Researchers from Cornell University and Environmental Defense Fund have discovered that emissions of methane from the industrial sector have been vastly underestimated. They applied the use of a Google Street View car stocked with a high-precision methane sensor to find out that methane emissions from ammonia fertilizer plants were 100 times higher than the fertilizer industry's self-reported estimate. Also, the emissions were substantially higher than the Environmental Protection Agency (EPA) estimate for all industrial processes in the United States.
Co-author of the study and professor of civil and environmental engineering, John Albertson, said that they took one small industry that most people have never heard of and found that methane emissions of this industry were three times higher than the EPA assumed was emitted by all industrial production in the United States. Albertson explained further that it shows that there's a massive gap between a priori estimates and real-world measurements.
The team published the results of the study in Elementa. In recent years, there is an increase in the way natural gas is used, bolstered by improved efficiency in shale gas extraction and the perception that natural gas is a less dirty fossil fuel.
Albertson said that natural gas is mostly methane, which molecule-per-molecule has a stronger global warming potential than carbon dioxide. The presence of significant leaks or emissions everywhere along the supply chain could make natural gas a more substantial contributor to climate change than previously thought.
For the emissions' assessment of methane from downstream industrial sources, the team focused on the fertilizer industry, which uses natural gas both as the fuel and one of the main ingredients for ammonia and urea products. Ammonia fertilizer is produced at only a couple dozen plants in U.S. factories are often located near public roadways where emissions carried downwind can be detected, in this care by mobile sensors.
For this study, the Google Street View car toured public roads close to six representative fertilizer plants in the country's midsection to quantify "fugitive methane emissions" defined as inadvertent losses of methane to the air possible because of deficient chemical reactions during fertilizer production, incomplete fuel combustion or leaks.
In their discovery, on average, 0.34 percent of the gas fuel used in the plants is emitted to the atmosphere. Mounting the rate of this emission from the six plants to the entire industry suggests total annual methane emissions of 28 gigagrams, 100 times higher than the fertilizer industry's self-reported estimate of 0.2 gigagrams per year. Also, this figure far exceeds the EPA's assessment that all industrial processes in the United States produce only eight gigagrams of methane emissions per year.
