International Journal of Clean Coal and Energy, 2013, 2, 27-34
doi:10.4236/ijcce.2013.22B007 Published Online May 2013 (http://www.scirp.org/journal/ijcce)
Prospects for Coalbed Methane and Shale Gas in a
Carbon-Constrained World: A Preliminary Analysis
Takayuki Takeshita
Transdisciplinary Initiative for Global Sustainability, The University o f Tokyo, T okyo, Japan
Received April 16, 2013; revised June 2, 2013; accepted April 24, 2013
ABSTRACT
Using a regionally disaggregated global energy system model with a detailed treatment of the natural gas resource base,
this paper analyzes the competitiveness of coalbed methane and shale gas in the global primary energy mix and the
cost-optimal pattern of their production in regional detail over the period 2010-2050 under a constraint of halving global
energy-related CO2 emissions in 2050 compared to the 2000 level. It is first shown that neither coalbed methane nor
shale gas could become an important fuel in the global primary energy mix throughout the time horizon, although each
of them could become an important source of world natural gas production from around 2030 onwards. It is then shown
that unlike findings of previous studies, coalbed methane would be more attractive than shale gas as a primary energy
source globally under the CO2 constraint used h ere. The results ind icate that North America continues to be th e world’s
largest coalbed methane producer until 2030, after which China overtakes North America and retains this position until
2050. Also, India, Russia, South Africa, and Australia contribute noticeably to world coalbed methane production. The
results also indicate that North America continues to dominate world shale gas production until 2040, after which a
number of world regions, notably India, Europe, and China, begin to participate visibly in world shale gas production.
Keywords: Coalbed Methane; Shale Gas; CO2 Mitigation; Regionally Detailed Analysis; Global Energy System Model
1. Introduction
Driven by the unconventional gas revolution that has
taken hold in North America in recent years, world un-
convention al gas produ ctio n ha s been in creasing stead ily.
Already, the rapidly expanding development of uncon-
ventional gas has reshaped the US gas market and sub-
stantially affected the global gas market. Given the large
resource base of unconventional gas and the growing
demand for affordable, clean natural gas worldwide, this
trend is likely to continu e in the fu ture. As a consequence,
it is well possible that unconventional gas will become
one of the most important fuels in the future global pri-
mary energy mix, and that unconventional gas produc-
tion will have a huge impact on the future global energy
landscape.
Under these circumstances, unconventional gas and its
prospects are receiving significant attention globally.
Thus, several studies hav e so far constructed quantitative
scenarios of future unconventional gas production.
Among all previous related studies, the special report in
the International Energy Agency’s (IEA) World Energy
Outlook 2011 [1] seems to be the most elaborate one. It
presented projections of world natural gas production by
region and world natural gas production by type through
to 2035. It obtained two important findings relating to
unconventional gas production. First, the share of un-
conventional gas in total global gas supplies will rise
continuously, reaching 24% in 2035. Second, most of the
increase in unconventional gas production comes from
shale gas and coalbed methane.
However, there are some drawbacks in this IEA study.
First, projections were performed without the interna-
tional target to avoid dangerous climate change. The re-
sults of the projections suggest the long-term global av-
erage temperature rise of over 3.5 degrees Celsius above
pre-industrial levels. Second, it does not provide a re-
gional split of the production of each type of unconven-
tional gas over the projection period. Third, projections
were performed over the period to 2035 , so it is unable to
assess the long-term prospects for unconventional gas.
In this context, this paper explores the prospects for
coalbed methane and shale gas in regional detail over the
period to 2050 under a stringent climate stabilization
constraint (i.e., a halving of global energy-related CO2
emissions in 2050 compared to the 2000 level). In the
first step, the competitiveness of coalbed methane and
shale gas in the global primary energy mix under this
constraint is assessed over the long term. In the second
step, the cost-optimal global pattern of their production
under this constraint is derived in regional detail over the

T. TAKESHITA
28
long term. Due to space limitations, the focus of this pa-
per is confined to the competitiveness of coalbed meth-
ane and shale gas and their production pattern only.
These analyses are done by using a regionally disaggre-
gated global energy system model with 70 regions
(REDGEM70) [2 ,3], which is characterized by a detailed
technological representation.
