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  Contact: Charlie Osolin
  Phone: (925) 422-8367
  E-mail: osolin1@llnl.gov
  October 14, 2005
SF-05-10-01

Everything counts: the multiple
paths to a carbon-free energy future

John Ziagos With Energy Flow Chart
Livermore environmental scientist John Ziagos with the Laboratory's interactive U.S. Energy Flow Chart. (Click here to download a high-resolution image.)

Here’s a quick quiz for energy planners, policymakers and investors:

Which of the following will enable the United States to eliminate manmade emissions of climate-changing carbon dioxide by 2050?

  1. Replacing petroleum with hydrogen to fuel all motor vehicles and aircraft.
  2. Replacing coal and natural gas with renewable energy sources to generate the nation’s electricity.
  3. Building 270 new nuclear power plants.
  4. Using heat pumps and solar panels for residential and commercial heating and cooling.
  5. All of the above – and then some!

According to the latest long-term energy use and carbon emissions projections by researchers at Lawrence Livermore National Laboratory (LLNL), the correct answer is number 5.

“Our projections show that no one technology, and not even a combination of all the known technologies massively deployed, as well as aggressive efficiency and fuel economy improvements, can stabilize U.S. carbon emissions between now and 2050,” says LLNL environmental scientist John Ziagos. “If we want to move toward a carbonless future, no single technology will do – everything counts.”

Livermore has been charting the nation’s energy production and use since 1975. The Laboratory’s “U.S. energy flow charts,” based on projections by the U.S. Department of Energy’s Energy Information Administration and other data sources, track energy trends, supplies and demand – electrical generation, residential and commercial heating and industrial and transportation uses. The charts were recently automated to illustrate the implications of various “what-if” scenarios of energy supply, efficiency and demand.

Reflecting the growing concerns about the effect of heat-trapping carbon emissions on the Earth’s climate, Livermore began calculating the “carbon flow” associated with different energy sources and demand scenarios – and discovered that even more than optimistic technology and efficiency assumptions are needed to eliminate increased carbon emissions resulting from the nation’s energy systems by 2050.

2050 Energy Flow Chart - Best Case Scenario
A “low-carbon” U.S. Energy Flow Chart for 2050, in which hydrogen produced by coal, renewables and nuclear power replaces oil to fuel the transportation sector, and much – but not all – of the carbon from burning fossil fuels is captured and stored underground.

“We started out by looking at the effect on carbon of switching cars from gasoline to hydrogen fuel,” said Ziagos, deputy head of LLNL’s Atmospheric, Earth and Energy Department. “We found that it’s going to take a lot more than hydrogen cars to reduce our petroleum dependence and carbon emissions below present levels.

“Autos will make up only one-third of the transportation sector, and transportation, even with hybrids, is only one-third of the carbon problem,” Ziagos said. “So even if every U.S. car in 2050 were to be powered by hydrogen, it would only offset about one-ninth of the total carbon emissions.”

The researchers then began plugging other “stretch” scenarios into the model to measure their potential effect on carbon emissions:

  • All transportation, not just cars (airplanes, freight, boats, trains), running on hydrogen produced by non-carbon-emitting sources, with light-duty vehicles averaging 50 mpg
  • Six new nuclear power plants going on line each year between now and 2050
  • Renewable energy sources (solar, wind, biomass, geothermal, hydroelectric) generating 75 percent of the nation’s electricity
  • Coal used exclusively to produce hydrogen instead of electricity, making possible the capture and storage in the earth of 2.3 billion tons of carbon dioxide a year.

Even in such a utopian energy economy, the chart shows, the nation would still be venting 2.3 billion tons of carbon dioxide a year – down from the current level of nearly six billion tons, but still a long way from carbon free.

The main reason: energy demand. Current government projections do not foresee substantial increases in efficiency; so by 2025 the rising demand for coal and oil to power the anticipated growth in electricity use and transportation will require an annual energy flow of about 133 quads (quadrillion BTU). That’s up from about 100 quads today, and would increase CO² emissions to more than eight billion tons a year.

