Researchers at Pittsburgh's Carnegie Mellon University are raising doubts about the long-term effectiveness of liquefied natural gas (LNG) in meeting the nation's energy needs while reducing greenhouse gas (GHG) emissions, but an industry trade group claims their analysis is hopelessly flawed.

In the Sept. 1 edition of the journal "Environmental Science and Technology," Carnegie Mellon researchers Paulina Jaramillo, W. Michael Griffin and H. Scott Matthews purport to show that LNG imported from foreign countries and used for electricity generation could have 35% higher life-cycle greenhouse gas emissions than coal used in advanced power plant technologies.

"Investing in LNG infrastructure today could make sense if it helps moderate natural gas prices and keeps existing natural gas power plants running. But making this investment ultimately locks us into certain technologies that make it harder for us to change paths in an increasingly carbon-constrained world," said Matthews, an associate professor in Carnegie Mellon's Civil and Environmental Engineering Department.

The 1990s saw a surge in construction of natural gas-fired power plants, fueled by cheap natural gas, low investment requirements and the idea that gas was less carbon-intensive than coal. Since these plants were constructed, gas prices have skyrocketed as North American supply has become more limited. These gas plants are now operating at a very low capacity, fueling the energy industry's interest in increasing gas supply with LNG.

Those decisions are complicated by the fact that gas prices may stay high because of maturing North American gas fields. Gas production in North America has been flat or down in each of the past six years, according to the Energy Information Administration. Increasingly, domestic gas will be drawn from nontraditional and more expensive sources that require the development of more complex networks to extract and deliver it to the U.S. market.

However, the increased importation of LNG and all of its indirect impacts could eliminate the environmental benefits of gas over coal when future carbon mitigation technologies are adopted, the Carnegie Mellon team said.

The researchers point out that LNG has many indirect impacts compared to domestic gas. LNG is extracted in a foreign country, liquefied, put into a tanker to cross oceans, and then regasified and put into pipelines when it reaches the U.S. Each of these steps leads to indirect environmental impacts, such as carbon dioxide emissions from changing gas to liquid and back. In addition, the facilities and tankers necessary to liquefy, move and regasify the natural gas are not plentiful and those in the works will not be up and running for several years.

The Gasification Technologies Council (GTC) last week blasted the recent findings of the university researchers. GTC said it strongly challenges the findings of the paper published by Carnegie Mellon regarding life-cycle air emissions from state-of-the-art fossil-fueled energy technologies for power generation.

"The Carnegie Mellon paper cobbled together averaged and generic data from a variety of sources and made incorrect assumptions about substitute natural gas (SNG) and integrated gasification combined cycle (IGCC)," said GTC Executive Director Jim Childress. "As a result, its findings are nothing more than hypothesis and conjecture, and sadly miss the true benefits of gasification-based technologies."

GTC said the Carnegie Mellon study had "many flaws." Among them:

"The paper reveals a complete lack of understanding of gasification technologies and of the energy marketplace in which these processes operate," said Childress. "You can't use outdated figures, generic data, or bad information and then say you've got a report that accurately studies the life cycle emissions of SNG, IGCC or any other fuel. To suggest that SNG and IGCC plants would be dirtier than pulverized coal plants is to deny the reality of sound science and solid technology."

The Carnegie Mellon research team also argues that the U.S. shouldn't rush to invest large amounts in a new infrastructure, such as the LNG infrastructure, without analyzing all the indirect implications of those investments compared to alternative supply options. In addition, utilities and the government should put more effort into conservation and energy efficiency that could help reduce the need for large investments, it said.

"As the options grow more complicated, the choices become harder and harder," said Griffin. "We just want to make certain that all the choices -- and their impacts -- are understood.''

For more than 50 years, gasification has been used around the world by a range of industries to create a variety of high-value products, GTC said. SNG has been produced in the United States via gasification since the mid-1980s in North Dakota at a large-scale plant that has been capturing CO2 for enhanced oil recovery since 2000. IGCC plants are operating successfully in the U.S., Europe and Japan. Since 2004, China alone has started up 29 gasification facilities as one element of a national policy to reduce its dependence on imported petroleum for the production of chemicals and fertilizers.

GTC represents companies involved in the development and use of gasification technologies as well as engineering, construction, manufacture of equipment and production of synthesis gas by gasification. The organization's website is www.gasification.org.

The Carnegie Mellon research was funded by the U.S. National Science Foundation, the Teresa Heinz Fellows for Environmental Research, the Pennsylvania Infrastructure Technology Alliance and the Blue Moon Fund. The "Environmental Science and Technology" article on the research -- "Comparative Life-Cycle Air Emissions of Coal, Domestic Natural Gas, LNG, and SNG for Electricity Generation" -- is available from the publication's website, www.pubs.acs.org/journals/esthag/. Click on "current issue" or use the site's search function.

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