Case Study
Landfill Gas Case Studies: Research
Small Scale Study for Developing Design and Monitoring Specifications for Landfill Gas FLares
Enviros was contracted by the Ireland Environmental Protection Agency to carry out a literature review to meet three specific objectives.
Objective 1:
To review the emission limit values that are achievable in landfill gas flares and existing monitoring requirements for landfill gas flares in the EPA waste licences.
Landfill gas flaring installations currently operational in Ireland are reviewed. Monitoring results, and the limitations of assessing them for licence compliance are discussed. Concerns regarding flare emission monitoring are outlined.
Objective 2:
To propose an approach that the Agency can adopt to ensure that emissions from flares are controlled.
An overview of typical flare emissions and flare design aspects that govern the emissions discharged to atmosphere is provided. Sampling the inlet gas composition to assess likely emission concentrations after combustion, is discussed.
Objective 3:
To review the approach taken internationally by licensing authorities towards controlling emissions from landfill gas flares by design specification only.
International approaches to regulating emissions from landfill gas flares are reviewed. Discussions with the German Ministry for the Environment and other experts in the field of landfill gas control, are detailed.
Conclusions
The study provides an overview of the main issues surrounding landfill gas flaring, and outlines the principal considerations with regard to flare technology, operation and maintenance.
It concludes that extractive emissions sampling does not generally provide consistent results that can be used for Licence compliance assessment, primarily because of the fundamental design and operating characteristics of enclosed landfill gas flares.
International experience has shown a trend by regulation authorities towards the control of design specifications and a combustion temperature ~1000°C, with a minimum retention time of 0.3 seconds, rather than reliance on exit emission monitoring.
A regulation strategy based on inlet gas monitoring and design certification is proposed. This strategy would have the advantage of removing the need for potentially hazardous sampling of very hot emissions and the attendant difficulties of consistent sampling and analysis. Design features that should be included in enclosed flares and could form part of the operational verification or certification process are detailed in the study. More stringent exit emission monitoring requirements specified by the EPA would remain an option for non-certified flare stacks.
