michaelminn.net / Energy / Nonrenewables

Availability of Future Non-Renewable Energy Supplies

Annual consumption and years left figures are based on overall consumption for that particular class of fuels (e.g. liquid fuels, gas) rather than the current rates of production of that particular type of fuel. The intention is to place the reserves in a broader context and demonstrate that nationalist hopes for American non-renewable energy independence for any extended period of time face may be unrealistic.

Conventional Petroleum

Around 70% of American petroleum consumption was for transportation (EIA, 2012, 117), and American transportation is almost totally dependent on petroleum, which accounts for around 94% of direct transport energy use (Davis, Diegel and Boundy, 2009, 1-1, 2-4).

The amount of remaining petroleum is a subject of considerable debate and is highly uncertain. Although petroleum availability is best expressed as reserves, which is the estimated amount that can be profitably extracted from known discoveries using existing technology, media reports frequently cite resource numbers, which represent the estimate of the total amount of the resource in the ground and which are likely much higher than the amount of the resource that will ultimately be produced. A 1996 USGS study indicated that undiscovered resources might represent up to 3,000 billion barrels.

Petroleum reserve estimation is an inexact science that is complicated by powerful political and commercial forces. The foreign reserve estimates from the EIA (2009a) are accompanied by the caveat that such figures are, "very difficult to develop," and that they simply made foreign fuel estimates available but did not certify the figures. The EIA figures come from three commercial sources: the oil company BP, Oil & Gas Journal and World Oil.

OPEC figures are especially suspect, especially since 1985 when the cartel decided to link production quotas to reserves estimates, resulting in suspicious increases in reserves declarations (Rodrigue, Comtois and Slack, 2009; Ying, 2007). A Wikileaked 2007 cable from an Aramco engineer and board member indicated that Saudi estimates of total reserves of 900 billion barrels might be overstated by as much as 300 billion barrels and that production from aging fields would begin declining after only 64 billion barrels.

Tar Sands / Natural Bitumen

Tar sands are deposits of bitumen - complex hydrocarbon molecules that comprise a very thick form of petroleum mixed with sand and water. Alberta and Venezuela contain vast deposits of bitumen close to the surface. Extraction of the bitumen and synthesis into liquid fuel requires significant amounts of water and input energy (usually from natural gas), resulting both in severe environmental degradation and low EROI. Nevertheless, as petroleum has become less plentiful and more expensive, oil sands have become increasingly viable economically and will likely be a significant world source for energy for many years (Rubin 2009, 42-45; Smil, 2010, 69-72).

While some Americans look to the Canadian oil sands as a potential path to freedom from foreign energy dependency, fuels are traded on a global market and there is no assurance that all or even most of the oil extracted from the Canadian tar sands will end up powering American SUV's. The EIA (2011d) notes that Chinese firms are, " beginning to forge a potent presence in the oil sands." As Chinese and Indian economic development continues and automobility expands, many generations of Canadians will likely pay a heavy environmental price for only a few decades of continued world automobility.

Oil Shale

Oil shale is a precursor rock to petroleum that has never been deep or confined enough to form oil deposits. One of the world's largest oil shale deposits is the Green River formation that spans Colorado, Wyoming and Utah. Although oil shale exists in many countries around the world and has been commercially exploited, low petroleum prices have thus far made it economically unattractive except in a handful of locations (Deffeys, 2005, 109-123).

Extraction of oil from the rock requires water and some variation on heating, which converts the organic kerogen to usable oil. As with tar sands, this results in high environmental impact and low EROI. But given the vastness of this resource, oil shale may have a significant role in the closing decades of the fossil fuel era if some way of economically tapping the resource can be found.

The 60% net recovery factor is from Bartis et al (2005).

Note that oil shale should not be confused with shale oil (or tight oil) which is conventional petroleum locked in dense rock formations that can be extracted using hydraulic fracturing.

Coal

Coal is the granddaddy of industrial-age fossil fuels and still has quite a bit of life left in it. In 2007, coal was the source for 27% of world energy consumption, with 64% of that used for electrical power generation. While coal consumption has been flat in developed countries for a number of decades, it's use in developing countries has spiked since 2000 and is expected to continue to grow significantly (EIA 2010c). Liquid fuels derived synthesized from coal using the Fischer-Tropsch process powered the German war machine in World War II and changing energy economics are reviving interest coal-to-liquid fuels as a drop-in substitute for dwindling petroleum supplies from often insecure sources (Kreutz et al, 2008).

