There are 3 different ways to look at quantities of available fossil energy
• Resources = The amount that may be present in a deposit or field. This
does not take into account the feasibility of mining economically. Not all
resources are recoverable using current technology but may become so
when technology improves.
• Probable reserves = The amount that is probably available and
• Proved reserves = Reserves that are not only considered to be
recoverable but can also be recovered economically and in an
environmentally acceptable way. This means they take into account what
current mining technology can achieve and what the economics of
recovery allow. Proved reserves will therefore change according to the
price of the energy type; if the price is low, proved reserves will decrease.
Estimates on coal reserves are quite accurate and reliable but there is
considerable uncertainty in the estimates of oil and gas reserves.
• Private oil companies have consistently underestimated their reserves
to comply with conservative stock exchange rules and through natural
• Whenever a discovery was made, only a portion of the geologist’s
estimate of recoverable resources was reported; subsequent revisions
would then increase the reserves from that same oil field over time.
• On the other hand, OPEC countries (that have the largest oil reserves)
strongly overstated their reserves while competing for production
quotas, which were allocated as a proportion of the reserves. They
never corrected their reportings.
• Russia’s gas reserves, the largest in the world, are considered to have
been overestimated by about 30%.
• There is also confusing terminology used- ‘proved’, ‘probable’,
‘possible’, ‘recoverable’, ‘reasonable certainty’ – and this adds to the
• Because of this unreliability, future energy safety precautions may be
Conventional fossil energy resources are coal, petroleum oil and
natural gas recoverable by traditional techniques at acceptable
economical cost. They amount to about 4000 TW, coal being 10
times more abundant than oil and gas.
Unconventional resources are resources that require novel
technology to become economically recoverable or cannot (yet) be
recovered for technical, economical or environmental reasons. They
occur trapped in geological formations, known as coal bed
methane, oil sands, shale oil, heavy and extra-heavy oil,
tight gas, shale gas and methane hydrates. Unconventional oil
and gas are present in much larger amounts than conventional oil
and gas, estimates ranging between 6000 and 25,000 TW).
Coal Oil Gas
Unconventional fossil energy
Not included in this diagram is traditional biomass energy (firewood,
charcoal, manure, crop residues), the natural energy source that humans have
used since the discovery of fire. It is still widely used in developing countries for
cooking and heating by poor rural populations. The annual consumption is ~1
Resources in terawatt (TW)
Estimates of conventional fossil energy reserves (coal, oil and gas) are about
4000 TW. At the present consumption rate (~18 TW), we can use this energy
for about 60 to 600 years, depending on the energy source (rounded). If
over time unconventional resources would become fully recoverable, we
would have for an additional 200-600 years.
However, predictions indicate that energy consumption will further increase up
to 2100, particularly in BRICS countries (Brazil, Russia, India, China, South-
Africa). These predictions seem to be accurate and may even be
underestimated since in 2001 the EIA predicted energy consumption for 2010
to be 16.4 TW and in reality it was 17.7 TW. Prediction for 2020 is 20.3 TW
and for 2035 25.7 TW. This evolution will lead to more rapid exhaustion
of fossil supplies, unless much more efforts will be done worldwide to
develop renewable energy facilities.
We cannot exhaust our fossil energy reserves as we depend on
petroleum and coal for basal ingredients of organic chemicals
Energy source Conventional
Coal 600 200
Oil 60 475
Gas 100 600
• Coal is formed from dead vegetation on land and algae in water after
being buried during the Earth’s geological history. Under suitable
conditions of pressure and temperature these plant residuals were
successively transformed into peat, lignite (brown coal), bituminous coal,
steam coal and anthracite. Coal is mainly carbon.
• Coal is primarily used as a solid fuel to produce electricity and heat
• If coal is blown through with oxygen and steam (water vapor) while also
being heated, the coal is oxidized to produce a gaseous mixture of CO2,
CO, H2O, and H2. The mixture is called syngas and can be used as an
energy source for production of heat and transportation purposes.
• Coal can also be converted by several different processes (coal
liquefaction) into synthetic fuels, equivalent to gasoline or diesel. This
approach is presently advanced to limit escalation of oil prices and mitigate
the effects of transportation energy shortage that will occur under what is
called ‘peak oil’ (see further).
Regional distribution of proved coal reserves
Oil as a fuel is a fraction obtained from petroleum distillation. Like coal
petroleum is formed from dead vegetation, usually zooplankton and
algae, after being buried underneath sedimentary rock under
intense heat and pressure during the Earth’s geological history.
