Masses of methane escape from Italy

Italy is the seventh largest European producer of natural gas, with reservoir volumes approaching 2200 billion cubic meters (2877 billion cubic yards). Of this, 74 percent formed through microbial decay of organic matter (biogenic gas), 14 percent formed by thermal breakdown of organic material at greater depth (thermogenic), and 12 percent is mixed. Because most gas fields occur in areas influenced by tectonics, gas migration to the surface is widespread, leading to over a thousand seeps, including mud volcanoes and dry seeps.

Etiope et al. assess the gas origin from all main seeps still active today. Noting that methane is a potent greenhouse gas, they seek to quantify its flux to the atmosphere, including contributions from diffuse soil degassing. They find that 80 percent of the seeps release thermogenic gas, and that mud volcano gas is generally lighter (more methane, less ethane and propane) than its original reservoir gas. Dry seeps, instead, maintain the same alkane composition as their reservoirs. The authors estimate that methane emission may reach levels of hundreds of thousands tons per year, comparable to national emissions from the fossil fuel industry.


Posted by: Sarah    Source