A challenge with assessing coal reserves and consumption is that quality and heat content of coal varies widely depending on the resource. The gold standard is Anthracite that can contain up to 98% carbon and have a heat content of 28 MM BTU/ton. At the other end of the spectrum is lignite, which can contain as little as 25% carbon and have a heat content of 9 MM BTU/ton. BP (2015) reports reserves in high and low groups: Anthracite/Bituminous and Sub-bituminous/lignite. In the calculations above Anthracite/Bituminous is converted at 24 BTU/ton and Sub-bituminous/lignite at 15 BTU/ton.

Further, the EIA groups reserves as recoverable at producing mines, estimated recoverable reserves, and demonstrated reserve base. Estimated is demonstrated minus considerations for land use restrictions and assumed recovery rates. Economic feasibility is not considered, so although the US clearly has a vast resource, the amount that can be extracted at a profit in the face of environmental concerns is an open question.

Although coal extraction is perilous to both miners and the environment, and the fuel has a high carbon content that makes a significant contribution to climate change, it's abundance, economy, ease of use and high EROI will likely make it a significant component of the world energy market for decades to come. And there may be a historical symmetry as the first fossil fuel becomes the last fossil fuel as oil and natural gas reach their inevitable depletion.

Natural Gas

Natural gas is primarily methane (CH₄) with varying mixtures of more complex hydrocarbons. Although gas for fuel can be produced from other sources (notably coal or decaying municipal waste), since the mid 20th century most natural gas has come from wells. Conventional natural gas deposits are either dissolved in oil deposits, sit in a cap above oil or coal deposits, or come from depths below 15,000 feet where heat and pressure break hydrocarbons down to the simple single-carbon molecule (Deffeys 2005, 52-81).

More recently, higher prices and technological innovation (notably, hydraulic fracturing) have made extraction of gas trapped in sedimentary shale deposits both practical and lucrative. This development has opened vast new fossil fuel resources which Smil (2010, 56) argues will significantly prolong the fossil fuel era as a substitution for declining petroleum availability. However, the price of that prolongation may significant contamination and overuse of surface and subterranean water supplies (MITEI 2010, 14-16; Osborn et al 2011) along with exacerbation of anthropogenic climate change.

Given the relative novelty of shale gas extraction and the size of the potential resource, the amount of gas ultimately recoverable at a profit is uncertain.

Although shale gas extraction would seem to be more energy intensive than conventional natural gas extraction due to the physical fracturing needed to free the gas from the rock, Yaratani and Matsushima (2014) actually give a mean EROI of 12, which is slightly better than the overall natural gas numbers provided by Murphy and Hall (2010). A non-peer-reviewed report posted on the peak oil site The Oil Drum (Friese, 2008) anticipated a fairly rapid EROI decline to break-even.

Methane Hydrates / Methane Clathrates

Methane hydrates are molecules of methane locked in water crystals - effectively natural gas in ice. These compounds are formed where methane and water are present at low temperatures and high pressure, such as the ocean sediments. There are orders of magnitude of uncertainty about the global resource, and since there has been no commercial hydrate production, reserves are only wild guesses. But there is unquestionably enormous potential - leading to the oft-stated dream of a 1,000 year supply (NGSA, 2012).

There are numerous ongoing research projects into methane hydrate gas production (USDOE, 2012) and the NRC (2012, 6) observed no insurmountable technical challenges to economically-viable commercial development. But for now, exploitation of this resource remains hypothetical, with ultimate production, as usual, likely to be considerably lower than whatever the global resource actually is. And the climate implications of releasing all that carbon into the atmosphere are (ironically) chilling.

Uranium

Although Lewis Strauss's promise of electricity that was, "Too cheap to meter" never came true (Smil, 2010, 31), electricity generated with nuclear fission still accounts for 14% of world electricity generation (EIA 2010c). Nuclear power provides 75% of France's electricity (WNA, 2011) and 49% of the electricity in Illinois (NEI, 2010). While growth in the United States has been stalled by massive costs, waste disposal issues and a hostile public, nuclear fission remains a vital part of the debate over the future of energy. Both Deffeys (2005, 124-151) and Smil (2010, 31-43) find a rare point of agreement that nuclear belongs in the world's energy future.

In addition to the geologic uncertainties about exact quantities of extractable uranium, the actual amount of fission energy available will likely be increased by improved reactor and fuel processing technology in the future. And the development of commercially-viable fusion would be a game changer for the planet. But it remains to be seen whether the need for cheap electricity ultimately overwhelms all the negatives associated with nuclear power.

Fuel to BTU conversions are based on BTU calculated backwards from electrical output using a thermal conversion rate divided by the US share (33%) of nuclear fuel use (WNA 2014b-c). The calculated figure of 35,400 kWh/kg is an order of magnitude below below the WNA (2015a) figure of 360,000 kWh/kg. And this is substantially lower than the theoretical amount of heat available with complete consumption of all fissile material in the fuel.