2. Methodology
2.1. Overview of the REDGEM70 Model
REDGEM70 is a technology-rich, bottom-up global en-
ergy systems optimization model formulated as an in-
tertemporal linear programming problem (see [3] for a
schematic representation of the structure of the model).
With a 5% discount rate, the model is designed to deter-
mine the cost-optimal energy strategy (e.g., the cost-op-
timal choice of technologies and fuels) from 2010 to
2050 at 10-year intervals for each of 70 world regions so
that total discounted global energy system costs are
minimized under constraints on the satisfaction of exo-
genously given energy end-use demands, the availability
of primary energy resources, material and energy bal-
ances, the maximum market growth rates of new tech-
nologies and fuels, etc. In the model, price-induced en-
ergy demand reductions and energy efficiency improve-
ments, fuel switching to less carbon-intensive fuels, and
CO2 capture and storage in geologic formations are the
three options for CO2 emissions reduction.
Furthermore, in the current version of the model used
in this study, there is also a constraint that global en-
ergy-related CO2 emissions in 2050 are to be halved
compared to the 2000 level. This constraint is imposed
because the Intergovernmental Panel on Climate Change
(IPCC) has concluded that a 50% to 80% reduction of
global CO2 emissions by 2050 compared to the 2000
level can limit the long-term global mean temperature
rise to 2.0 degrees Celsius above pre-industrial levels [4],
which is now recognized as the ultimate goal by most
world leaders and experts. The model has a full flexibil-
ity in where and how CO2 emissions reduction is
achieved to meet this constraint.
As described above, REDGEM70 uses 70 world re-
gions. Figure 1 shows how the 70 world regions are de-
fined in the model. These 70 regions are categorized into
“energy production and consumption regions” and “en-
ergy production regions”. The whole world was first di-
vided into the 48 energy production and consumption
regions to which future energy end-use demands are al-
located. The 22 energy production regions, which are
defined as geographical points, were then distinguished
from the energy production and consumption regions to
represent the geographical characteristics of the areas
endowed with large amounts of fossil energy resources.
While the 48 energy production and consumption regions
cover the global final energy consumption, all the en-
ergy-related activities except final energy consumption
are conducted in each of the two region types in the
model. Such a detailed regional disaggregation enables
the explicit consideration of regional characteristics in
terms of energy resource supply, energy demands, geog-
raphy, and climate.
Representative cities in energy production and consumption regions
Representative s ites in energy production regions
Figure 1. Regional disaggregation of REDGEM70.

T. TAKESHITA 29
Future trajectories for energy end-use demands were
estimated as a function of those for socio-economic
driving forces such as population and income in the in-
termediate B2 scenario developed by [5]. Allocation of
the energy end-use demand estimates to the 48 energy
production and consumption regions was done by using
country- and state-level statistics/estimates (and projec-
tions if available) on population, income, geography,
energy use by type, and transport activity by mode, and
by taking into account the underlying storyline of the B2
scenario that regional diversity might be somewhat pre-
served throughout the 21st century.
Assumptions on the availability and extraction cost of
fossil energy resources and uranium resources were de-
rived from [6] and [7], respectively. A detailed descrip-
tion of the modeling of the natural gas resource base is
given in Section 2.2. There is one important note regard-
ing the treatment of exhaustible resources in this model-
ing analysis. To avoid excessive exploitation of ex-
haustible primary energy resources in the first h alf of the
century, the model was actually run over the period
2010-2100, and then the results of this simulation are
shown for the period 2010-2050.
For non-biomass renewable resources, electricity sup-
ply potentials and electricity generation costs by world
region are exogenous inputs to the model, which were
obtained from [8,9]. For biomass resources, the model
considers not only terrestrial biomass, but also waste
biomass. Data for these biomass resources are provided
in [10]. These resource availability estimates were then
allocated to the 70 model regions by using country-,
state-, and site-level statistics/estimates.
REDGEM70 considers the entire supply chain of
natural gas, which includes natural gas production, inter-
regional natural gas transportation by pipeline or lique-
fied natural gas tanker ship, natural gas storage, its con-
version into secondary energy, intraregional natural gas
distribution, and its final supply at retail sites. In the
model, natural gas can be converted into high- and low-
temperature heat, electricity, hydrogen, methanol, di-
methyl ether, and Fischer-Tropsch synfuels. It can also
be used as a fuel for road vehicles (excluding motorized
two-wheelers), large ships, and aircraft and feedstock for
industrial use.
