RESOURCESSo far we have made projections about the amount of energy we can use before excessive global heating prohibits increases in consumption.

We then made projections about the amount of energy we are likely to use when world population reaches a steady state.

We saw this was a large increase in energy use and we questioned whether we have the resources to fulfil our requirements.

To answer this we need to examine how we use the energy available to us at the moment.

Energy use is split into 3 approximately equally sized sectors, these are:

HOUSEHOLD AND COMMERCIAL, INDUSTRIAL, TRANSPORT.

The main energy source remains overwhelmingly the burning of fossil fuel. Nuclear and hydroelectric contribute only small amounts. There continues to be a rapid increase in the contribution from renewables.

The energy is distributed largely as fuel burnt at the point of use.

Only about 10 % is distributed as electrical power (although this represents 34% of the total input to the system because of the relative inefficiency of electrical power generation.

OIL RESOURCESHistorically oil companies have mounted an exploratory effort sufficient to maintain reserves equivalent to between 10 and 20 years’ current production.

i.e. reserves have increased as production has grown.

We need to measure the resource limit. This is an analysis by Campbell and Laherrere in the March 1998 edition of Scientific American.

Three numbers are required to project future oil production:

- A total of how much oil has been extracted to date.

- An estimate of the reserves (the amount oil companies can pump out of existing fields).

- A guess at the quantity of conventional oil remaining to be discovered and exploited.

Together they add up to the finite quantity of the resource, rlim.

Cumulative production can be estimated reasonably well because oil companies monitor the oil flowing from their wells. Although this record is not perfect, it is sufficiently good that adequate estimates can be made.

OIL RESOURCES 2It is much harder, however, to find estimates of total current reserves.

These figures come from unchecked data received by trade journals from oil companies and governments. The figures are problematic for several reasons:

- estimating the size of a field is not exact and a range of reserve estimates with associated probabilities are usually supplied by a geologist to the producer.

- In practise the companies are often vague about the confidence of their reserve estimates and may publicise whichever figure best suits them, usually to enhance their market value.

- In the case of OPEC countries, the larger their reserve the greater the amount they can export. A big temptation to to produce optimistic estimates of reserves.

- An example of this is the suspicious leap in reserves by 6 of the 11 OPEC countries in the late 1980s. This followed take over of fields by governments from private companies. In part, increased estimates were warranted to update previous conservative extrapolations. However, there were no new fields discovered and no other major technological breakthroughs and yet the estimates increased by between 42 and 197%.

OIL RESOURCES 3Unproved reserves:

In the US, regulation allows companies to call their reserves “proved” only when the field is close to a current oil producing well and there is a “reasonable certainty” that oil is recoverable using existing technologies at current prices.

To estimate the unproven reserves Campbell and Lahererre used the median estimate of provable reserves in each field(the number of barrels of oil that are as likely as not to come out of any well.

According to their analysis there are 850 Gbo of conventional oil remaining in current wells. This estimate is lower than the 1019 Gbo reported in the trade journal.

This value equates to around 5 Q.

However, we also need to know the size of the ultimate recovery.

Currently, about 80 % of oil flows from fields found before 1973 and most are in decline.

C+L used the following techniques to estimate the total recoverable resource and arrived at a figure of about 1000 Gbo.

This gives a total remaining energy resource of 6 Q.

OIL RESOURCES 4The amount of remaining oil can be predicted from the decline of ageing fields.

The Thistle Field off the coast of the UK will yield approximately 420 million barrels.

40

30

20

10

0Ann

ual O

il Pr

oduc

tion

(Mill

ions

of B

arre

ls)

5004003002001000Oil Produced to date (Millions of Barrels)

OIL RESOURCES 5Cumulative discovered oil versus the cumulative number of exploratory wells in two regions: the former Soviet Union and Africa. Larger fields are found first so the curve rises quickly and then flattens to a theoretical maximum. For Africa this is 192 Gbo. But practically time and cost limits this to 165 Gbo.

300

250

200

150

100

50

0Cum

ulat

ive

Oil

Dis

cove

red

(Gbo

)

20x103151050Cumulative number of exploratory wells

AFRICA

SOVIET UNION

Theoretical Maximum

Practical Limit

OIL RESOURCES 6The distribution of oil field sizes in the Gulf of Mexico. The fields are ranked according to size and plotted on a logarithmic scale. The parabolas grow predictably over time.

