A UN report published recently blames the cow for 18 per cent of the greenhouse gases that cause global warming – more than the combined contribution from cars, planes and all other forms of transport. Their flatulence and manure emit more than one third of methane emissions, which warms the world 23 times faster than carbon dioxide.
We visit many sites that produce methane from waste and generate power that is fed into the grid. Sometimes the most obvious sign that gas is being produced and burned is from the use of flares. Flaring is used to burn excess gas when the engines are not available to generate power and could be viewed as wasting a commodity. However, it is always preferable to have clean and efficient combustion and produce CO2 from a flare rather than risk releasing methane into the atmosphere.
The landfill, anaerobic digestion and waste water industries that generate combustible biogas, have the emissions from the flares permitted and controlled. During the commissioning phase, or if the flare is in regular use then there is generally a requirement to test the flare emissions. If the flare is used as a back up to other combustion plants, then the emission testing requirement is generally dependent on the operational hours (typically 876 annual hours’ usage).
Another industry that uses flaring is Fracking. Here it is used to burn the shale gas prior to it being captured and piped and also uses flaring as a safety release mechanism. Fracking differs from the industries above because the gas is not produced from waste. Rather than being in the region of 40% to 60% methane, the combustible content is closer to 100%. Usually when the flares are running for fracking, they cannot be switched off as it would create a major hazard both environmentally and from a health and safety point of view. Until recently there has been no possibility of monitoring from live flares and therefore no opportunity for fracking companies to prove how efficient their flares are.
A flare on a fracking site with 98% destruction efficiency burning close to 100% methane would crudely mean an emission of VOCs at around 20,000mg/m3 – this is approximately 2000 fold higher than standard emission limits for similar flares burning 40-60% methane on the types of sites mentioned above. Most flaring companies develop their flares to run more efficiently than this but until now we have had to rely on calculated destruction efficiencies to estimate the environmental impact of flaring for fracking.
For more information on Flaring, why not have a read of our White Paper entitled: “Flaring and the implications on pollution – focusing on biogas flaring from landfill, sewage and anaerobic digestion sites”.