2.2. Modeling of the Natural Gas Resource Base
In addition to conventional gas, REDGEM70 considers
three types of unconventional gas, including coalbed
methane, shale gas, and other unconventional gas such as
tight gas and deep gas. Gas hydrates are not included
because it is presently unclear if and when their potential
can ever be used [11]. The resource base estimates of
conventional gas and these three types of unconventional
gas by each of 18 world regions are taken from [6]. Fur-
thermore, the estimates of the potential for enhanced
coalbed methane (ECBM) recovery from CO2 injection by
each of seven world regions are taken from [12,13]. The
global resource base of conventional gas, coalbed methane,
shale gas, and other unconventional gas amounts to
12,213 exajoules, 7,520 exajoules, 9,281 exajoules, and
13,016 exajoules, respectively.
The conventional gas resource base estimates by each
of 18 world regions were allocated to the 70 model re-
gions by using data from [11,14,15]. The stepwise supply
cost curves of conventional gas (consisting of three steps)
were then developed for each of the 70 model regions
from global and regional data on the range of conven-
tional gas productio n costs, which do not includ e taxes or
royalties [1,6,16-18]. Figure 2 illustrates the resulting
aggregate global conventional gas supply cost curve.
Following the approach taken by [16], the coalbed
methane resource base estimates (including those of the
potential for ECBM recovery from CO2 injection) by
each world region were allocated to the 70 model regions
by linking its regional distribution to that of the anthra-
cite and bituminous coal resource base, which was esti-
mated from [12,19,20]. Similar to the development of the
conventional gas supply cost curves above, the stepwise
supply cost curves of coalbed methane (consisting of
three steps) were then developed for each of the 70 mod-
el regions from global and regional data on the range of
coalbed methane production costs, which do not include
taxes or royalties [1,6,12,13,16-18]. Regional variation in
production costs of coalbed methane (excluding ECBM)
was estimated using regional data on them [1,16,18] and
assuming that they are lower for regions with rich coal-
bed methane production experience (implying the exis-
tence of production skills and supply infrastructure) and
the large coalbed methane resource base. Figure 2 illus-
trates the resulting aggregate global coalbed methane
supply cost curve.
0
5
10
15
20
03000 6000 90001200015000
Pr oductioncost(US$
2000
/GJ)
EJ
0
5
10
15
20
03000 6000 90001200015000
Pr oductioncost(US$
2000
/GJ)
EJ
0
5
10
15
20
03000 6000 90001200015000
Pr oductioncost(US$
2000
/GJ)
EJ
0
5
10
15
20
03000 6000 90001200015000
Pr oductioncost(US$
2000
/GJ)
EJ
Coalbed
methane
Conventionalgas
Other
unconventionalgas
Shalegas
Figure 2. Aggregate world supply cost curves for conven-
tional and unconventional natural gas.

T. TAKESHITA
30
For shale gas, a lack of comprehensive world-wide
resource potential data makes it difficult to derive accu-
rate estimates of the regional distribution of its resource
base by the 70 model regions. Specifically, there seem
not to be reliable shale gas resource potential data for
regions except the US and the 32 countries examined by
[21]. Accordingly, the estimates of the shale gas resource
base in the US taken from [6] were allocated to the six
US regions of the model by using data from [18,22,23].
On the other hand, the estimates of the shale gas resource
base in the other world regions taken from [6] were allo-
cated to the 64 model regions by using data from [21,22]
and by following the assumption made by [16] that its
regional distribution is linked to that of the in-place shale
volume given by [16]. The stepwise supply cost curves
of shale gas (consisting of three steps) were then devel-
oped for each of the 70 model regions from global and
regional data on the range of shale gas production costs,
which do not include taxes or royalties [1,6,16-18,23].
Regional variation in shale gas production costs was es-
timated using regional data on them [16,18,23] and as-
suming that they are lower for regions with rich shale gas
production experience. Figure 2 illustrates the resulting
aggregate global shale gas supply cost curve.
