Estimating the post-closure management time for landfills containing treated MSW residues.

The Landfill Directive will require the pre-treatment of MSW prior to landfilling. The removal of progressively increasing proportions of the biodegradable fractions from landfilled waste, and the UK Government’s commitment to increase recycling of key waste fractions, will lead to an inevitable change, from the disposal of raw MSW, to the disposal of MSW treatment residues, to landfill. This will undoubtedly change the type and rate of emissions from landfills. The question that this research project has sought to answer is “how long will active management be required for different MSW treatment residues?” The term equilibrium status has been used to define the end point beyond which management of wastes is no longer necessary. Calculating the equilibrium status of waste involves an assessment of the landfill gas emissions, leachate quality and hydraulic status of the landfill. These key parameters change with time as the landfill evolves. Equally, the engineering performance of a site is also changing with the gradual degradation of the liner and capping systems. The question posed above is therefore not easily answered

A strategy for emissions based regulation of landfill gas.

The Environment Agency (the Agency) is responsible for the regulation of landfill sites in England and Wales. Since its formation, the Agency’s regulatory strategy for landfill gas has been to require operators to demonstrate best practice. However, this approach does not allow environmental outcomes from site-specific landfill gas management to be easily illustrated or quantified. Greater clarity is now given to these environmental outcomes by augmenting best practice regulation of landfill gas with emissions-based regulation. This will require a “step change” in the management of landfill gas. However, it will enable the operator and regulator alike to respond to public concerns regarding landfill gas, including increasingly complicated health- related

A fugacity approach for generating a landfill gas trace component source term.

The quality of risk assessment output is determined by the input data used in environmental distribution, dispersion and exposure models. Whilst recent focus has been on the development of regulatory exposure assessment models for landfills, risk analysts are keenly aware of the need for improved source term models in order to improve confidence in risk assessments and allow better targeting of risk management actions. This research sought to reconcile measured concentrations of selected priority trace components in landfill gas with potential source term loadings that could be generated within landfilled waste. A fugacity approach estimated the loadings of four priority trace components required to generate the source-term for landfill gas risk assessment models; vinyl chloride (chloroethene), benzene, 1,3- butadiene and trichloroethylene. Three fugacity models, coded originally for soils, were adapted for an evaluative landfill environment, developed using data from the Brogborough (UK) test cells. Modelled concentrations were within the range of those observed in the field

Evaluating fugacity models for trace components in landfill gas.

A fugacity approach was evaluated to reconcile loadings of vinyl chloride (chloroethene), benzene, 1,3-butadiene and trichloroethylene in waste with concentrations observed in landfill gas monitoring studies. An evaluative environment derived from fictitious but realistic properties such as volume, composition, and temperature, constructed with data from the Brogborough landfill (UK) test cells was used to test a fugacity approach to generating the source term for use in landfill gas risk assessment models (e.g. GasSim). SOILVE, a dynamic Level II model adapted here for landfills, showed greatest utility for benzene and 1,3-butadiene, modelled under anaerobic conditions over a 10 year simulation. Modelled concentrations of these components (95 300 μg m−3; 43 μg m−3) fell within measured ranges observed in gas from landfills (24 300–180 000 μg m−3; 20–70 μg m−3). This study highlights the need (i) for representative and time-referenced biotransformation data; (ii) to evaluate the partitioning characteristics of organic matter within waste systems and (iii) for a better understanding of the role that gas extraction rate (flux) plays in producing trace component concentration

Estimating Pollutant Removal Requirements for Landfills in the UK: II. Model Development

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 requ

Estimating Pollutant Removal Requirements for Landfills in the UK: I. Benchmark Study and Characteristics of Waste Treatment Technologies

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 inadeq

Government, trusts, and the making of better roads in early nineteenth century England and Wales

This paper introduces new data to explain which actors developed better roads in early 19th century England and Wales. We find that central Government sponsorship and financing of new roads was limited to 100 miles on sections of the politically important London-Holyhead Road. By comparison non-profits, known as turnpike trusts, made thirty times more new road mileage by attracting capable surveyors and both public and private capital. Although the London-Holyhead Road had the highest quality, most turnpike roads were good. By Government working with and through trusts a better road network developed, especially in industrializing areas and along Mail routes.Leverhulme Trust. National Science Foundation (US)