(74d) Underestimated Emissions Inventories

A number of studies in the U.S. and Europe indicate that there are substantial errors in emission inventories of volatile organic compounds (VOCs) for refineries and chemical plants. Although significant reductions of VOCs have occurred over the past three decades, some reports suggest that emissions are underestimated by an order of magnitude or more. There are technologies used mainly in Europe that can provide substantially improved emissions inventories measuring VOCs with remote sensing tools instead of the current practices that are based on engineering estimation techniques. In Europe Differential Absorption LIDAR (DIAL) and Solar Occultation Flux (SOF) have been used to find leaks and identify substantial discrepancies in emissions inventories for over 20 years. Similar results have also been found during two field studies performed in Houston in 2000 and again in 2006 using air samples taken by airplanes and by the same SOF instrumentation used in Europe. It should be noted that the reported NOx emissions were reasonably close to the measured NOx in the Houston studies, which has been attributed to the use of continuous emissions measurement devices on most large NOx sources. This report will provide the studies performed to date, including the methods used to determine the VOC emissions.