Following the approach taken by [16], th e estimates of
the other unconventional gas resource base by each of 18
world regions were allocated to the 70 model regions by
linking its regional distribution to that of the conven-
tional gas resource base. The stepwise supply cost curves
of other unconventional gas (consisting of three steps)
were then developed for each of the 70 model regions
from global and regional data on the range of its produc-
tion costs, which do not include taxes or royalties
[1,6,16-18]. Regional variation in its production costs
was estimated using regional data on them [1,16,18] and
assuming that they are lower for regions with rich pro-
duction experience of other unconventional gas and its
large resource bases. Figure 2 illustrates the resulting
aggregate global supply cost curve of other unconven-
tional gas.
In the last step, royalties are added to gas production
costs described above. Royalties from gas production
were estimated at US$2000 0.59 per gigajoule of gas,
compared to US$2000 1.77 per gigajoule of crude oil and
US$2000 0.44 per gigajoule of coal [19]. This sum is re-
garded as actual gas production costs and is used as an
exogenous inpu t to the model. In the model, taxes are no t
included as part of energy system costs.
3. Results and Discussion
3.1. Competitiveness of Coalbed Methane and
Shale Gas
Figure 3 shows the evolution of the world total primary
0
100
200
300
400
500
600
700
800
20102020203020402050
Worldtotalprimaryenergysupply(EJ/year)
Solar
Wind
Geo thermal
Hydro
Biomass
Nu clear
Otherunconv.gas
Shalegas
Coalbedme th a n e
Conv.naturalgas
Crudeoil
Coal
Figure 3. World total primary energy supply.
energy supply (TPES). The substitution accounting
method is used for reporting TPES. It can be seen that
natural gas continues to be an important primary energy
source throughout the time horizon. The share of natural
gas in the world TPES overtakes that of coal by 2020 to
become the second-most important fuel in the global
primary energy mix from 2020 onwards. The share of
natural gas in the world TPES increases until 2030 but
begins to decrease thereafter, reaching 18.4% in 2050.
Also, in absolute terms, world natural gas production
reaches its peak in 2030 with a slightly declining trend
thereafter. Under the stringent CO2 emissions reduction
constraint, non-fossil fuels (such as nuclear and renew-
ables) account for an increasing share in the world TPES
at the expense of fossil fuels.
Although the share of unconventional gas in world
natural gas production is small in the early time periods,
unconventional gas becomes increasingly competitive
over time. Its share of world natural gas production in-
creases from 15.1% in 2010 to 44.6% in 2050, implying
that about half of world natural gas production comes
from unconventional sources in 2050. Such an increased
participation of unconventional gas leads to an increase
in its share of the global primary energy mix: the share of
unconventional gas in the world TPES increases from
3.3% in 2010 to 9.8% in 2040 and then decreases to
8.2% in 2050. This decline in the share of unconven-
tional gas in 2050 is due to the declining share of natural
gas in the world TPES in the second half of the time ho-
rizon. It can therefore be argued that unconventional gas
could constitute one of the pillars of the global primary
energy mix from around 2030 onwards.
Among all types of unconventional gas sources, other
unconventional gas (mainly tight gas) has the largest
share of world un convention al gas pro duction un til 2020 .
After that, coalbed methane continues to be the most
important unconventional gas source worldwide: its
share of world natural gas production increases from
2.7% in 2010 to 19.4% in 2050. Over the period 2040-

T. TAKESHITA 31
2050, shale gas remains the second-most important un-
conventional gas source worldwide: its share of world
natural gas production increases from 4.3% in 2010 to
12.0% in 2050.
This finding is different from that of previous studies
(e.g., [1]), which projected that shale gas would become
the largest unconventional gas source worldwide from
around 2020 onwards. However, the above finding of
this study is plausible for three reasons. First, as shown
in Figure 2, the production cost of coalbed methane is
almost the same or even slightly lower than that of shale
gas, as long as their cumulative production throughout
the time horizon is b elow the level achieved in this study
(i.e., 799.7 EJ for coalbed methane and 523.5 EJ for
shale gas). Second, under the stringent CO2 emissions
reduction constraint, CO2 is priced at a sufficient level to
offset part of the production cost of ECBM recovery us-
ing CO2 sequestration, which makes coalbed methane
production attractive. In fact, the results show that CO2-
ECBM is developed on a large scale from the initial
stage of coalbed methane production. Third, China and
India are projected to account for a significant share of
world natural gas demand in the long term toward 2050
(e.g., [1,24]), and these countries are estimated to be en-
dowed with much larger amounts of the coalbed methane
resource base than those of the shale gas resource base
[6]. Therefore, the supply of coalbed methane is more
cost-effective than that of shale gas in these countries
because of the low demand for gas transportation, which
represents a large share of total natural gas supply cost.
