The Republic of the Philippines Coalbed Methane

Assessment: Based on Seventeen High Pressure 

Methane Adsorption Isotherms

Open-File Report 2006-1063

U.S. Department of the Interior

U.S. Geological Survey
The Republic of the Philippines Coalbed 

Methane Assessment: Based on 

Seventeen High Pressure

Methane Adsorption Isotherms

By Romeo M. Flores, Gary D. Stricker1, Ramon F. Papasin, Ronaldo R. Pendon2, 

Rogelio A. del Rosario2, Ruel T. Malapitan2, Michael S. Pastor2, Elmer A. Altomea2, 

Federico Cuaresma2, Armando S. Malapitan2, Benjamin R. Mortos2, and Elizabeth 

N. Tilos2



U.S. Geological Survey, Denver Colorado



Philippine Department of Energy, Metro Manila, Philippines

Prepared in cooperation with the

Republic of the Philippines

Department of Energy

Energy Resources Develpment Board

Geothermal and Coal Resources Development Division

Ft. Bonifacio, Taguig 1201

Metro Manila, Philippines

Open File Report 2006–1063

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2006

Posted online March 2006

Version 1.0

This publication is only available online at

http://www.usgs.gov/of/2006/1063

For more information on the USGS--the Federal source for science about the Earth, its natural and living resources, 

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Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Flores, R.M., Stricker, G.D., Papasin, R.F., Pendon, R.R., del Rosario, R.A., Malapitan, R.T., Pastor, M.S., Altomea, E.A., 

Cuaresma, F., Malapitan, A.S., Mortos, B.R., and Tilos, E.N., 2006. The Republic of the Philippines coalbed methane 

assessment: based on seventeen high pressure methane adsorption isotherms: U.S. Geological Survey Open−File 

Report 2006-1063.
iii

Contents

Introduction.....................................................................................................................................................1

Coal Geology of Studied Philippine Coal Districts....................................................................................1

Batan Island Coal District....................................................................................................................1

Catanduanes Coal District ..................................................................................................................2

Cagayan-Isabella Coal District ..........................................................................................................2

Cebu Coal District .................................................................................................................................2

Cotabato Coal District ..........................................................................................................................3

Negros Coal District ............................................................................................................................4

Samar (Excluding Leyte) Coal District ..............................................................................................4

Semirara (Excluding Mindoro) Coal District.....................................................................................4

Surigao Coal District ............................................................................................................................4

Zamboanga Sibuguey Coal District ...................................................................................................4

Methods of Sampling ....................................................................................................................................4

Discussion of Results....................................................................................................................................5

Coal Quality............................................................................................................................................5

Adsorption Isotherm ............................................................................................................................8

Potential Coalbed Methane Resources ...................................................................................................12

Estimates from Studied Coal Districts.............................................................................................12

Estimates From Other Coal Districts ...............................................................................................12

Recommendations for Future Study ................................................................................................16

References Cited..........................................................................................................................................16

Appendix.......................................................................................................................................................A1

Figures

1. Coal districts of the Philippines containing lignite to semi-anthracite coal in strata 

ranging from Eocene to Pleistocene in age.............................................................................2

2. Locations of coal samples from various Philippine coal districts that were analyzed

by the U.S. Geological Survey.....................................................................................................3

3. Photograph of a dipping coal-bed outcrop in Catanduanes coal district...........................5

4. Photograph of an inclined shaft of an active underground mine in the

Cebu coal district..........................................................................................................................6

5. Photograph showing trenching at an outcrop in Catanduanes coal district for

collecting coal samples...............................................................................................................6

7. Photograph of drilling rig used by Semirara Mining Corporation to core coal in the

Panian coalfield in the Semirara coal district..........................................................................7

6. Photograph illustrating the preparation of a coal sample, immediately following

collection, for shipment to laboratory .......................................................................................7

8. Coal core recovery from the Panian coalfield in the Semirara coal district ......................8

9. Plot of adsorbed methane versus apparent rank of Philippine coal samples..................13

10. Plot of adsorption isotherms versus equilibrium pressure of coal samples in the

Semirara coal district and in the Powder River Basin, Wyoming, USA ............................14
iv

11. The potential minimum coalbed methane in-place resources estimated for

Philippines coal districts based on ideal gas storage capacity .........................................15

Tables

 1. Summary of apparent rank and Langmuir parameters of

 Philippine coal samples......................................................................................................9

 2. Coal chemistry for samples utilized in construction of the Philippine isotherm 

curve ....................................................................................................................................10

3. Coal chemistry for samples utilized in construction of the Philippine isotherm 

curve ....................................................................................................................................11
Introduction

The Republic of the Philippines has some 19 coal 

districts that contain coal deposits ranging from Eocene to 

Pleistocene in age. These coal districts include: (1) Catanduanes (Eocene); (2) Cebu, Zamboanga Sibuguey, Bukidnon, 

Maguindanao, Sarangani, and Surigao (Oligocene to Miocene); (3) Batan Island, Masbate, Semirara (including Mindoro), and Quezon-Polilio (lower-upper Miocene); (4) Davao, 

Negros, and Sorsogon (middle-upper Miocene); (5) Cotabato 

(lower Miocene-lower Pliocene), Cagayan-Isabella, and 

Quirino (upper Miocene-Pliocene); (6) Sultan Kudarat (upper 

Miocene-Pleistocene); and (7) Samar-Leyte (lower PliocenePleistocene) (fig. 1). In general, coal rank is directly related to 

the age of the deposits – for example, the Eocene coal is semianthracite and the Pliocene-Pleistocene coal is lignite. 

