Although the amount of methane emitted into the atmosphere by humans is far less than the amount of carbon dioxide released, it is a significantly more effective greenhouse gas, methane, which has a warming effect of about 84 times that of carbon dioxide within 20 years. Some people believe that methane emissions contribute 25% of the anthropogenic global warming effect.
The new study aims to add some urgently needed objective measurements of methane emissions that have not been fully studied: industrial users of natural gas. Most previous studies have examined methane emissions at early stages of the natural gas supply chain, including production and distribution point measurements. Methane emissions are also being effectively tracked in residential and commercial areas.
To explore methane emissions from users of the natural gas industry, researchers recently installed new methane sensors on some Google Street View cars. Fertilizer factories have been targeted because they are major users of natural gas, and six representative factories have been selected from about twenty in the United States. Vehicles equipped with sensors travel on public roads near factories to quantify methane emissions due to leakage, incomplete combustion or inefficient chemical reactions during fertilizer production.
The results are incredible. On average, 0.34% of the natural gas used by factories is leaked into the atmosphere. The study then extended this figure to all fertilizer production in the United States, calculating annual methane emissions of 28 gigagram. It is reported that the industry only estimates its methane emissions at 0.2 gigagram per year. EPA currently claims that all industrial processes and products used in the United States generate a total of 8 gigagram of methane emissions.
"We took a small industry that most people had never heard of and found that its methane emissions were three times those of all industrial production in the United States," said John Albertson, co-author of the study. "It shows us that there is a huge gap between prior estimates and actual measurements."
John Albertson said that recently natural gas has been an environmentally friendly alternative to traditional "dirty fossil fuels", so tracking methane emissions is crucial.
"... Methane is a major component of natural gas and has a greater potential for global warming than carbon dioxide," Albertson said. "There are massive emissions or leaks anywhere in the supply chain, which may make natural gas an important factor in climate change."
The study was published in the Journal Elementa.