Where does our energy come from? It is a good question to ask given that the country of India experienced its second day of wide-spread electric power interruptions that impacted 670 million people or 10% of the world’s population. According to the New York Times [Ref 1], three of the country’s interconnected northern power grids collapsed for several hours, as blackouts extended almost 2,000 miles, from India’s eastern border with Myanmar to its western border with Pakistan.
Over the past 12 months, as we witnessed rising then falling prices for crude oil and gasoline, many U.S. citizens have asked “where does our energy come from”. My blog posts and research on energy topics led me to ask myself the following question: What are the sources of energy in the United States? This question is the subject of today’s post.
To answer this question, it would be helpful to know if an inventory of energy sources is available. I consulted the U.S. Department of Energy (DOE) for an answer. Through its Energy Information Administration (EIA), DOE tracks one or more of the following metrics: reserves, production, consumption, imports, and exports for each energy source.
The U.S. has known reserves for petroleum (oil), natural gas, and coal – these are commonly referred to as fossil fuels. Add nuclear power and renewable sources to this mix and you have the primary energy sources for this country.
Crude Oil Proven Reserves (Unit of measurement: barrels [42 gallons] of oil)
EIA reports that our crude oil proven reserves on 12/31/2009 are 20,682 million barrels.
From one year to the next, EIA makes adjustments to their annual numbers. These adjustments include revision increases, revision decreases, sales, acquisitions, extensions, new field discoveries, new reservoir discoveries in old fields, and estimated productions.
Coal (Unit of measurement: short tons [1 short ton = 2,000 pounds])
Similarly, the U.S. tracks the amount of coal reserves each year. Figuring out how much coal we have is a bit of a challenge, and is based on estimates because much of the coal is buried underground.
- Coal Reserves at Producing Mines – this is the estimate of coal that can be recovered from active U.S. mines that annually produce at least 10,000 short tons. As of January 1, 2011, the recoverable reserves at producing mines were 17.9 billion short tons.
- Total Resources – this is the best estimate of the total amount of coal, discovered and undiscovered, in the U.S. The current estimate of total resources is 4 trillion or 4 x 1012short tons.
- Demonstrated Reserve Base – is the sum of coal in both measured and indicated resource categories of reliability, representing 100% of the in-place coal that could be mined commercially at a given time. EIA estimates the Demonstrated Reserve Base to be 484.5 billion short tons.
- Estimated Recoverable Reserves – include only the coal that can be mined with today’s mining technology, after accessibility constraints and recovery factors are considered. EIA estimates there are 259.5 billion short tons of U.S. recoverable coal reserves, about 54% of the Demonstrated Reserve Base.
Based on coal production for 2010, the U.S. recoverable coal reserves represent enough coal to last 239 years. This figure is often touted in one of the current energy/coal commercials on television.
However, EIA projects in the most recent Annual Energy Outlook (January 2012) that U.S. coal production will increase at about 0.4% per year for the period 2009-2035. If that growth rate continues into the future, U.S. recoverable coal reserves would be exhausted in about 168 years if no new reserves are added.
Natural Gas Reserves (Unit of measurement: cubic feet)
EIA reports that U.S. natural gas reserves on 12/31/2009 are 272,509 billion cubic feet.
In 2011, about 94% of the natural gas consumed in the U.S. was produced domestically. That is very good news for U.S. consumers because we are less dependent on foreign producers for this energy source than crude oil, and the delivery system is less subject to interruption. According to EIA, the availability of large quantities of shale gas should enable the United States to consume a predominantly domestic supply of gas for many years and produce more natural gas than it consumes.
Other Energy Sources
Renewable & Alternative Energy Sources: Unlike fossil fuels, which are exhaustible, renewable energy sources regenerate and can be sustained indefinitely. Also, unlike fossils fuels, there are no numbers to crunch for proven reserves.
The five renewable sources most often cited are: biomass (including wood and wood waste, municipal solid waste, landfill gas, biogas, ethanol, and biodiesel), hydropower, geothermal, wind, and solar. Renewable resources are primary used in the production of electricity.
Nuclear Energy: Atoms are tiny particles that make up every object in the universe. Nuclear energy is energy in the nucleus (core) of an atom. There is enormous energy in the bonds that hold the nucleus together. Breaking those bonds releases that energy. Nuclear energy can be used to make electricity, but first the energy must be released. It can be released from atoms in two ways: nuclear fusion and nuclear fission.
In nuclear fission, atoms are split apart to form smaller atoms, releasing energy. Nuclear power plants use this energy to produce electricity.
In nuclear fusion, energy is released when atoms are combined or fused together to form a larger atom. This is how the sun produces energy. Fusion is the subject of ongoing research, but it is not yet clear that it will ever be a commercially viable technology for electricity generation.
Most nuclear reactors are powered by uranium, a nonrenewable source. In 2011, we imported 91% of the 58 million pounds of uranium purchased by nuclear plants or operators.
Electricity as a Secondary Energy Source
In 2011, coal was the fuel of choice for about 42% of the 4 trillion kilowatt-hours of electricity generated in the United States.
Note: Unless otherwise indicated, the primary information source for the above information is the U.S. Energy Information Administration (EIA), www.eia.gov.
- New York Times, “2nd Day of Power Failures Cripples Wide Swath of India”, Jim Yardley and Gardner Harris, July 31, 2012 edition.