Fuel oil is any liquid petroleum product that can be burned in a furnace
or boiler for the generation of heat or used in an engine for the
generation of locomotive power.
Petroleum consists of a complex mixture of hydrocarbons, most
commonly alkanes, cycloalkanes, aromatic hydrocarbons, or more
complicated chemicals like asphaltenes.
Regional distribution of proved oil reserves
• Natural gas is a naturally occurring hydrocarbon gas mixture consisting primarily of
methane, but commonly including varying amounts of CO2, nitrogen and hydrogen
• Natural gas is found in deep underground natural rock formations associated or not
with other hydrocarbon reservoirs in coal beds and oil deposits.
• Conventional gas is easily extractable by boring but needs to be transported to the
consumer. Over land this is through gas pipes. To transport it over sea or in case of
absence of pipe supply, gas is compressed to liquid, known as LNG (liquified natural
gas), and then transported to an LNG terminal where it is regasified and sent into
gas pipes. Recently, due to materials costs and lack of skilled labor and professional
engineers, designers and managers, the cost of building liquefaction and
regasification terminals has doubled. The LNG liquefaction business has been
regarded as a game of the rich, where only players with strong financial and political
resources could get involved. ExxonMobil, Royal Dutch Shell, BP, BG Group;
Chevron, are active players.
• Some hydrocarbon by-product of natural gas and crude oil have to be removed but
can be liquified for use as a fuel (Liquefied petroleum gas, LPG). It is a mixture of
propane, butane, and other hydrocarbons.
Natural gas is used for heating, household cooking, transportation and electricity
Distribution of proved gas reserves
This figure does not include the estimates of about 900 trillion m3 of
"unconventional" gas such as shale gas, of which 180 trillion may be
recoverable. (see later), potentially doubling the reserves.
has been proposed to run in
combination with a CO2
capture and storage (CCS)
procedure, which is, however,
seriously contested by
Underground coal gasification
eliminates surface damage and
solid waste discharge typical
for traditional coal power
plants, and reduces SO2 and
NOx emissions.It is also
less pollutant than
conventional coal gasification.
Some coal is technically or economically unrecoverable, i.e. is located too deep, is too low
grade, or seams are too thin. In that case it can be extracted by a procedure called
‘underground coal gasification’, UCG). Air and steam are injected in the seam, which
causes high pressure combustion (700–900 °C) converting coal to CO, CO2, hydrogen and
methane (called syngas) (C (in Coal) + O2 + H2O → H2 + CO and 2CO + O2 → 2 CO2). Gas is
then collected via a pipe. CO2 is unwanted as it is a greenhouse gas, but UCG
Underground coal gasification prospects
Coal potentially usable for underground gasification is widely distributed over the world.
Pilot projects are running in several countries.
Since conventional oil becomes less available and more expensive to extract today,
while demands increase, there is growing interest in production of fuels from
unconventional resources. In addition for certain countries it can improve energy
Unconventional oil types are: oil sands (tar sands, bitumen), heavy oil, extra-
heavy oil and shale oil.
Oil sands are formed from reservoirs of plant residues that escaped from deeper
storage and in this way get processed by biodegradation by microbes. The
material is very viscous, half-solid. Heavy and extra-heavy oil display lower
viscosity. Shale oil is present in rocks that have not been exposed to heat or
pressure long enough to convert their trapped hydrocarbons into crude oil.
Unconventional oil can be extracted by surface mining or by in situ extraction
Surface mining of oil sands in Alberta, Canada
Today energy equivalent to 1/8 tonne of oil is required to extract 3 barrels of conventional oil. In
surface mining of oil sands about 2 tonnes of oil sands are required to produce one barrel (roughly
1/8 of a tonne) of oil. This clearly demonstrates the much lower economical value of oil sands and its
much larger impact on land
In situ extraction of unconventional oil
Oil sands and heavy oil extraction Shale oil extraction
When heavy oil is fluid enough it is simply pumped out of the sands, although recovery is very low.
Cyclic steam stimulation is a method that pumps steam in the ground which makes the oil more
fluid and then the hot oil is pumped out of the well.
Oil from oil shale is extracted, either in a facility after mining or in-situ, by the chemical process of
pyrolysis: at 300–400 °C in the absence of oxygen, the oil is in part decomposed to yield a vapor of
hydrogen and methane while medium-weight hydrocarbons are converted into lighter ones. Upon
cooling the liquid oil is separated from the gas.
