Is natural gas a 'bridge' to a hotter future?

December 8, 2014
A natural gas plant in Moss Landing, California, courtesy of Carnegie President Matthew Scott. Credit: Carnegie President Matthew Scott

Natural gas power plants produce substantial amounts of gases that lead to global warming. Replacing old coal-fired power plants with new natural gas plants could cause climate damage to increase over the next decades, unless their methane leakage rates are very low and the new power plants are very efficient.

These are the principal findings of new research from Carnegie's Ken Caldeira and Xiaochun Zhang, and Nathan Myhrvold of Intellectual Ventures that compares the temperature increases caused by different kinds of and natural gas . Their work is published in Environmental Research Letters.

There is an ongoing debate among people concerned with power plants and the future of energy policy and greenhouse gas emissions. Does it makes sense to replace old coal-fired power plants with new natural today, as a bridge to a longer-term transition toward near zero-emission energy generation technologies such as solar, wind, or nuclear power? A key issue in considering the decision has been the potential climate effects of natural gas versus coal. Studies have yielded different results by focusing on power plants with different characteristics and using different definitions of what it means to be "better" for climate.

Carnegie's Caldeira and Zhang, along with Myhrvold, aimed to identify the key factors that are responsible for most of the difference in greenhouse gas emissions between individual gas and . The key factors, they found, are power plant efficiency and, in the case of natural gas plants, methane leakage during the supply process. They used these factors to derive a simple model for resulting temperature change caused by the carbon dioxide and methane released by a particular plant.

The team chose a simple and understandable way to compare climate effects of different types of power plants. They predicted how much global warming would be produced by different kinds of power plants during and after their period of operation.

A comparison of the best natural gas plant with the typical coal plant, courtesy of Ken Caldeira. Credit: Carnegie's Ken Caldeira

They found that because natural gas plants are overall more efficient than coal plants, producing more energy per unit of carbon, they could cause less warming in the long term. However, it all depends on the amount of methane leakage that occurs. Natural gas plants that leak a substantial amount of methane during their supply process can produce more warming than comparable coal plants.

A second comparison of the typical natural gas plant with the typical coal plant, courtesy of Ken Caldeira. Credit: Carnegie's Ken Caldeira

"If there is substantial natural gas leakage, then building new natural gas plants would lead to more near term climate damage than using the old dirty coal plants," explained Caldeira. "But natural gas plants would help reduce other types of air pollution that damage our health, and would be somewhat better for climate in the long term."

If faced with the choice of shutting down either a typical coal plant or a typical gas plant and methane leakage from the natural gas plant is below about 2 percent of total fuel, there would be a short-term climate benefit to shutting down the coal plant instead of the natural gas plant, the team found. But if methane leakage would be greater than 2 percent, there would be less warming in the near term if the natural gas plant were shut down instead of the coal plant.

Regardless, the team emphasized that meeting upcoming targets will require deeper emissions cuts than just building with low . If is to be a part of a future near-zero emission energy economy, methods for capturing and storing carbon from gas-fired power plants will likely be necessary.

Explore further: Replacing coal and oil with natural gas will not help fight global warming

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2.3 / 5 (3) Dec 08, 2014
The future is going to be whatever the ruling elite says it is. We have always been at war with Eastasia.
2.3 / 5 (3) Dec 08, 2014
The pic is of Units Six and Seven at Moss. They are super-critical monotubes, running cross-compound turbines with multiple reheats. At about a million kW each, (utilities call it 1000 Megawatts), they have been workhorses of PG&E. I stood in the firebox on Unit Seven on a school field trip once. It is huge.

And, yes, the operating conditions are determined by metallurgy, a fact disputed by a denier who knows nothing about generating plants.

But we will probably have to turn gas to feedstocks for hydrogen and plastics and lubricants.
1 / 5 (4) Dec 08, 2014
Assuming that methane and CO2 actually have as significant an impact on warming as some climate scientists predict (which is overstated, see below), the EPA data for the U.S. shows methane emissions (and CO2 emissions) decreasing even as more natural gas power plants are being built:

CO2: http://www.epa.go...co2.html

So apparently U.S. natural gas fueled power plants don't leak much methane because emissions have gone down over the last several years. Chances are they will become even more efficient in the future.

As for how much warming "greenhouse gases" cause, the IPCC's latest report shows predictions of warming are significantly overstated. See this graph:


It's likely that this report's conclusions are also overstated.
1 / 5 (3) Dec 08, 2014
Another study that doesn't do or prove anything. So sad what 'science' is called in the United States.

Of course this is all based on piss poor assumptions. Why would we assume that power plants don't improve in operational efficiency and reduces leakage? Oh wait...that doesn't fit the objective of the 'study'
3 / 5 (4) Dec 08, 2014
Did Ago not see the mention of: "methane leakage during the supply process"?
1 / 5 (1) Dec 08, 2014
Yes, coal is hazardous to mine, costly to transport, and generates fine respirable ash containing trace heavy metals. But the Sierra Club has no answer for the small coal-burning cooking fires spread across India and many developing nations as well as their need for reliable electricity. Let's thrust these billions of people back into dark subsistence living. All European nations, including Germany, are finally walking away from the massive government subsidies to prop up wind and solar. CO2 causing Global Warming is a First World conceit. Start talking to INDEPENDENT geoscientists and the variable geothermal heat coming from within the planet, as well as all the simple molecules generated to support life -- Abiotic Methane, etc. See
1 / 5 (2) Dec 08, 2014
"But the Sierra Club has no answer for the small coal-burning cooking fires spread across India and many developing nations as well as their need for reliable electricity."

This is hilarious. Did he make it up himself?

Gobar and other gas digesters are freeing Indian women from the choking smoke of fires, where they are used. And PV is providing light to villages which never had it.

Alternative technologies are perfect for developing nations, and EF Schumacher would be pleased to see his thesis proven.
1 / 5 (2) Dec 09, 2014
"All European nations, including Germany, are finally walking away from the massive government subsidies to prop up wind and solar."
A major German utility is splitting off its conventional coal and nuclear business to try to unload it onto others, while they keep the renewables themselves.
not rated yet Dec 13, 2014
Someone please tell me where plants are leaking methane from. Yea, I saw it say in the supply process too but what the heck does is that supposed to actually mean? I delivered propane both bottle and bulk at one time and any leak however small was fixed immediately. Very little was leaked when connecting or disconnecting the bulk hose and I'm sure modern tankers are not going to blasting gas in the air either so where are all these supply leaks coming from. Anyone got any ideas?

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