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Photo Friday: Where does it come from? Where does it go? Visualizing Energy Flows

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Each year, Lawrence Livermore National Laboratory publishes a powerful graphic of U.S. energy use. In the most recent version, one can see how the ~97 quadrillion british-thermal units (quads) of energy used in the United States can be broken down by uses and sectors. This total consumption represnts a 2.4% increase in energy use compared to 2012 and is still slightly less than energy use in 2010.

Overall, just under 60% of primary energy resources were rejected, often as “waste heat.” Almost 92% of coal was used for electricity generation, with the remaining 8% being used directly by industry. As shown along the bottom of the chart, about 92% of the 27 quads used for transportation was supplied by petroleum.

Photo Credit: Lawrence Livermore National Laboratory (LLNL)

Melissa C. Lott About the Author: An engineer and researcher who works at the intersection of energy, environment, technology, and policy. Follow on Twitter @mclott.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. phalaris 1:40 pm 06/6/2014

    It shows us what we’re up against. Most of the debate on reducing C02 revolves around electricity generation, but as the chart shows, this is not half the story.

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  2. 2. Wayne Williamson 5:24 pm 06/12/2014

    I’m unsure from the graph but it looks like we waste 60 percent of the energy produced.
    I guess I would like to see the same graph for say 1953 and 1983.

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  3. 3. BullishOnEntropy 3:00 pm 06/30/2014

    phalaris, you make a good point, but it is worth considering CO2 emissions directly. LLNL puts out a similar flow diagram for CO2 (–though it’s worth noting this only appears to be the energy sector and does not include emissions from livestock, land use change, etc.

    You can see from the charts that electricity generation makes up 38% of the emissions, despite contributing only 32% of the energy services. This is for the same reason so much discussion centers on electricity–burning coal is incredibly carbon intensive, and it can be easily offset cost-effective by less carbon intensive natural gas and nearly zero-carbon renewables like solar and wind. Most of our coal plants are quite old, and competing technologies have never looked better.

    Another feature of note is how inefficient the transportation sector is as a whole–34% of energy-related emissions for only 15% of energy services. This is because we lug around mini power plants (internal combustion engines) in our vehicles–these engines are far less efficient than modern thermal power plants. This is another argument for electric vehicles–the powertrain of an EV is much more efficient than an ICE, so electrifying transportation with a low-coal electricity system makes environmental sense.

    Of course other sources of CO2 are important as well–”land use change” (read: deforestation) and livestock among them. All must be addressed, and the electricity sector is an example of where cost effective technology and policy solutions exist currently.

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