Shale oil resources
World Energy Council 2010
Heavy oil and oil shale resources by region
CIS= Commonwealth of Independent States
(previous Soviet states)
Tight gas is methane trapped in rocks with such
low permeability that it is impossible to extract
it with easy and cheep methods used for
conventional natural gas. Massive hydraulic
fracturing (‘fracting’) is necessary to extract it
from the rock (see figure). A large amount of
water is mixed with sand and/or chemicals and
injected at high pressure into faults to release
Shale gas is natural gas that is found trapped
within shale formations.[1 It also requires
massive hydraulic fracturing to extract.
Shale gas has become an increasingly important
source of natural gas. In 2000 it provided only
1% of U.S. natural gas production; by 2010 it
was over 20% and the EIA predicts that by
2035, it will be 46%.
Both shale and tight gas deposits may also be
located deeper than ordinary gas deposits,
giving additional problems for recovery
Tight gas and shale gas
Coalbed methane is a form of natural gas adsorbed into the solid matrix of the coal in
a near-liquid state. It is called 'sweet gas' because of its lack of hydrogen sulfide.
To extract the gas, a steel-encased hole is drilled into the coal seam (100–1500
meters below ground). The pressure within the coal seam is lowered by pumping
water from the coalbed, allowing desorbtion of the gas. Both gas and water come to
the surface through a pipe. Large amounts of water have to be disposed.
Environmentally acceptable disposal is a major cost factor.
Gas hydrates are crystalline water-based solids physically resembling ice, in which
small non-polar molecules (typically gases) or polar molecules with large hydrophobic
moieties are trapped inside "cages" of hydrogen bonded water molecules. When the
gas is methane it is called methane hydrate. Around 6.4 trillion tonnes is trapped in
deposits on the deep ocean floor. , in deep lake sediments (e.g. Lake Baikal),
the permafrost regions (such as in the Mackenzie Delta of northwestern Canadian
Arctic), as well as in arctic ice. Extraction is still in an experimental phase and has a
strongly negative ecological status.
Coalbed methane and methane hydrates
Health and environmental impacts of coal
Emission of CO2, a greenhouse gas, during combustion in power plants causes climate
change. Coal is the largest contributor to the human-made increase of CO2 in
Shortening of nearly 24,000 lives a year in the US, including 2,800 from lung
Annual health costs in Europe: 42.8 billion €.
Generation of hundreds of millions of tons of waste products, including mercury,
uranium, thorium, arsenic, and other heavy metals
Acid rain from high sulfur coal
Interference with groundwater and water table levels due to mining
Contamination of land and waterways, destruction of homes and background radiation
exposure from fly ash spills, (ash produced during combustion of coal) such as the
Kingston Fossil Plant coal fly ash slurry spill. A 2010 study in the U.S. by the
Environmental Integrity Project, the Sierra Club and Earth justice found that coal ash
dumped across 21 U.S. states has contaminated ground water with toxic material.
Impact of water use on flows of rivers and consequential impact on other land uses
Uncontrollable coal seam fire which may burn for decades and centuries
Coal gasification facilities deliver toxic products to the environment around the
Health and environmental impacts of oil
Along with the burning of coal, petroleum combustion is the largest
contributor to the increase in atmospheric CO2, causing climate change
and global warming
Crude oil and refined oil spills from tanker ship accidents have damaged natural
ecosystems in Alaska, the Gulf of Mexico, the Galapagos Islands, France and many
other places. Oil spills at sea are much more damaging than those on land, since
they can spread for hundreds of km and cover beaches, killing sea birds,
mammals, shellfish and other organisms.
Offshore exploration and extraction of oil disturbs the surrounding marine
Oil contaminants (pyridine, picoline, and quinoline) are very soluble in water,
and thus may move with water in aquifiers.
Health and environmental impacts of natural gas
Burning natural gas emits greenhouse gasses causing climate change.
It is, however, a less emitting fuel (see next slide). According to the IPCC,
natural gas produced about 5.3 gigatonnes a year of CO2 emissions in 2004, while
coal and oil produced 10.6 and 10.2 gigatonnes, respectively.
Natural gas emits particulate material but far less than coal (see next slide).
Natural gas produces far lower amounts of SO2 and nitrous oxides than any other
hydrocarbon fossil fuel
Gas also contains Radon, from 5 to 200,000 Becquerels per m3
Explosions caused by gas leaks at places of consumption or in gas pipes occur a
few times each year.
