabilise residual municipal waste. Biodrying MBT plants can produce a high quality solid recovered fuel (SRF), high in biomass content. Here, process objectives, operating principles, reactor designs, parameters for process monitoring and control, and their effect on biodried output quality are critically examined. Within the biodrying reactors, waste is dried by air convection, the necessary heat provided by exothermic decomposition of the readily decomposable waste fraction. Biodrying is distinct from composting in attempting to dry and preserve most of biomass content of the waste matrix, rather than fully stabilise it. Commercial process cycles are completed within 7–15 days, with mostly H2O(g) and CO2 loses of ca. 25–30% w/w, leading to moisture contents of <20% w/w. High airflow rate and dehumidifying of re-circulated process air provides for effective drying. We anticipate this review will be of value to MBT process operators, regulators and end-users o
Open Access
Characterisation of untreated and treated biodegradable wastes
(2007-10) Godley, Andrew R.; Frederickson, Jim; Lewin, Kathy; Smith, Richard; Blakey, N.
As part of a Defra sponsored project (WRT220), approximately 40 biodegradable wastes were characterised according to biodegradability (DR4 and BM100), total PTE content, C:N ratio and biochemical composition. Two leaching tests were employed; upflow percolation test and a one step LS10 test; eluates were analysed for TOC, pH, electrical conductivity, PTEs and a range of cations and anions. This paper contains a limited set of data for a selection of untreated and treated waste types representing four waste treatment processes (composting, MBT, MHT, anaerobic digestion). The DR4 and BM100 tests were found to be appropriate for a wide range of waste types but where possible they should be used in conjunction with other related tests. Longer-term MBT composting processes appeared to produce compost material with reduced ammonium concentrations and extractability of some PTEs. Carbon content (carbon analyzer - LECO) could be estimated as C = LOI/1.9 which is a routine operation. N LECO values were approximately 12% greater than the equivalent N Kjeldahl values.
Open Access
Charaterisation of treated wastes to support an evidence base for sustainable waste management.
(The Waste Conference Limited, 2006-09) Lewin, Kathy; Godley, Andrew R.; Turrell, J.; Smith, Richard; Frederickson, Jim; Graham, Adele; Gronow, Jan R.; Blakey, N.
Defra must consider policies and strategies to manage environmental challenges such as climate change and sustainability. At a basic level the strategies need good quality data on waste characteristics. The dataset for UK wastes, in particular the new generation of treated wastes, is not fit for this purpose. This paper outlines the gaps in knowledge needed to underpin policy development and initial findings from a new project funded under Defra’s Waste and Resource Management Research Programme. The project team from WRc, Open University and Cranfield University aims to improve understanding of the characteristics of treated organic and inorganic wastes, methods of testing and knowledge of treatment process performance. Potential opportunities from the research are also described. New data will be collated into the presentation.
Open Access
Comparative evaluation of SRF and RDF co-combustion with coal in a fluidised bed combustor
(2007-10-01T00:00:00Z) Garg, A.; Smith, Richard; Longhurst, Philip J.; Pollard, Simon J. T.; Simms, Nigel J.; Hill, D.
The experimental study reported here was carried out to assess the feasibility of municipal solid waste (MSW) derived solid recovered fuel (SRF) in energy recovery applications. SRF was prepared by grinding and blending the major MSW constituents such as paper, plastics, wood and textile. The percentage of various constituents was the same as from the Ecodeco process employing bio- drying followed by mechanical treatment. The heating value of synthetic SRF was ca. 21 MJ/kg (as received basis). The metal emission results from the SRF co- combustion with coal were compared with that obtained from coal mono-combustion and refuse derived fuel (RDF) co-combustion with coal. RDF was also derived from MSW and was obtained from a local mechanical treatment waste facility. Use of SRF as co-fuel does not increase the emissions of metals to the environment in the flue gas stream when compared to coal mono-combustion. In addition, use of MSW derived fuel reduces the arsenic release to the atmosphere. The results showed that most of the metals are retained in the ash components (except mercury). The mobility of metals depends on the volatility and type of feedstock.
Open Access
Comparison of a novel enzymatic biodegradability test method with microbial degradation methods
(2008-01-01T00:00:00Z) Wagland, Stuart Thomas; Godley, Andrew R.; Frederickson, Jim; Tyrrel, Sean F.; Smith, Richard
A novel enzymatic hydrolysis test (EHT) has been evaluated as a surrogate for conventional microbial biodegradability methods, using 37 assorted organic waste samples collected from diverse sources. The results of the EHT method are compared with those obtained from two conventional tests; the 4 day aerobic DR4 and 100 day anaerobic BM100 test methods currently applied in England and Wales. The EHT is based on the enzymatic hydrolysis of cellulosic materials and can be completed in less than 24 hours. Linear regression for 37 samples against the BM100 data showed the DR4 provided a correlation coefficient of r = 0.58; the EHT method gave a correlation of r = 0.62 for the total DOC release; and r = 0.77 for the DOC released from enzymatic hydrolysis. The correlations suggest that the EHT method may be better suited to a wider range of waste types when correlating with anaerobic BM100 test results since it more closely mimics the full extent of decomposition rather than that from the readily biodegradable fraction.
