EME 444
Global Energy Enterprise

Looking Ahead


A Mixed Bag of Climate Benefits

From a climate change perspective, natural gas has some strong positive and negative aspects. One of the primary environmental benefits of natural gas is that it emits much less CO2 per MMBTU (million BTUs) than other fossil fuel sources. Much less, in fact, as can be seen in the chart below.

Pounds of CO2 emitted per million Btu's of energy by fuel type
Fuel Type Pounds of CO2
Coal (anthracite) 228.6
Coal (bituminous) 205.7
Coal (lignite) 215.4
Coal (subbituminous) 214.3
Diesel Fuel and Heating Oil 161.3
Gasoline 157.2
Propane 139.0
Natural Gas 117.0

As you can see, natural gas has the lowest carbon intensity of all fossil fuels, and emits about half as much CO2 per unit of energy as coal. Coal and natural gas are the two primary sources of electricity, and in addition to natural gas emitting less carbon dioxide on a raw energy basis, as mentioned previously combined cycle turbines are more efficient than coal-fired power plants, which decreases the carbon footprint further relative to coal in terms of pounds of CO2 per kWh generated.

The shale gas boom has been one of the drivers of the decreasing carbon intensity of the energy sector and the U.S. economy. There are five lines in the chart below, each of which indicate a relatively clear trend. Each of these lines shows a trend relative to 1990. For example, As of 2003, the GDP (the blue line at the top) increased to a factor of 1.5, which means the GDP was 50% larger in 2003 relative to 1990. (This chart is from the US EIA, and there are a number of excellent charts on the page if you are interested):

  • GDP (blue line at the top): "Total value of goods and services produced over a specific time period" (From Investopedia, a great source of economic/financial information, by the way!).
  • Energy CO2 (red line, second from top): These are the total emissions that were emitted as a result of energy use.
  • Carbon intensity of energy (yellow line, third from the top): This indicates the ratio of carbon dioxide emissions to energy consumed.
  • Energy intensity of the economy (green line, fourth from the top): Indicates the ratio of energy use to economic output.
  • Carbon intensity of the economy (brown line, bottom): Indicates the amount of CO2 emitted per unit of economic output.
Figuree 7.11: Trend in various indicators of energy-related emissions drivers
Click link to expand for a text description of Figure 7.11

Index of key energy related emissions drivers, 1990-2014. 1990 acts as a baseline labeled 1.0

  • Gross Domestic Product: increases fairly steadily with a slight dip in 2009, reaching about 1.9 in 2014
  • Energy CO2: increases slightly 1990-2009, then declines to about 1.1 in 2014
  • Carbon Intensity of the economy: steadily decreases to approximately .6 in 2014
  • Energy Intensity of the economy: Follows the same trend as carbon intensity of the economy
  • Carbon Intensity of the energy: fairly stable at 1 until 2007-2008, where it slightly decreases to .9 to 2014

The EIA attributes part of the decline in overall emissions and decreased carbon intensity of the economy and energy generation to natural gas usage.  However, natural gas can have (and has had) negative climate impacts.

To Read Now

The Future of Natural Gas

The following essays are from the Union of Concerned Scientists (UCS). The UCS is known as a strong proponent of renewable energy and energy efficiency, safe and clean energy supplies, and policies that address climate change. The essays appear at the same location on the same web page, but at two different points in time. The first essay was originally accessed in February 2014, and the second was last accessed in September 2017. The first essay thoughtfully draws together the vying promises and challenges of natural gas at a time when fracking was not quite as ubiquitous (the essay was written in 2010, as it turns out). The second essay was written in 2015. These positions illustrate both the promise of natural gas as a (possibly) lower-carbon "transition" fuel and, when taken together, the cautiousness with which societies should approach increased natural gas production... and give us a nice landing spot for this hard-working lesson. Enjoy.

The Future of Natural Gas

A convergence of factors is driving our society towards greater reliance on natural gas as a source of energy. An increased focus on the potential reductions in carbon emissions and air pollution from burning natural gas instead of coal or oil have made natural gas an environmentally attractive alternative to other fossil fuels. Concurrently, improved techniques for extracting unconventional sources of gas have dramatically raised estimates of the U.S.’s available gas resource.

Because energy produced from natural gas has much lower associated carbon emissions than these other fossil fuels, natural gas could act as a “bridge” fuel to a low-carbon energy future. Particularly in the electric sector, natural gas has the potential to ease our transition to renewable energy.

In the short term, renewable energy added to the grid may displace natural gas use, because natural gas power typically has the highest operating costs. In the long term, increased amounts of renewable energy are likely to encourage the use of natural gas as a complementary source of power. The integration of large amounts of renewable energy sources into the electrical generation mix will pose some challenges for the nation’s electric system because of the inherent variability of solar and wind power. Natural gas plants have the operational flexibility to vary their production rapidly, allowing them to provide reliability to the electric power system as it transitions to greater shares of renewable generation.

Natural gas is by no means a panacea for the environmental problems caused by our energy use. There is broad agreement among climate scientists that carbon reductions of about 80 percent will be needed to avert the worst effects of climate change, so simply switching to natural gas from coal and oil will not ultimately bring about the necessary reductions. In addition, the development of our newly-discovered shale gas resource will disturb areas previously untouched by oil and gas exploration and raise serious water management and quality challenges. Some researchers have also suggested that abundant shale gas resources could delay the transition to renewables by providing a cheap, plentiful alternative.[48] Given the competing uses of natural gas and the vagaries of regional supplies, increased dependence on natural gas also exposes our economy to its frequent price volatility.

Overall, the increased use of natural gas over coal and oil will produce real and substantial reductions in global warming emissions and improvements in public health. As gas use expands, the natural gas industry must also minimize the environmental effects of its extraction and production. If used wisely and efficiently, natural gas can help our economy effectively transition toward even cleaner, more sustainable sources of energy like wind, solar, geothermal, and bioenergy.

(Union of Concerned Scientists, retrieved February 2014).

The Future of Natural Gas

Despite significant environmental concerns associated with its extraction, production, and distribution, natural gas burns more cleanly than coal and oil and therefore offers advantages in reducing emissions and improving public health. However, natural gas is a fossil fuel whose emissions do contribute to global warming, making it a far less attractive climate solution than lower- and zero-carbon alternatives such as energy efficiency and renewable energy.

Furthermore, new research suggests that methane leakage during the extraction and distribution of natural gas may be undermining the potential to reduce global warming emissions by using natural gas in place of higher-carbon fossil fuels such as coal and oil. And new horizontal drilling and hydraulic fracturing (or "fracking") techniques that have allowed domestic gas and oil production to expand rapidly over the past decade have raised new questions about the impacts that natural gas extraction and use will have on climate change, public health and safety, land and water resources, and people. This expansion is currently outpacing our capacity to understand and manage the attendant risks.

During our nation's transition to a low-carbon energy future, natural gas can play an important but limited role in the electricity and transportation sectors -if policies sufficient to minimize emissions and protect communities and public health are put in place.

Union of Concerned Scientists, retrieved September 2017).