For over a hundred years, the United States energy sector has been dominated by three fossil fuels: oil, natural gas and coal. Today, the revolution is renewable.
The main changes in the history of energy in the United States came about through the development of new resources. After the use of wood, in the early nineteenth century, and of watermills that powered the first years of industrial growth, at the end of the nineteenth century coal became the first primary energy source. In the mid-twentieth century oil and natural gas took on a fundamental role and a new form of energy emerged: nuclear. Until the end of the twentieth century, the energy sources most widely used, taken together, remained the same. The current growth in domestic production of petroleum liquids and natural gas has pushed coal into second place in electricity generation. Overall, oil, natural gas and coal have provided more than 80 per cent of primary energy over the past decade.
The 2014 annual coal report, produced by the US Energy Information Administration (Eia), shows that coal production grew by 1.5 per cent compared to the previous year, but the number of people employed in the coal industry fell for three consecutive years, settling at 74,931 workers. Coal covered 18 per cent of energy consumption in 2014, a slight decrease (0.7 per cent) compared to the previous year.
The United States is a net exporter of coal and the industry's turnover in 2014 was approximately 46 billion dollars. But even though domestic demand for the fossil fuel stood at around 917 million tonnes and the country had produced 997 million, the government chose to import it because it was cheaper.
The coal industry, however, is in crisis due to the growth of cleaner and cheaper energy sources such as natural gas, solar and wind. Sixty-five per cent of the coal produced in the country comes from surface mines, which have a very negative impact on the surrounding environment. For example, mountaintop removal and valley filling has affected vast areas of the Appalachian Mountains in the states of West Virginia and Kentucky. Mountain summits are levelled using explosives, and the runoff water from the valleys often contains pollutants.
Between 1900 and 2006, as many as 11,606 miners died in 513 disasters caused by underground coal mining. The deaths resulting from three accidents that occurred during 2006 were among the reasons that led to the drafting of the Miner act (Mine improvement and new emergency response act), aimed at improving safety, health, action and emergency response.
The United States is the world's largest oil-consuming country: in 2014 consumption reached up to 19 million barrels of petroleum products per day, equivalent to approximately 20 per cent of global consumption. Oil covers approximately 35 per cent of domestic energy demand and is used primarily in the transport sector (71 per cent) and industry (22 per cent).
The country is also the world's third-largest crude oil producer and a major exporter of petroleum liquids and refined products, even though only 1 per cent of the electricity generated in the country comes from oil. Crude oil production grew following the general decline that occurred between 1985 and 2008, thanks to the use — particularly in the states of Texas, North Dakota, Oklahoma and Colorado — of economically more advantageous drilling technologies.
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Net imports (i.e. imports minus exports) of crude oil and petroleum products in 2014 averaged 5.2 million barrels of petroleum products per day and accounted for 27 per cent of total US oil consumption, the lowest level recorded since 1985.
The main factor that has allowed the United States to increase domestic oil production and rely less on imports from Middle Eastern countries has been the growth of hydraulic fracturing, or fracking. This practice requires large quantities of water and the use of potentially harmful chemical substances that allow oil to be extracted from deeper rock layers. The construction or poor management of faulty wells can cause fracturing fluids to leak. Hydraulic fracturing also produces large quantities of wastewater that may contain contaminants. The waste water is usually injected into deep wells, a practice that could even trigger seismic tremors, although studies are not yet in agreement on this point.
In 2014, natural gas met 28 per cent of US primary energy demand. The country consumes more natural gas than it produces: although most natural gas is produced domestically, this resource is imported in large quantities. Dependence on imports has decreased in recent years thanks to the growth of domestic production, driven by the use of more efficient and profitable production and drilling techniques, particularly in shale, sandstone and carbonate geological formations. Net imports of natural gas accounted for 4 per cent of the natural gas consumed in 2014, compared to a peak of 16 per cent in 2001, 2005 and 2007.
Natural gas produces fewer fine particles than coal and refined petroleum products. This has contributed to its increased use in electricity generation and in the transport sector. However, natural gas is made up mostly of methane, a potent greenhouse gas. The gas that partially disperses into the atmosphere is responsible for 29 per cent of total US methane emissions, but accounts for only 2 per cent of the greenhouse gas emissions recorded in 2013. Unprocessed natural gas can contain compounds such as hydrogen sulphide, a highly toxic gas, and is often flared, a process that produces compounds such as CO2 and carbon monoxide.
Furthermore, clearing large stretches of land is necessary for the construction of natural gas reserves and pipelines used to transport the resource. Drilling activities produce air pollution, and natural gas extraction can contaminate groundwater.
Nuclear energy meets around 8 per cent of American primary energy demand and is used solely to generate electricity. There are currently 99 nuclear reactors operating at 61 nuclear power plants across the United States. Since 1990, electricity generated annually through nuclear power has averaged 20 per cent. The Eia expects growth in domestic nuclear energy production, but at a rate of around one quarter relative to total electricity production. In 2014, revenues from nuclear power plants amounted to 40–50 billion dollars and more than 100,000 people were employed in the sector.
Nuclear reactors are fuelled by fissile material, in most cases uranium. Since 2009, this has been imported primarily from Canada and Australia, but above all from Kazakhstan. Nuclear reactors produce no air pollution or carbon dioxide while in operation and are highly efficient. However, they do produce radioactive waste that can remain so and pose a danger to human health for hundreds, if not thousands, of years.
In 2014, renewable energy consumption in the United States accounted for around 10 per cent of total energy consumption. 13 per cent of electricity in 2014 was generated from renewable energy sources. The most widely used renewable source is wind energy, which alone generates 5 per cent of electricity. Biomass comes second with 2 per cent of electricity generated in 2015 and is used to produce heat and steam for industry or for heating. Biomass, including biofuels such as ethanol and biodiesel, is used in the transport sector and is strongly promoted by state and federal government incentives. Its use is estimated to be growing in the coming years.
Biodiesel and ethanol are non-toxic and biodegradable substances and can be considered zero-emission because the plants from which they are made (soya beans and oil palms for the former, and maize and sugar cane for the latter) absorb CO2, offsetting the emissions generated by their production and use. On the other hand, large green areas and forests are being razed to the ground to make way for soya and oil palm plantations used in biodiesel production, and large amounts of land, fertilisers and energy are used in ethanol production, which contains toxic and highly flammable denaturants. The United States is a net importer of biodiesel and a net exporter of ethanol.
According to the new Advanced Energy Economy Report, advanced energy products and services aimed at improving energy efficiency are worth 200 billion dollars a year. Solar and wind, alongside natural gas, drove a 14 per cent increase compared to 2013, five times the growth rate of the United States economy.
The cost of producing renewables continues to fall over time, also thanks to regular funding and incentives, and in 2011 renewables overtook nuclear power in the United States in terms of energy production. The Eia's Energy Outlook 2015 shows the possibility of eliminating net energy imports between 2020 and 2030 and reflects, among other things, the growing use of renewables.
The United States emits 15 per cent of the world's carbon emissions. At Cop 21, the country committed to reducing its emissions by 26–28 per cent by 2025 compared to 2005 levels. The transition plan envisages:
At present, the best weapon against climate change is to rely on renewables. Their costs have fallen and there are ever newer methods for integrating them so that they become a primary form of energy. This means that greater quantities of energy will be used within the United States instead of being imported, and that CO2 emissions will decrease.
Translated by Francesca Clemente