Steve Last

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How to Achieve Good Landfill Gas Control: from an EU Perspective

What are the main reasons for providing effective landfill gas management, and issues which result?

There are several and these are:-

1. Removal of significant risk of explosion or fire
2. Minimising global environment effects
3. Long term commitment of staff and resources
4. Costs for labour, transport, equipment, sampling
5. Indirect benefits and dis-benefits of good control

1. Explosion and Fire Hazards

The first and obvious advantage of good management of landfill gas, is the removal of any significant risk to persons or property from ingress by flammable gas to property or services. As well as the prevention of the obvious gas explosion or fire hazard, this should also include the prevention of vegetation damage and die-back.

It has to be accepted that no-one can give an absolute guarantee that no explosion or other gas incident will occur, but the standards of management required in the EU ATEX Directive reduces the risk of an occurrence to an acceptable level. In the United Kingdom the ATEX Directive is regulated with the DSEAR (Dangerous Atmospheres and Explosive Atmospheres Regulations), each EU nation will have its own national regulations to enforce the ATEX Directive.

In order to ensure the lowest risk of explosion as required by the Directive the operators will need to follow all the advice contained within the EU ATEX Directive.

Thus at all modern landfill sites a gas pumping system is essential, with commercial utilization to prevent underground gas migration. All pumped gas must then be burnt in flares or gas engines or gas turbines to minimise the greenhouse gas effect of those emissions.

The wells and the boreholes outside the wastes in the adjoining strata should be regularly monitored.

Where the risk is considered highest as indicated by the geology and groundwater levels, monitoring system alarms is necessary within buildings.

All the continuous site monitoring will need to be supported by periodic confirmatory analysis by the use of separate hand-held and fully laboratory calibrated sensors.

A surface and subsurface investigation may also be necessary possibly once or twice per annum when you have underground services at risk or where the strata is fissured and it is not possible to guarantee that all fissuring has been intercepted by boreholes or other probes.

2. Global Environment Effects

The approach described above will not only reduce the risk of an uncontrolled ignition of methane, but also significantly reduce the amount of methane passing into the atmosphere. It can also provide a "free" energy source which will provide some conservation of other energy resources.

3. Long-term Implications

The operator is likely to have this continuing commitment to a site for over 15 years and possibly for as long as 50 years, or even 150 years. For the whole time, access to the control system will be essential for monitoring, adjustment of valves, and maintenance.

The gas wells, pipelines and the necessary enclosure for the pump and flare stack will therefore restrict land usage.

Around the site, access will be necessary to all monitoring boreholes and any monitoring points within services or buildings for most of the time that the site is actively gassing. However it will be impossible to determine, with any degree of accuracy, how long the monitoring outside the wastes will be necessary and one should therefore be pessimistic in quantifying any time scale.

The system will need regular attention which will involve visits to the site and inspection of the whole area of the site and its environs.

The control measures may need total replacement every 10 to 15 years, depending factors such as settlement, leachate control, design and installation of wells etc.

4. Costs

Good landfill gas management has both capital and significant running costs, no matter what type of monitoring regime is adopted.

Capital Costs:

The installation of sufficient control wells, pumping equipment and flare stack, coupled with the necessary monitoring boreholes will require a large capital outlay, which will be dependant on the size of the site and the risk assessment.

During the gas evolution phase, additional wells or boreholes may need to be drilled because of physical changes occurring in or around the site.

Running Costs:

There are a number of cost centres which need to be considered.

These are:

Labour;

Even the most sophisticated system of monitoring and control cannot escape regular visits to sites to ensure satisfactory control, there is no alternative to periodic examination of the site and its surroundings, to ensure satisfactory gas control.

More basic systems without automatic controls could entail one or more trained operative visiting a site one day per week.

Equipment;

All equipment needs periodic examination and maintenance and in the long time-scales, some replacement.

Sampling;

As well as monitoring with portable instruments, there will be a need for periodic laboratory analysis, especially where certain types of instruments are used or where landfill gas is utilized.

Transport;

National operators with former landfills in different parts of the country will need to move monitoring teams and equipment from one site to another fairly quickly, which bears a cost burden for transport.

Waste Regulatory Authorities (WRAs) will need mobile teams to travel around both operational and closed sites to undertake their functions under the to ensure that gas control is correctly carried out all appropriate landfills.

Other factors;

Whilst operational and maintenance costs of the system can be offset by utilization, it is important that all commercial landfill projects are set up with business plans from the outset which will ensure that the income to the business (gate fee) is adequately high to pay back the total cost for environmental control.

It is important the WRAs ensure within their regulatory remit that the commercial landfill site operators place in trust adequate funds for the afterlife care of their landfills.

When considering a single site the impact of monitoring and control of landfill gas does not seem a tremendous burden. Total costs in the normally vary from USD20,000 to USD200,000 per annum depending on the size and depth of the site and its risk assessment. However when one considers that in some EU Counties there are very many former landfill sites requiring monitoring, and a significant percentage of these needing control measures, it can be seen that the cost implications are very significant in certain areas.

The National Government Departments responsible may need to provide supplementary funding available to meet much of the historical un-engineered gassing landfill site costs.

5. Benefits and Dis-benefits of Good Landfill Gas Management

There are indirect benefits to good management of gas. The most important of these are:

1  The restoration of previously derelict land for better use for the community
2  Provision of former sites for agricultural or leisure activities
3 Good restoration coupled with gas management will make a former site become an environmentally acceptable neighbour.

However, the essential visits to closed sites, without tact and discretion could become a possible nuisance to the occupiers of property on or adjacent to the site.

Conclusion

Good monitoring and management, as described in this articles and supported by the standards given in the revised EU ATEX Directive, will provide a sound platform for WRAs to prevent future problems due to landfill gas from operational sites and for WRAs to deal with former sites which have not been properly controlled in the past.

Good standards of gas management, which should follow, will improve the public acceptability of landfill sites. However it is agreed that there is a need for further research, which should lead to better standards of gas management, especially where sites only produce a poor quality of landfill gas with a low methane content, making it impossible, at present to generate power from those sites.

Contact Steve Last by using the “Contact Us” page form on this web site if you require any LANDFILL GAS MANAGEMENT assistance, and have a project in mind for which we can quote prices for you.

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