Until recently so-called fugitive emissions from petroleum refineries, chemical plants and oil and gas production facilities have been under the radar as far as regulation is concerned. Fugitive emissions are small releases of greenhouse gases, air pollutants and volatile compounds from a large number of leak sources widely distributed over a facility, such as pipes, valves, pumps and storage tanks. As well as fugitive emissions some facilities also have process vents that release gases during normal operation but are not large enough to be monitored. Because there are so many of these small point sources total fugitive emissions can be significant and the costs of reducing fugitive emissions is generally low compared to other emission control technologies – some even argue profitable because the leaking products can be conserved and sold.
The stumbling block is the cost of detecting and quantifying fugitive emissions. Current measurement technology – hand-held “sniffers” – only work in close proximity to a leak and are not able to quantify the size of the leak. Inaccessible leaks, such as leaks from pipework suspended at height can go undetected for a long time. Fixing the leaks is usually a simple task, involving basic maintenance procedures that can be carried out without affecting production or scheduled for the next plant shutdown. Studies have shown that 75 percent of total fugitive emissions can be eliminated by fixing a small percentage of the biggest leaks.
Because of the measurement problem, estimates of fugitive emissions are calculated by counting the number of potential sources on a facility and using standard emission factors based on studies of leak rates at typical facilities.This method takes no account of actual leak rates at the facility in question, which could be higher or lower than average, and means that there is no incentive to reduce leaks because they will not be reflected in reported emission estimates. Because of the practical difficulties of actually measuring fugutive emissions it becomes impossible to regulate them – which is unfortunate because reducing fugitive emissions could result in a significant amount of low cost emission reductions. Leaks of unburnt gases such as methane are 21 times more damaging to the climate than when they are burned as a fuel.
Now a new technology is on the horizon that could change all this. The technology is called DIAL (differential absorption light detection and ranging) and uses lasers to sweep the sky downwind of a facility. The lazers detect all the gases in the air and quantify the amounts of each type of gas. According to the trials fugitive emissions measured by this technology could be over 9 times more than previously reported using the emission-factor approach. If true this could cause a complete re-think of fugitive emissions. At the moment the technology is way to expensive to deploy on a widespread basis. Because emissions vary from hour to hour and day to day, regular or constant measurement is required year round to reliably detect and quantify actual emissions. Maybe one day this will be possible. In the mean time this excellent opportunity to reduce emissions will probably remain under-utilized.