It is important to note that coalbed methane and shale
gas play only marginal roles in the world TPES, as
shown in Figure 3. The share of coalbed methane and
shale gas in the world TPES increases from 0.6% in 2010
to 3.6% in 2050 for the former and from 0.9% in 2010 to
2.2% in 2050 for the latter. To summarize, these results
mean that neither coalbed methane nor shale gas would
become one of the important fuels in the global primary
energy mix over the period to 2050 under the stringent
CO2 emissions reduction constraint, although each of
them would have a large share of world natural gas pro-
duction from around 2030 onwards under this constraint.
3.2. Cost-Optimal Pattern of Coalbed Methane
and Shale Gas Production
Figures 4 and 5 show the regional breakdown of the
world production of coalbed methane and shale gas, re-
spectively. The regional classification used in this study
is identical to that of [5]. North America (predominantly
the US) continues to be the biggest supply source of coal-
bed methane until 2030. After that, Centrally Planned
Asia (predominantly China) overtakes North America to
become the world’s largest coalbed methane producer.
From around 2030 onwards, coalbed methane production
0
5000
10000
15000
20000
25000
30000
2010 2020 2030 2040 2050
Worldcoalbedmet haneproduction(PJ/year)
PacificOECD
OtherPacificAsia
SouthAsia
CentrallyPlannedAsia
Sub‐SaharanAfrica
Midd leEast&NorthAfrica
FormerSovietUnion
East ern Eu ro pe
WesternEuro pe
LatinAmerica
NorthAmerica
Figure 4. World coalbed methane production by the 11 world
regions.
0
5000
10000
15000
20000
25000
30000
2010 2020 2030 2040 2050
Worldshale gasproduction(PJ/year)
PacificOECD
OtherPacificAsia
SouthAsia
CentrallyPlannedAsia
Sub‐Sah aranAfrica
MiddleEast &No rth Africa
FormerSovietUni on
Eas ternEuro pe
WesternEurope
LatinAmerica
No rth America
Figure 5. World shale gas p roduction b y the 11 world reg ions.
becomes more spatially dispersed. Besides North Amer-
ica and Centrally Planned Asia, South Asia (predomi-
nantly India), the Former Soviet Union (predominantly
Russia), Sub-Saharan Africa (predominantly South Africa),
Western Europe, and Pacific OECD (predominantly
Australia) make a noticeable contribution to world coal-
bed methane production.
In contrast, North America (predominantly the US)
continues to dominate world shale gas production
throughout the time horizon. However, a number of
world regions, notably South Asia, Western Europe,
Eastern Europe, and Centrally Planned Asia, begin to
have a visible participation in world shale gas production
around 2040. The combined share of the world regions
except North America in world shale gas production
reaches only 39.3% in 2050. This implies that the US is
likely to retain its position as the world’s largest shale
gas producer at least until the middle of th e century.
Now, the results are described in more regional detail.
As an example, Figure 6 shows the world natural gas
producti o n by region and by s ource for 205 0.

T. TAKESHITA
32
4. Conclusions
The cost-optimal pattern of coalbed methane produc-
tion at the regional level is summarized as follows. In
2020, there are five major coalbed methane-producing
regions in the world: 1) basins in the Rocky Mountains
(e.g., San Juan, Raton, and Powder River), 2) the West-
ern Canadian Sedimentary Basin (including Alberta and
British Columbia), 3) the northern and central Appala-
chian basins, 4) basins in northern China (e.g., Ordos and
Qingshui), and 5) basins in eastern Australia. In 2030,
besides the above regions, eastern India and South Africa
become major coalbed methane-producing regions in the
world. In 2040, central, eastern, and western China (e.g.,
Junggar), Russia (e.g., Kuznetsk), western and southern
India, and the southern part of Africa except South Af-
rica (e.g., Botswana) join the major coalbed meth-
ane-producing regions in the world, and some European
countries (e.g., Germany and Czech Republic) join them
in 2050 as shown in Figure 6.
