July 13, 2009

Iron and manganese used to convert methane

U.S. scientists say they have discovered marine microorganisms use manganese and iron to convert methane into carbon dioxide.

The Pennsylvania State University researchers said their finding is important because carbon dioxide can produce compounds that sequester carbon in the ocean, reducing the amount of CO2 in the Earth's atmosphere. That process had previously been thought to be dependent on compounds containing sulfur.

Graduate student Emily Beal, principal author of the study, said the scientists incubated samples of marine sediment taken from an 1,800-foot-deep site in the Pacific Ocean 20 miles off the California coast. Among the samples were those having sulfur compounds, and others that had iron oxide or manganese oxide.

In the empty space above the sediment, the researchers placed methane gas containing a non-radioactive carbon-13 isotope and later measured the amount of any carbon dioxide produced by the samples.

They found the sulfur compound produced the most carbon dioxide, but samples with iron and manganese also produced some of the gas.

People had speculated that iron and manganese could be used, but no one had shown that it occurred by incubating live organisms, said Beal.

The study appears in the journal Science.