Geoscientists at Newcastle University in the United Kingdom have recently confirmed that the Earth’s atmosphere switched back and forth from being hydrocarbon-rich and hydrocarbon-free- causing the atmosphere to become hazy and clear- repeatedly more than 2.5 billion years ago, during the mid-Precambrian supereon.

The alternation of haziness, resulting from microbial activity (intense enough to effect the Earth’s climate) that produced the hydrocarbons, occurred before the event in which the atmosphere underwent oxygenation- when oxygen became the principal element in the atmosphere- and sometime after the time when methane comprised much of the air.

The geoscientists analyzed marine sediments deposited 2.65 to 2.5 billion years ago in South Africa. They discovered the fossils of local microbes that produced oxygen. But if oxygen was present at the time these microbes existed, where could they have gone? The geoscientists also found carbon and sulphur isotopes, signifying that hardly any oxygen went into the atmosphere and instead stayed in the ground. It was then they ascertained that the atmosphere had not one state, but two, during which a transition took place.

“Instead of evidence for a continuously ‘hazy’ period we found the signal flipped on and off, in response to microbial activity,” Dr. Aubrey Zerkle states in the Newcastle University press release. Dr. Zerkle led the study and is a part of the School of Civil Engineering and Geosciences at Newcastle University.

“This provides us with insight into Earth’s surface environment prior to oxygenation of the planet, and confirms the importance of methane gas in regulating the early atmosphere.”

The geoscientists believe that it took so long for oxygen to dominate the atmosphere because the hydrocarbon haze blocked sunlight, affecting the evolution of microbes that depended on light to photosynthesize. Furthermore, when the amount of hydrocarbons decreased, the amount of methane (which dominated the atmosphere before the haze and haze-free switching) increased. Hence, oxygenation was delayed no matter the concentration of hydrocarbons in the atmosphere.

Evidence for the switch was further supported by models that demonstrated the transitions in action, which came from the NASA Astrobiology Institute, led by Dr. Mark Claire and Dr. Shawn Domagal-Goldman, with whom the geochemists collaborated. These models specifically showed “how the transitions could be caused by changes in the rate of methane production by microbes.”

“[These] models have [also] previously suggested that the Earth’s early atmosphere could have been warmed by a layer of organic haze,” Dr. Zerkle continues.

This discovery has changed aspects of how we come to understand the evolution of Earth and of early life, mainly of how the Earth’s atmosphere went from consisting of methane to oxygen- a concept that made scientists stumble for years.

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Research from SRI International has identified a promising new way to produce liquid transportation fuels from coal without consuming water or generating carbon dioxide. Based on data from bench-scale tests, SRI engineers estimate that the capital cost for a full-scale plant using SRI’s process would be less than half that of a conventional coal-to-liquids plant that uses a process called Fischer-Tropsch synthesis. FTS produces only a small fraction of the hydrocarbons needed for fuel and requires extensive recycling.

SRI’s new process uses natural gas to provide the hydrogen needed to convert coal to syngas (a mixture of carbon monoxide and hydrogen). Syngas is first converted into methanol, which can then be efficiently processed to make transportation fuels.

Using natural gas eliminates the need to add water as a source of hydrogen, reduces the need to add energy to drive the gasification reaction, and results in the use of a smaller gasifier. In conventional CTL approaches, energy is supplied by burning a portion of the coal feed, which then produces carbon dioxide. SRI’s approach makes it economical to use carbon neutral electricity, such as nuclear, hydro, or solar as a source of additional energy.

“The implications of this research are expansive, including enhancing U.S. energy security through the use of domestic carbon sources,” said Robert Wilson, Ph.D., director, Chemical Science and Technology Laboratory, SRI International. “The process can also dramatically reduce the environmental footprint associated with alternative transportation fuels.”

SRI performed a series of analyses to examine the environmental impact of the technology under several scenarios. Based on these analyses, if diesel were produced using biogas as the source of methane, the resulting product would qualify as an alternative fuel under the revised Renewable Fuels Standard of the Energy Independence and Security Act of 2007. The Act requires alternative fuels to meet a standard of 50 percent reduction of greenhouse gas emissions compared to other fuels.

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