Open Access
Comparison of coal/solid recovered fuel (SRF) with coal/refuse derived fuel (RDF) in a fluidised bed reactor.
(Elsevier Science B.V., Amsterdam., 2011-06-01T00:00:00Z) Wagland, Stuart Thomas; Kilgallon, P.; Coveney, R.; Garg, A.; Smith, Richard; Longhurst, Philip J.; Pollard, Simon J. T.; Simms, Nigel J.
An experimental study was undertaken to compare the differences between municipal solid waste (MSW) derived solid recovered fuel (SRF) (complying with CEN standards) and refuse derived fuel (RDF). Both fuels were co-combusted with coal in a 50kW fluidised bed combustor and the metal emissions were compared. Synthetic SRF was prepared in the laboratory by grinding major constituents of MSW such as paper, plastic, textile and wood. RDF was obtained from a local mechanical treatment plant. Heavy metal emissions in flue gas and ash samples from the (coal+10% SRF) fuel mixture were found to be within the acceptable range and were generally lower than that obtained for coal+10% RDF fuel mixture. The relative distribution of heavy metals in ash components and the flue gas stream shows the presence of a large fraction (up to 98%) of most of the metals in the ash (except Hg and As). Thermo-gravimetric (TG) analysis of SRF constituents was performed to understand the behaviour of fuel mixtures in the absence and presence of air. The results obtained from the experimental study will enhance the confidence of fuel users towards using MSW-derived SRF as an alternative fuel.
Open Access
Development and application of an Enzymatic Hydrolysis test to assess the biodegradability of organic waste material
(2007-10-01T00:00:00Z) Wagland, Stuart Thomas; Smith, Richard; Godley, Andrew R.; Tyrrel, Sean F.; Blakey, N.
A novel and rapid biodegradability test method has been developed based on the enzymatic hydrolysis of cellulose. The test method consists of three phases, in which the first two phases consist of the pH buffer addition, and then autoclaving of the mixture and the final phase is the addition of the enzyme mixture and incubation. An initial investigation was carried out to determine the optimum conditions for the enzymes using standard commercial cellulose as the substrate. The optimised test was then applied to a wide range of organic waste samples including untreated and treated MSW derived mixed BMW, and specific wastes such as waste wood, packaging waste (cardboard), turkey feathers and green waste. The DOC released by enzymatic hydrolysis indicates that this could give an indication of the sample biodegradability. However the DOC released in phases 1 and 2 may also contain some biodegradable components (depending on the extent of biological treatment applied to the waste sample) and these would need to be differentiated from the non-biodegradable DOC and used together with the DOC from phase 3 to give the best possible biodegradability indication.
Open Access
Dispersion of bioaerosols from composting facilities.
(2006-09-01T00:00:00Z) Drew, Gillian H.; Tamer Vestlund, Asli; Taha, M. P. M.; Smith, Richard; Longhurst, Philip J.; Kinnersley, R.; Pollard, Simon J. T.
The promotion of composting as an option for sustainable waste management has raised concerns regarding public health impacts of exposures to potentially hazardous bioaerosols. Recent source term experiments show that bioaerosol emissions are episodic and that peak emissions are related to compost agitation. The Environment Agency requires risk assessments for facilities that have sensitive receptors within 250m of their boundary. In order to improve current risk assessment methodologies, improved predictions of bioaerosol dispersal are required. Dispersion modelling has been successfully used to determine dispersion of odours from waste management. In this paper, bioaerosol concentration data measured at a composting facility is analysed in an ongoing series of model experiments, using the ADMS air dispersion model. Initial modelling results reveal that the concentrations of bioaerosols decrease rapidly with distance from the site, although under certain circumstances, it is possible that higher concentrations may still be present at 200m from the site boundary. However, dispersion models are not yet able to take into account all the properties of bioaerosols, in particular, their viability and their ability to aggregate and form clumps, which will affect the rate of dispersal. A series of experiments were designed to examine how the options within dispersion model affect the dispersion of bioaerosols and under which circumstances high concentrations may disperse to sensitive receptors. The results will be compared with bioaerosol measurements taken downwind of a composting facility, to determine the accuracy of the model predictions. This is the first stage in an attempt to design a best practice method for modelling bioaerosols.
Open Access
Environment Agency review of methods for determining organic waste biodegradability and municipal waste diversion.
