Should we use net energy to measure global energy reserves?
Posted on Monday, April 10, 2006 @ 20:55:50 UTC by vlad
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by Kurt Cobb
Net energy is a simple concept really. Once you understand that it
takes energy to get energy, the basic math is clear. To calculate the
net energy available from an energy resource, you add up the energy
used to find, extract, process and deliver that resource and then
subtract that amount from the amount of energy the resource contains.
But global reserves for finite energy resources such as coal, oil,
natural gas and uranium are estimated using measures such as tons,
barrels, cubic feet and pounds. These measures tell us little about the
ultimate usable energy content of each type of resource.
Nor is it of much use to compare the relative gross energy values of
these resources, though such comparisons are readily available. To see
some examples, check out this one showing the oil equivalence of nuclear fuel, this one for oil and natural gas, and this table containing a variety of equivalences including two comparing coal and oil. Even conversions into British Thermal Units, or BTUs, don't really help us.
As
the world moves ever closer to the time when vital, finite energy
resources begin to decline, we need to know not how much oil, natural
gas, coal or uranium is left; rather, we need to know how much usable energy
is left in these resources. A recent illustration of the problem we
face in understanding usable energy supplies came in the form of a 60 Minutes story on the Canadian oil sands.
The program reported that "the reserves are so vast in the province of
Alberta that they will help solve America’s energy needs for the next
century."
Nowhere does the reporter explain how much energy it
takes to mine and refine the bitumen--it's not actually oil. In fact,
it takes two barrels of oil equivalent to obtain three barrels of usable oil from the oil sands.
(This is a far lower return than we get from conventional oil which can
provide 20 times the energy consumed for older oil discoveries and
eight times the energy consumed for newer oil discoveries.) By this
standard we should reduce the generally accepted 180 billion barrels of
reserves in the Canadian oil sands by 40 percent. Now, not all of the
energy used to mine and process the oil sands comes from petroleum. Of
course, the huge mining trucks and other equipment run on diesel fuel.
But, the processing plants are heavy users of natural gas, both to heat
water for the separation process and to provide a source of hydrogen to
transform the bitumen into a flowing, light oil.
But, this shows
why we need to know about the total universe of finite fuels since each
one increasingly interacts with the others during processing, and one
fuel may be called upon to substitute for the another as each resource
peaks and then declines in availability. Some say that peak oil
production is already upon us. The rate of production for conventional
natural gas, which many experts tout as a substitute for declining oil
supplies, may peak by mid-century. And, while there are claims that the
world has enough coal for 300 years, it is important to note that such
figures are always followed by the phrase "at current rates of consumption."
Naturally, if we had to rely more and more on coal, not only for
electricity, but also for heat and liquid fuels, its rate of
consumption would rise dramatically. Even more worrisome, the net
energy of coal is declining. Richard Heinberg reports in his book The Party's Over
that on the current trajectory the net energy from coal could go
negative by mid-century as coal grades continue to decline. As for
uranium, information on its future supply is sketchy at best.
Oil
is facing its own foreshortened depletion trajectory with peak
production predictions ranging from last year all the way to 2037 (a
date which seems far too optimistic). Increasingly large amounts of
energy are needed to find new oil. This is only logical since 1) the
easiest oil to find, extract and process has been used first, 2) the
new finds tend to be in more remote places such as the Arctic and 3)
the new finds tend to be in smaller reservoirs. In addition, new oil is
also often more energy intensive to refine because it tends to be of a
lower quality. The oil sands are a prime example.
To get the
total picture of our finite energy reserves, we need to know at least
four important things beyond the raw amounts left: 1) the net energy
available from each resource given today's technology and given
projected improvements in that technology over time, 2) the rate at
which each resource is likely to be extracted over time, again
adjusting for improvements in technology--even a very dense energy
resource is of little use if it can only be extracted at a trickle--3)
the current and projected interchangibility of finite fuels and their
renewable replacements and 4) the time it would take to move toward a
new energy infrastructure to accommodate such substitutions. For
instance, if coal liquids are going to be substituted for declining
supplies of refined oil products, the equation for our energy resources
will change dramatically. And, the time it would take to ramp up such
production will be an important consideration in its feasibility. (This
example does not attempt to address the implications for global warming
which need somehow to be considered.)
Modeling these four new
pieces of information together with estimates of raw reserves may seem
daunting. But, it is actually considerably less daunting than the
problems already tackled by those who sought to model future economic
constraints in Limits to Growth, the excellent study of resource and pollution constraints on industrial expansion.
Given the gravity of the energy challenges we face, can we afford not to try?
Source: http://www.energybulletin.net/14746.html
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