Some gas fields yield sour gas containing the toxic gas H2S.
Extraction of natural gas leads to decrease in pressure in the reservoir, which may
result in sinking of the ground above. This may affect ecosystems, waterways,
water supply systems, foundations, and so on.
Concerns over the safety of LNG terminals has created extensive controversy in
the regions where plans have been created to build such facilities.
Underground gasification is much less harmful to the environment and climate
than conventional coal combustion as the energy used is that of methane only.
Toxic materials (such as phenol) remain in the underground after underground
gasification and are likely to leach into ground water, although persistence in the
water appears to be short.
All types of mining can cause ground subsidence, but the depth of the void left
after underground coal gasification is typically more than other methods of coal
It remains to be seen whether underground coal gasification can increase the
incidence of coal fires. Thousands of coal fires are burning around the world.
Those burning underground can be difficult to locate and many cannot be
extinguished. Fires can cause the ground above to subside, their combustion gases
are dangerous to life, and breaking out to the surface can initiate surface wildfires.
Recovery of oil in open mines causes enormous environmental damage. In
northern Alberta, Canada oil sands are found beneath more than 54,000 square
miles of prime forest. Millions of tonnes of plant life and top soil are scooped away
in vast opencast mines. Millions of litres of water are diverted from rivers. Up to
five barrels of water are needed to produce a 1 barrel of crude oil and the process
requires huge amounts of natural gas. Two tonnes of oil sands produce only 1
barel of oil (140 kg).
Mining of unconventional oil requires significant new industrial
infrastructure: roads, power plants, power distribution systems, pipelines, water
storage and supply facilities .
Extracted unconventional oil contains contaminants such as sulfur and heavy
metals that are energy-intensive to extract and may have negative impact on the
environment such as leaving tailings – ponds containing hydrocarbon
sludge.[The toxic components in it can be fatal to birds that land on the surface
Energy requirements to extract oil, especially oil shale, are huge, resulting in
high production costs. Pyrolysis of oil shale requires extreme temperature (300-
400 °C). Oil shales contain high levels of inert mineral matter (60-90%), which is
higher than in coals. To extract this oil there is up to 4 times more greenhouse
gas emission per barrel compared to conventional oil extraction.
View over oil sand mines in Alberta (recognized as one of the largest reservoirs of
petroleum in the world), showing dust and the ponds containing hydrocarbon
Photograph by Peter Essick,
Shale and tight gas
• Extraction of shale gas emits larger amounts of greenhouse gas methane than
does conventional gas.
• Hydraulic fracturing fluid is water with approximately 0.5% chemical additives
(friction reducer, agents countering rust, agents killing microorganisms). Since
millions of liters of water are used, this means that hundreds of thousands liters of
chemicals are often injected into the soil. Only about 50-70% of the resulting
volume of contaminated water is recovered and stored in above-ground ponds to
await removal by tanker. The remaining water is left in the ground where it can lead
to contamination of groundwater aquifers.
• Fracturing may cause earth quakes. Beginning in 2001, the average number of
earthquakes in the US occurring per year of magnitude 3 or greater increased
significantly, culminating in a six-fold increase in 2011 over 20th century levels.
• The disposal of large amounts of possibly chemically contaminated water may be an
• Recovering the methane is difficult and if gas is unintentionally released to the
atmosphere during extraction, it may lead to a global climate change.
• Massive release can trigger landslides, earthquakes and tsunamis.
• Safe and economic extraction technologies are yet to be developed. Hydrates also
contain high levels of CO2 that have to be captured to produce quality gas.
In 2008, the European Environment Agency (EEA) documented the actual pollutant
emissions from power plants in the European Union. It is clear that of all fossil fuels
natural gas is the cleanest.
Pollutant (g/GJ) Hard coal
Fuel oil Other oil Natural gas
CO2 94,600 101,000 77,400 74,100 56,100
SO2 765 1,361 1,350 228 0.68
NOx 292 183 195 129 93.3
CO 89.1 89.1 15.7 15.7 14.5
Non methane organic
4.92 7.78 3.70 3.24 1.58
Particulate matter 1,203 3,254 16 1.91 0.1
Flue gas volume total
360 444 279 276 272
CO2 emissions doubled between 1973 and 2010, from 15 to 30 gigatons per year. In
June 2013 the International Energy Agency reported that global CO2 emissions hit a new record
in 2012: 31.6 gigatons, which is > 1 gigaton more than in 2010. The largest contributor was
China. Its emissions in 2012 rose 3.8 % compared to the previous year, although the increase
was smaller than before (due to renewable energy development). On the other hand, emissions
decreased by 3.8 % in the U.S., in part due to a switch in power generation from coal to gas.