(Aqua Enviro Technology Transfer, 2003-11) Godley, Andrew R.; Lewin, Kathy; Graham, Adele; Smith, Richard
The Environment Agency is required to regulate the landfilling of biodegradable organic wastes and their diversion from landfilling. Simple, cost effective, reliable and widely applicable methods for the measurement of organic waste and its biodegradability are needed for this activity. A review of such methods was carried out in order to select promising methods for an experimental screening exercise. The review considered both biological and non-biological methods including simple methods that may provide a surrogate measurement of waste biodegradability instead of the time-consuming biological methods. The biological methods selected for further evaluation were the aerobic specific oxygen uptake rate (SOUR) and dynamic respiration index (DRI) tests, and the anaerobic biochemical methane potential (BMP) test. The non-biological methods selected for further evaluation were dry matter (DM), loss on ignition (LOI), total organic carbon (TOC), total nitrogen (TN), water extractable dissolved organic carbon (DOC), BOD and COD, the lignin and cellulose content and the cellulase hydrolysis method. These tests are being evaluated on a wide variety of typical organic materials that might be found in municipal solid waste (MSW) such as newspaper corrugated paper, compost, kitchen waste (vegetable and animal), garden wastes (grass and twigs), nappies, cotton and wool textiles.
Open Access
Estimating Pollutant Removal Requirements for Landfills in the UK: I. Benchmark Study and Characteristics of Waste Treatment Technologies
(Taylor & Francis, 2006-12-01T00:00:00Z) Hall, D. H.; Drury, D.; Gronow, Jan R.; Rosevear, Alan; Pollard, Simon J. T.; Smith, Richard
Introduction of the EU Landfill Directive is having a significant impact on waste management in the UK and in other member states that have relied on landfilling. This paper considers the length of the aftercare period required by the municipal solid waste streams that the UK will most probably generate following implementation of the Landfill Directive. Data were derived from literature to identify properties of residues from the most likely treatment processes and the probable management times these residues will require within the landfill environment were then modelled. Results suggest that for chloride the relevant water quality standard (250 mg l−1) will be achieved with a management period of 40 years and for lead (0.1 mg l−1), 240 years. This has considerable implications for the sustainability of landfill and suggests that current timescales for aftercare of landfills may be inadequ
Open Access
Estimating Pollutant Removal Requirements for Landfills in the UK: II. Model Development
(Taylor & Francis, 2006-12-01T00:00:00Z) Hall, D. H.; Drury, D.; Gronow, Jan R.; Rosevear, Alan; Pollard, Simon J. T.; Smith, Richard
A modelling methodology using a leachate source term has been produced for estimating the timescales for achieving environmental equilibrium status for landfilled waste. Results are reported as the period of active management required for modelled scenarios of non-flushed and flushed sites for a range of pre-filling treatments. The base scenario against which results were evaluated was raw municipal solid waste (MSW) for which only cadmium failed to reach equilibrium. Flushed raw MSW met our criteria for stabilisation with active leachate management for 40 years, subject to each of the leachate species being present at or below their average UK concentrations. Stable non-reactive wastes, meeting EU waste acceptance criteria, fared badly in the non-flushed scenario, with only two species stabilising after a management period within 1000 years and the majority requiring >2000 years of active leachate management. The flushing scenarios showed only a marginal improvement, with arsenic still persisting beyond 2000 years management even with an additional 500 mm y−1 of infiltration. The stabilisation time for mechanically sorted organic residues (without flushing) was high, and even with flushing, arsenic and chromium appeared to remain a problem. Two mechanical biological treatment (MBT) scenarios were examined, with medium and high intensity composting. Both were subjected to the non-flushing and flushing scenarios. The non-flushing case of both options fell short of the basic requirements of achieving equilibrium within decades. The intense composting option with minimal flushing appeared to create a scenario where equilibrium could be achieved. For incinerator bottom ash (raw and subjected to various treatments), antimony, copper, chloride and sulphate were the main controls on achieving equilibrium, irrespective of treatment type. Flushing at higher flushing rates (500 mm y−1) failed to demonstrate a significant reduction in the management period requi
Open Access
Estimating Pollutant Removal Requirements for Landfills in the UK: III. Policy Analysis and Operational Implications.
(Taylor & Francis, 2007-01-01T00:00:00Z) Hall, D. H.; Drury, D.; Gronow, Jan R.; Pollard, Simon J. T.; Smith, Richard
The policy analysis and management implications for achieving landfill equilibrium status within a sustainable timescale (decades rather than centuries) are presented based on modelled results reported previously. Until relatively recently, timescale estimates suggested that equilibrium or landfill completion could be achieved within 40-60 years i.e. the same order of magnitude as financial provision for aftercare. However results of modelling in this study (reported in previous paper) suggest that timescales may be considerably longer (many centuries in some instances) suggesting that financial provision may be inadequate. The role of the most promising and available waste treatment technologies and strategic waste management options in contributing towards achieving equilibrium status are discussed. Results suggest that a re- examination of techniques for accelerating landfill stabilisation, including aerobic and bioreactor landfill, is warranted.