the story behind
Natural gas is a major component of energy supply in the United States, representing 23% of all fuel consumed. In some states like California, it is the primary fossil fuel burned to heat homes or to generate electricity.
Why is this? For one, it is clean burning, meaning that “pound for pound” it doesn't result in as much carbon dioxide or air pollutants as do fuel oil or coal. And, it is relatively plentiful: over 95% of the natural gas we burn in the US comes from North America, as compared to only 33% for oil1.
But, is this the entire story? Is there a downside to using more natural gas in the future? To explore further, read on.
where it comes from
Like other fossil fuels, natural gas comes from the decomposition of ancient marine life, buried deep beneath the ground over millions of years where it was heated under great pressure. It is not one “gas” per se, but instead a mixture of several gases consisting primarily of methane.
It is often found in the same areas as is oil, but is also sometimes found in fields where it is the primary product. Historically, it was often seen as a waste product of oil exploration: because it is a gas, it was much more difficult to transport. This often led to natural gas being burned off as oil was brought to the surface. Now, pipelines are built to carry it across continents, and increasingly it is compressed and liquefied, put into giant tankers, and moved across oceans in much the same way as oil.
In the United States, natural gas now makes up 23% of overall energy consumption, and US Government projections suggest this will not change in the foreseeable future. However, because of rising energy consumption in the US, natural gas use is projected to increase by 17% over the next ten years.
Today, over 97% percent of our natural gas comes from North America (including Canada and Mexico), while 84% comes from the US itself (see chart to left).
However, even though the situation is attractive today, the US only holds 3% of the world’s proven reserves. As worldwide consumption grows, natural gas will increasingly come from overseas. Government projections show that by 2015, 20% of natural gas used in the US will come from overseas2. Shipments from Canada via pipeline are projected to remain relatively constant; therefore, the balance will most likely come via liquefied natural gas (LNG) tankers from countries in the Persian Gulf and Russia (see figure to the left). At that point, we may be in the same situation as we are with oil today – dependent on foreign suppliers in unstable parts of the world.
1 2005 estimate from http://tonto.eia.doe.gov/dnav/pet/pet_sum_crdsnd_adc_mbbl_a.htm
2 Calculated from EIA data, assuming net imports of 5.1TCF (3.1 LNG, 2.2 Canada, -0.14 to Mexico) and total consumption of 26 TCF in 2015
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