Introduction 
The operation and maintenance of landfill gas flares in Ireland varies significantly from site to site. Licence compliance assessment of flares based on stack emission monitoring results is not a satisfactory approach, as flare stack emission monitoring can seldom meet standardised monitoring protocols, as well as being extremely hazardous for monitoring personnel. This is due to the extreme temperatures of the stacks (~1000 °C) and the fluctuating volumetric flow encountered. There are also limitations of flare stack design and the presence of significant turbulence in stacks leading to non-uniform gas streams. 
Internationally, diverse approaches are being taken in the control and design of landfill gas flares, ranging from reliance on stack emission monitoring (UK) to control via strict design criteria (Germany, Netherlands and Switzerland). In the above European countries flare design criteria require manufacturers certification, ensuring that flares can meet combustion temperatures above 1000° C, and retention times of 0.3 seconds in the burner, as a means of effectively minimising emissions without undue reliance on flare stack monitoring.
In view of the fundamental difficulties inherent in extractive emissions sampling, and the feasibility of controlling the major flare emissions by system design as outlined in this small scale study, we consider a design certification and performance verification-based approach to be a preferred option for the control of emissions from flares.
Figure 1 - Candle Flare
Please note: This flare photograph was taken some years ago. open flare designs like this are not suitable for UK use. Only enclosed flares are allowed for permanent use in the UK.
Photo: Summerleaze Re-Generation Ltd
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