Securing the Supplies of Fossil Fuels - Energy and Climate: How to Achieve a Successful Energy Transition - page 97

per barrel, are economically acceptable. Still, these processes require a
great amount of energy, generate very significant emissions of CO 2 and
require large quantities of steam and therefore of fresh water. To exploit
extra-heavy oils in an acceptable way, it will be necessary to develop
technologies which minimise the impact upon the environment and
especially CO 2 emissions.
Canada and Venezuela presently produce 1.8 million barrels a day, i.e.
2%of theworld oil production. InCanada alone, the production of heavy
oils from tar sands exploited by surface mining could reach 1 million
barrels a day by 2010 and 5 million barrels a day by 2030.
In terms of resources, extra-heavy oils represent a huge potential,
around 1200Gb each for Venezuela and for Canada. It is estimated that
around a quarter of these resources, i.e. 600Gb, can be exploited by using
already known technologies [80].
An oil shale is formed by a fine-grained sedimentary rock containing an
organic matter which has not been completely converted into oil. Shale oil
can be exploited by using mining technologies, but its exploitation has a
strong environmental impact: in the case of surface mining, destruction of
vast natural areas, increased erosion, large energy consumption for
processing the shale and extracting the oil, acid drainage, and air pollu-
tion. To date, its exploitation has not appeared to be economically
competitive, as compared for instance with coal mining.
Natural gas
The development of natural gas has been quite rapid in recent years. It has
become a widely used and excellent fuel for power plants, presenting
strong environmental advantages (providing a clean fuel emitting 50%
less CO 2 per unit energy output than coal and 30% less than fuel oil)
which can be used in an efficient and flexible way. Natural gas fired power
plants require comparatively low investments and are quick to install.
Combined cycle power plants, which associate a gas turbine with a steam
cycle exploiting heat recovered from the gas turbine exhaust gases, reach a
high efficiency, close to 60%. Gas fired power plants emit few pollutants
to the atmosphere. Compact, quick to build and requiring a comparatively
small investment, they have developed rapidly.
Natural gas is used also for residential heating applications and as a fuel
in industry. Stored under pressure in a tank, it can even be used as an
engine fuel, called NGV (natural gas for vehicles). This option can be
applied for diversifying engine fuel supply sources. If it is properly used in