Japan had higher emission due to a switch in power generation from nuclear to coal as a
consequence of the Fukushima disaster Read more
Emissions of greenhouse gasses by burning coal, oil and gas at present
rates are far above the Earth’s capacity to absorb the emitted carbon. It
provoked global warming, melting of sea and land ice, sea level rise,
extreme weather events and other climate changes. Greenhouse gas
absorption is a slow process while greenhouse gas emissions increase
continuously. It is believed that global warming will seriously affect human
civilization if it is not mitigated urgently and more than has been done up
The Intergovernemental Panel for Climate Change (IPCC) predicted that
global average temperature will rise with 4 °C by the end of the century.
Recently the International Energy Agency predicted a 5 °C rise.
1. Climate change
Increased annual demand for
oil and gas associated with a
decline in discoveries of new
reserves may lead to an
unprecedented energy crisis
In order to satisfy demands oil
is extracted or planned to
extract from locations posing
increasing costs and risks to
extraction (e.g. Brazil 's
offshore pre-salt basins, 5.5 km
deep under the ocean surface).
Consumption of non-
conventional sources is
more expensive and more
problematic for the
2. Energy crisis
This may lead or has already lead to what is called ‘peak oil’. It is the point in time
when the maximum rate of petroleum and gas extraction is reached, after which the
rate of production is expected to enter terminal decline ... 39
… and a fourfold increase in price over the last 12 years
Timing of peak oil and peak gas
Hubbert designed a method that predicts the peak of extraction of any resource.
Opinions as to the timing of peak oil are not unanimous but it is thought to be
soon. Peak oil was predicted to occur during the first decade of this century, but it
did not. The massive exploitation of unconventional oil in Canada and USA may
postpone ‘peak oil’, but it is believed that it will for sure occur in the near future.
Even though unconventional oil production technologies may further develop, it is
assumed that peak conventional ‘cheap’ oil has already been reached, and
therefore the era of relatively inexpensive oil production has ended.
‘Peak gas’? While the EIA predicts that world natural gas production will continue
to increase through 2030, others predict a global decline in conventional gas
production from about 2020. Decline may be attenuated by the discovery of
massive amounts of unconventional reserves, e.g. tight gas and shale gas.
Nevertheless, unless the latter reserves are further extracted, which has many
inconveniences, ‘peak gas’ will soon be a reality or is already present.
Consequences of peak oil and peak gas
Peak-oil and peak-gas will reduce the prospects for economic growth in both the
developing and developed world. Such an economic slowdown would exacerbate
other unresolved tensions, push fragile and failing states further down the path
toward collapse, and perhaps have serious economic impact on both China and India.
At worst it would lead to unprecedented dramatic conflicts.
‘Peak oil’ is particularly problematic for the U.S. The U.S. uses 25% of the
world's oil supply, but represents only 5% of the world's population. It uses 10 times
more oil per person per day than Europeans. The extremely high daily oil consumption
of the U.S. is due to the extremely inefficient nature of its transportation system –
based on individual vehicles, combined with a bad railroad network and
sprawling community designs that force people into cars for every trip.
Moreover, if alternatives of energy supplies are not or too slowly forthcoming, the
products produced with oil (including chemical reagents, pharmaceuticals, fertilizers,
detergents, solvents, adhesives, and most plastics) would become scarce and
expensive on top of international supply shortage. See also the Hirsch report
To avoid the serious social and economic implications of a global decline in oil
production, the 2005 Hirsch report emphasized the need to find alternatives, at least
ten to twenty years before the peak, and to phase out the use of petroleum
over that time. This was similar to a plan proposed for Sweden. At present we
don’t see much of a concern to meet these proposals! Indifference may drive
us into big trouble.
Consequences of peak oil for transportation
Peak oil will mostly affect the transportation sector since fossil oil is the fuel for >95% of
all transportation vehicles (see slide 10), and, since passenger cars and trucks represent
72 % of road vehicles (in the U.S. 82 %), it will have a large impact on all of us. In
contrast, very little oil is used for electricity generation (see slide 10),
Energy consumption by transport mode in the
EU-27 (European Environment Agency, 2012)
Energy consumption by transport mode in the
U.S. (Department of Energy, 2010). 43