In this paper, the regionally disaggregated global energy
system model with a detailed treatment of the conven-
tional and unconventional natural gas resource base has
been used to explore the long-term prospects for coalbed
methane and shale gas in regional detail over the period
to 2050 under the constraint of halving global energy-
related CO2 emissions in 2050 compared to the 2000
level. Their competitiveness in the global primary energy
mix under this constraint has first been assessed over the
period to 2050. The cost-optimal pattern of their produc-
tion under this constraint has then been derived in re-
gional detail over the per iod to 2050. The major findings
and implications can be summarized as follows.
First, neither coalbed methane nor shale gas could be-
come an important fuel in the global primary energy mix
over the period to 2050 under the stringent CO2 emis-
sions reduction constraint. The share of coalbed methane
and shale gas in the world TPES would increase over
time but reach only 3.6% and 2.2%, respectively, in 2050.
However, each of them would become an increasingly
important source of world natural gas production over
time. The share of coalbed methane and shale gas in
world natural gas production would increase over time
and reach 19.4% and 12.0%, respectively, in 2050 .
On the other hand, the cost-optimal pattern of shale
gas production at the regional level is summarized as
follows. Over the period to 2030, the southeastern and
northeastern parts of the US (e.g., Barnett, Haynesville,
Fayetteville, Woodford, and Marcellus) dominate world
shale gas produ ction, while small-scale shale gas produc-
tion is carried out in the Western Canadian Sedimentary
Basin (e.g., Horn River and Montney) and basins in the
Rocky Mountains. In 2040, besides the above regions,
India (e.g., West Bengal), inland central China (i.e., Si-
chuan), South Africa (i.e., Karoo), and some European
countries (e.g., France and Poland) become major shale
gas-producing regions in the world. In 2050 as shown in
Figure 6, other European countries and the southern part
of Latin America (e.g., Argentina) join them.
Second, in contrast to findings of previous studies,
coalbed methane would become a more attractive fuel
than shale gas at the global level from around 2020 on-
wards. One main reason is that CO2-ECBM techniques
would be deployed on a large scale as a means of reduc-
ing CO2 emissions under the stringent CO2 emissions
reduction constraint, which would provide a great incen-
tive for increased coalbed methane production. Another
Figure 6. World natural gas production by region and by source in 2050a.
a. Towers in dicat e repr esentat ive s ites in energ y produ ction r egion s, whil e cross es indi cate rep resen -
tative citie s in energy production and consumpti on regions.

T. TAKESHITA 33
main reason is that the world’s major coalbed meth-
ane-rich regions are located geographically close to the
world’s major natural gas consumption regions (i.e.,
China and India). This helps to reduce natural gas trans-
portation cost and to improve the overall economics of
natural gas supply.
Third, in the cost-optimal coalbed methane production
pattern derived from the model, North America (mainly
the Rocky Mountain and Appalachian regions of the US)
remains the world’s largest coalbed methane producer
until 2030, after which Centrally Planned Asia (mainly
northern China) overtakes North America and continues
to be the world’s largest coalbed methane producer.
From around 2030 onwards, South Asia (mainly eastern
India), the Former Soviet Union (mainly Kuznetsk),
Sub-Saharan Africa (mainly South Africa), and Pacific
OECD (mainly eastern Australia) also contribute no-
ticeably to world coalbed methane production. On the
other hand, in the cost-optimal shale gas production pat-
tern derived from the model, North America (mainly the
southeastern and northeastern parts of the US) continues
to dominate world shale gas production until 2040. After
that, South Asia (mainly India), Western and Eastern
Europe (mainly Poland and France), and Centrally
Planned Asia (mainly Sichuan) also participate visibly in
world shale gas production.
It must be emphasized that coalbed methane and shale
gas could play a substantial role in diversifying natural
gas supply sources, and thus in improving energy secu-
rity. The widespread market penetration of coalbed meth-
ane and shale gas could make a large contribution to re-
ducing the world’s dependence on conventional gas in
the Middle East and Russia. They have a potential for
representing the most part of natural gas supply in coun-
tries such as the US, China, and India in the long term. It
should be noted, however, that not only the realization of
the potential for coalbed methane and shale gas outside
North America, but also their ever increasing production
in North America remains actually highly uncertain. To
receive the full benefits of coalbed methane and shale gas,
numerous obstacles (such as large volumes of water use,
negative environmental impacts, and safety risks) must
be overcome.
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