0.1

1

10

100

Oil

Initi

ally

in F

ield

(mill

ions

of b

arre

ls)

100 101 102 103 104

Rank order of field (largest first)

1959

1969

1979

1993

Projected

OIL RESOURCES 7Estimates are checked by matching production to the rise and fall of discovery in those areas. In this case the world outside the Persian Gulf.

40

30

20

10

0Oil

foun

d or

pro

duce

d ou

tsid

e M

iddl

e Ea

st

202020001980196019401920Discovery Year

204020202000198019601940

Production Year

RESERVE AND RESOURCE OF A FOSSIL FUEL

CUMULATIVE RESERVE (r): The reserve of a commodity such as oil is the amount known to exist in specified places in the ground and extractable at a specific cost.It is reduced by extraction and use, but can be increased by exploration or by incorporation of higher cost deposits (given advances in extraction technology).It is therefore a function time r(t).

RESOURCE (R): The resource is the total extractable material deposited beneath the earth’s surface. The size of the deposit depends on how much you are prepared to pay and so is primarily a function of cost R(£).

MALTHUS’ EQUATION

The initial stages of growth of the cumulative reserve of a commodity such as a fuel can be described by Malthus’ equation as there is no limit on the amount of reserve available if necessary

The reserve held is entirely dictated by the demand up to present time, the rate of growth of the reserve is proportional to the magnitude of the cumulative reserve held.

crdtdr

=

THE VERHULST EQUATION

Later in the supply of the fuel it becomes apparent that the resource has a limit, the ultimate resource of the fuel, R. The rate of change of the cumulative reserve is therefore also proportional to the remaining undiscovered reserve. The less available the resource, the lower the rate of change of cumulative reserve. (R-r).

This can be solved algebraically:

If then and

and using

r)-cr(Rdtdr

=

−=

Rr

Rrc

dtRrd

R11

f rR

= ( )fcRfdtdf

−= 1 cRdtff

df=

− )1(

∫∫ =−

t

t

f

f

cRdtff

df

00)1(

dff f

dff

dff( )1 1−

= +−

THE VERHULST EQUATION 2

Integrating: gives:

Rearranging then

giving

Resubstituting for r and R gives

∫∫∫ =−

+t

t

f

f

f

f

cRdtf

dffdf

0001

)()(1)(1ln

)()(ln 0

00

ttcRtftf

tftf

−=

−−

−

)(0

0

0

)(1)(1

)()( ttcRe

tftf

tftf −=

−− )(

0

0 0

)(1)(

)(1)( ttcRe

tftf

tftf −

−=

−

)(

0

01)(

1)(

)(1 ttcRetftf

tf −−

−=

−( ) )(

00

0

0)(1)()(

)( ttcRetftftf

tf−−−+

=

)(00

0

01

)(ttcReR

rR

rR

r

Rtr

−−

−+

=

THE VERHULST EQUATION 3

The lifecycle of a fossil fuel

0

2

4

6

8

10

12

1960 1980 2000 2020 2040 2060 2080 2100 21200

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

cumulative reservecumulative productionreserveproduction

OIL RESOURCES 8Using an analysis based on the Verhulst equation C+L estimate that

1. North Sea fields will peak in production by the turn of the century

2. By 2002 the world will rely on the Middle east nations.

3. Once 900 Gbo (5 Q) has been consumed production will fall.

4. It seems likely that production of conventional oil will peak around 2010.

A separate estimate based on USGS 1991 figures, finds a total recoverable amount of remaining oil of 1550 Gbo, 55% higher, however, the peak is again predicted within the next 15 years.

A third estimate, made in 1997, shows twice as much remaining oil and a peak in production in 2020. The author concedes that his resource estimate is optimistic.

These estimates are essentially the same as those made in 1971 (8-12 Q remaining) and 1990 (7 Q left + 3 Q used from 1971) and now (5 Q and 6 Q left). (Scient Am. 71 and 90)

*** A good indication that the estimates are about right ***

So the problem is: Can we smooth out the peak and ease our way into a situation free from reliance on oil as a fuel as painlessly as possible?

OIL RESOURCES 9Future changes to the estimate

Huge undetected deposits: unlikely as massive exploration covered most of the globe. Only poles and deep ocean and much of deep ocean has been shown to be barren.

New Technology: Increased technology increases fraction of oil recovered from each field. Advanced recovery methods will buy a little more time before the fall. However, this is often misleading as oil companies build technological developments into their estimates. Also is the Middle east advanced techniques are little help as oil flows from a bore naturally (primary recovery).

Secondary Recovery: pressurised water pumped into a reservoir to expel oil (inc in estimate).