If those trends were to continue unabated until 2050, Livermore’s charts show, energy demand would top 180 quads a year, U.S. petroleum consumption would double to 40 million barrels a day, and natural gas usage would soar from about 25 trillion cubic feet (TCF) today to more than 45 TCF in 2050 (one TCF equals about one quad).

“That’s hardly a realistic scenario,” says Ziagos. “Not only would we not want to become that dependent on foreign oil from a national security perspective, but venting that much carbon into the atmosphere could pose a threat to the planet from global warming.”

Chart Showing 2050 Carbon Emissions Under Low-Carbon Scenario
According to the LLNL “low-carbon” energy scenario for 2050, 2.3 billion tons of carbon dioxide would be captured and stored (CCS), but another 2.3 billion tons would be vented into the atmosphere and contribute to human-caused global climate change.

Many scientists warn that carbon dioxide, methane and other greenhouse gases, which trap heat near the Earth’s surface, are causing climate changes that could result in rising sea levels, the disruption of water supplies and crop and forest patterns, and extreme weather that could endanger both humans and wildlife. While some greenhouse gases arise from natural sources, there is a growing consensus that the planet is heating up due in part to manmade emissions, mostly from energy production.

“A more reasonable outlook for 2050 would have to include an aggressive push for improved energy efficiency, letting us cut consumption to about 120 quads per year,” Ziagos said. Required: a 50 percent improvement in electric generation, industrial, freight and aircraft efficiency; auto fuel economy averaging 50 miles a gallon; and petroleum consumption holding steady at about 22 million barrels a day. That scenario would restrain carbon emissions at the levels currently projected for 2025 – about five billion tons a year, assuming the capture and storage of about two billion tons of carbon dioxide.

But to reach the steep reductions in carbon emissions that may be needed to head off global warming, Ziagos said, the nation will need to commit to even greater energy efficiency improvements, large-scale carbon capture and storage and aggressive programs to increase the use of nuclear power, renewables and hydrogen. One key element in such a program would be eliminating the use of oil as a transportation fuel and replacing it with hydrogen generated largely by coal, which would no longer be used to produce electricity.

“Even in this case,” Ziagos said, “we’d still have about two gigatons of carbon dioxide going into the atmosphere every year. So if you ask me what it would take to achieve a carbonless future, I’d have to say at this point, you can’t get there from here. The vented carbon dioxide in 2050 is in the residential, commercial and industrial natural-gas-heating usage sector, and would require massive building heating and cooling changes. However, it’s probably going to take a transformational technology to totally eliminate carbon emissions from U.S. energy production.”

Nevertheless, Ziagos remains confident that scientific and engineering ingenuity will carry the day. Livermore and other national laboratory researchers are pursuing a wide variety of technologies, from innovative hydrogen storage to achieve a 500-mile-range car to developing new high-efficiency low-emission engines that can use diverse biofuels. Livermore is supporting the new international experimental fusion reactor known as ITER while also continuing to pursue alternative approaches to fusion, including the use of “magnetic mirrors” and high-powered lasers to attempt to capture the virtually unlimited, pollution-free energy that powers the sun and stars.

Greater use of geothermal and biomass energy than assumed in the LLNL chart might bring 2050 emissions down to one billion tons a year, Ziagos said, while an all-out commitment to solar could conceivably push CO² emissions down even more significantly.

“While pushing on all these fronts, we should pay close attention to how current technologies might work together to assure that all the aspects of energy use are addressed comprehensively,” he said. “Let’s see where the technology takes us.”



Founded in 1952, Lawrence Livermore National Laboratory is a national security laboratory that develops science and engineering technology and provides innovative solutions to our nation's most important challenges. Lawrence Livermore National Laboratory is managed by Lawrence Livermore National Security, LLC for the U.S. Department of Energy's National Nuclear Security Administration.