Tertiary Recovery:

- adding polymers to water to change flow patterns and increase expulsion.

- Setting fire to oil in situ to raise pressure and reduce viscosity. These add a further 2Q.

- Tar sands and shale deposits. Vast reserves in Canada, Venezuela, former Soviet Union and NW Colorado. Must be mined, heat treated not drilled. There are large environmental problems with this treatment including vastly increased air and water pollution, heavy metal contamination and vast slurry production.

C+L estimate (sceptically) that only 700 Gbo are recoverable (4 Q)

OIL RESOURCES 10So where does this leave us?

The Energy Information Administration forecasts oil demand rising by 60 % before 2020.

Increase in political tension: return to large market shareof Middle east OPEC states.

Largest fields will also peak last.

This may curb demand on its own. However, by 2010 even Middle East past its midpoint.

C+L warn that planning strategies for an oil free economy must begin now. They sum up by stating that:

“What our society does face however, is the end of abundant and cheap oil on which all industrial nations depend”

So our best estimate of the total remaining oil resource, R1, is 6 Q

Given enhanced technology and new findings etc C+L best guess at ultimate practical resource is 12 Q

They say their estimates for tar and shale oil is pessimistic so lets take an ultimate practical resource estimate, R2, to be: 15 Q

The ultimate resource value, R∞ could range from 14 Q to 30 Q

GAS, COAL AND NUCLEAR RESOURCESThe estimated gas resource is similar to that of oil, however, much less has been exploited.

The use of gas as a fuel has great environmental advantages over other fossil fuels.

Emission of CO2 is significantly reduced, 40 % less than coal and 25 % less than oil for the same energy output. In addition gas fired power stations are relatively cheap to run.

In 1993 the cost of a gas fired power station was 2.2 p/kWh whereas the cheapest nuclear plant was 5 p/kWh. A coal station was somewhere between these two.

In 1993 the USGS gave estimates for oil and gas in units of Q (Gbo in brackets).OIL GAS

Cumulative Production 4.1 (699) 1.7 (292)Identified (discovered) reserves 6.5 (1103) 5.0 (856)Undiscovered conventional resources 2.8 (471) 4.6 (780)Future resources 9.3 (1574) 9.6 (1636)Total resources 13.4 (2273) 11.4 (1928)

As you can see the figures are similar. The figure given by the USGS for the future oil resource was higher than our R1 estimate by 50 %, however, as we saw this made little difference to the overall argument. So we’ll take 10 Q as our R1 estimate for gas.R1 is the estimate assuming conventional technology and costs.

GAS RESOURCES 2Our R2 estimate for oil is 15 Q.

Given that the USGS estimates for gas are similar to those for oil we might postulate a similar R2 value.

However, we have already said that gas is considerably well developed. In addition, the existing gas fields are close to areas of consumption because of difficulties with transportation.

Bearing this in mind we could opt for a larger R2 estimate for gas, say 20 Q.

There are also huge deposits of methane in solid hydrated form. They are often found by oil drillers at medium depths, particularly under the arctic permafrost.

Estimates of these methane hydrates are highly uncertain, some have been extremely large.

In any case, we currently do not have the technology to recover this resource.

As a result, it is difficult to be certain about R2 and even harder to put a figure on R∞.

Let us assume a value of R∞ of 600 Q for the gas and oil total.

COAL RESOURCESEstimates of the total reserves of coal based on an analysis of known abundances gives a value of 280 Q for the global reserve, or 140 Q allowing for the 50 % extraction efficiency.

This compares well with a 1990 Scientific American article estimate of 150 Q.

However, other estimates are much larger e.g. Dorf gives a value of 400 Q. Let us be generous and give R2 = 500 Q.

Shown below are world production projections for coal given two estimates for the total resource (7.6 x 1012 and 4.3 x 1012 tons or 190 and 107 Q).

5

4

3

2

1

0

Ann

ual P

rodu

ctio

n Q

/yea

r

2600240022002000Year

190 Q107 Q

COAL RESOURCES 3It is clear that there is an abundant supply of coal until at least well into the 24th century.

However, there are several major drawbacks will coal:

1. Coal is a “dirty” fuel: Apart from the already discussed problem of coal producing CO2 much more efficiently per J of energy released than either gas or oil, coal has a high sulphur content. This is emitted as sulphur dioxide (SO2) in the combustion process. Flue Gas Desulphurisation (FGD) has now been fitted on new coal fired power stations in most industrialised countries, reducing the emission levels. FGD is, however, expensive to implement and maintain.

2. Fly ash is removed at source electrostatically, however, a 1000 MW power plant will require 2.5 hectares of land annually for disposal if it is piled to a height of 7.5 m.

3. Groundwater contamination: ground water may become contaminated by acidification from mining activities.

4. Effects on the surface: Refuse and spoil banks, surface subsidence, erosion and strip pits.

FISSION RESOURCESA cost limit of $15 per lb of Uranium ore U3O8 is widely used.

However, accurate estimates of Uranium reserves are difficult to come by and believe.

Several countries are not willing to publicise even their own reserves.

The energy delivery per unit mass of fuel is also dependent on the type of reactor used.

A fast breeder reactor, in which the principle isotope U238 is converted to Pu239 increases the energy yield over a conventional thermal reactor by a factor of 60.

The estimated current resource R1 is around 4 Q. (250 Q if fast breeder).

However, the consensus is that the ultimate resource will be much larger, typically 100 Q for thermal and 6000 Q for fast breeder reactors.

The total amount of Uranium in the accessible part of the Earth’s crust is equivalent to about 108 Q.

This is not realistically useable as most is in very dilute form, so dilute that the energy used in extraction would be greater than the yield energy.

DRAWBACK: Potential major health and environmental problems (perception).

FUSION RESOURCESFusion resources depend on feasibility. If deuterium alone can be used as a fuel the

amount available in naturally occurring water would be equivalent to about 1010 Q, in this case a realistic figure as the cost of extraction is trivial.

If, as seems likely, fusion is restricted to a mixture of deuterium and tritium then the limiting resource is lithium from which the tritium is obtained by nuclear reactions such as: Li6 + n -> He4 + H3 (H3 is tritium).

The known reserves of tritium have been evaluated as equivalent to an energy production of around 200 Q.

This is a very vague estimate and almost certainly a minimum as exploration for Lithium has not been an issue to date.

Better estimates than this are not available.

SUMMARY OF RESOURCESThis table provides three figures for each fuel type.

R1 = estimate of resource at present costs and technology.

R2 = best guess at ultimate resource with reasonably extrapolated technology.

R3 = the “natural limit”.

R1 R2 R∞

FOSSIL FUEL OIL 6 Q 15 Q ?> oil, gas,

GAS 10 Q 20 Q ?> combined > 600 Q??

COAL 33 Q 500 Q 107 Q ??

FISSION THERMAL 4 Q 100 Q ? Approx.

BREEDER 250 Q 6000 Q? 108 Q

FUSION DD (unlikely to be practical) 1010 Q 1010 Q

DT 200 Q > 200 Q ?

Natural Energy Flows – Alternative Resources

Mean Solar Input 5000 Q/year

Earth

Atmosphere

Photosynthesis 1 Q/y

Reflected radiation (albedo 30%) 1500 Q/y

Absorption and re-radiation 2350 Q/y

Evaporation and precipitation 1300 Q/y

Solar power assoc. with winds waves and currents 12 Q/y

Geothermal outflow from Earth ~ 1 Q/y

Mean tidal power assoc with Earth-Sun-Moon ~ 0.1 Q/y

Summary of Alternative Resources

All power units in Q/year Present Estimated NaturalInstalled Maximum EnergyCapacity Potential Flow

Power Density S1 S2 S∞MW/km2

Hydropower n/a 0.01 0.1 1.3

Wind 1-10 Small 0.2 12

Waves 20 v small 0.02 0.2

Tides n/a small 10-3 0.1

Geothermal n/a 10-4 10-3 1

Solar 15 Small 4.5? 900 (land only)

Biomass 0.4 ? 0.15 1.3

TOTAL 0.01 ~5 ~916

SUMMARY OF ENERGY ALTERNATIVES

We estimated that at the end of the period of world population growth and stabilisation of energy usage (2080) we would be using 5 Q/year.

Oil and Gas Resources: finite and small and likely to be exhausted before steady statereached.

Coal Resources: More plentiful but its use is restricted because of climate change impacts of increasing CO2 emission into the atmosphere.

Nuclear Power: Comparatively large and the resources are likely to last well beyond the period of change

Alternative Energy Sources: With the exception of Solar power we are limited to around 10% of the planning target of 5 Q/year.

It should be noted that as they deliver electricity directly through turbines they replace about 3 times the fossil fuel they replace if used in the way as fossil fuel electricity generation is around 30% efficient.

So the remaining 3.5 Q/year must be met from Solar, or fission and fusion power generation.

Given no-one wants nuclear if we can help it we must look at whether solar power can deliver our requirements.