Total coal resources in these 19 coal districts, which are 

compiled by the Geothermal and Coal Resources Development Division (GCRDD) of the Department of Energy of the 

Philippines, are estimated at a minimum of 2,268.4 million 

metric tonnes (MMT) (approximately 2.3 billion metric tones; 

see fig. 1). The largest resource (550 MMT) is the subbituminous coal in the Semirara (including Mindoro) coal district, 

and the smallest (0.7 MMT) is the lignite-subbituminous coal 

in the Quirino coal district. The combined lignite and subbituminous coal resources, using the classification by GCRDD 

and including Semirara and Surigao coal districts, are about 

1,899.2 MMT, which make up about 84 percent of the total 

coal resources of the Philippines. The remaining resources are 

composed of bituminous and semi-anthracite coal. 

The subbituminous coal of Semirara Island in the Mindoro-Semirara coal district (fig. 2) is known to contain coalbed methane (CBM), with the coal being comparable in gas 

content and adsorption isotherms to the coal of the Paleocene 

Fort Union Formation in the Powder River Basin in Wyoming, USA (Flores and others, 2005). As a consequence, the 

presence of CBM in the Semirara coal led to the present study 

of determining the adsorption isotherms, or gas (CBM) holding 

or storage capacity, of coal beds of various ages from selected 

coal districts in the Philippines. Samples for the study were collected from the Batan Island, Catanduanes, Cagayan-Isabella, 

Cebu, Negros, Samar, Semirara, Cotabato, Surigao, and Malangas coalfield of the Zamboanga Sibuguey coal districts by five 

field geology teams from the GCRDD.

Coal Geology of Studied Philippine 

Coal Districts

The coals studied from Philippine coal districts vary in 

geologic age, coal rank, lithostratigraphy, and depositional 

environment. The structural settings also vary, from large to 

small, folded to faulted, downdropped basins and sub-basins 

some of which are bounded by mountain ranges. More importantly, the coal districts lie in small to large islands, some of 

which are parts of peninsulas. Locations of coal samples collected in the coal districts are shown in figure 2. 

Batan Island Coal District

The coal sample in the Batan Island coal district was collected from the middle Miocene Bilbao Formation. The formation consists, from bottom to top, of (1) the Lower Limestone 

Member – buff-colored conglomeratic, coralline limestone 

with scattered lenses of carbonaceous sandstone, siltstone, and 

shale; (2) the Galicia Sandstone – coarse and locally conglomeratic sandstone; (3) the Coal Measure – brown sandstone and 

carbonaceous shale with interbedded coal beds; and (4) the 

Upper Limestone Member – massive gray to white limestone. 

These rocks are interpreted to be deposited in paralic and 

shallow marine environments. The Batan Island is a part of a 

group of islands in a southeast-trending peninsula of Luzon 

(fig. 2). The island is structurally deformed into synclines and 

anticlines disrupted by a fault in the middle part of the island. 

The Republic of the Philippines Coalbed Methane 

Assessment: Based on Seventeen High Pressure 

Methane Adsorption Isotherms

By Romeo M. Flores, Gary D. Stricker1, Ramon F. Papasin, Ronaldo R. Pendon2, Rogelio A. del Rosario2, 

Ruel T. Malapitan2, Michael S. Pastor2, Elmer A. Altomea2, Federico Cuaresma2, Armando S. Malapitan2,

Benjamin R. Mortos2, and Elizabeth N. Tilos2

1

U.S. Geological Survey, Denver Colorado

2

Philippine Department of Energy, Metro Manila, Philippines
Catanduanes Coal District 

The coal sample in the Catanduanes coal district was 

collected from the Eocene Hitoma and Payo Formations. The 

formations consist of carbonaceous shale, siltstone, sandstone, and coal beds. The coals are in distinct beds, 0.3-1.5 m 

thick, and in stringers; those in the carbonaceous shales were 

deposited in a paralic environment. The coal measure is in a 

northeast-trending basin bounded by two northeast-trending 

faults. The beds are steeply dipping to almost vertical, having 

been deformed by faulting along both northeast and northwest 

trends (del Rosario and Pastor, 2005a). Catanduanes is an 

island, part of a group of islands in a southeast-trending peninsula of Luzon (fig. 2).

Cagayan-Isabella Coal District 

The coal samples from Cagayan-Isabella coal district 

were collected in the Pliocene-Pleistocene Ilagan Formation, 

which contains interbedded marine shale and sandstone in the 

lower part and coarse marine sandstone and continental, coalbearing sandstone and conglomerate in the upper part. The 

coal beds, as much as 2.5 m thick (BHP Engineering, 1999), 

are part of a sequence that was deposited in marine and paralic 

environments. The coal district is located in the Cagayan 

Basin in northern Luzon (fig. 2), which is a semi-arcuate elongated valley bounded on the east by the Sierra Madre, on the 

west by the Cordillera Mountains, and on the southeast by the 

Caraballo Mountains. 

Cebu Coal District

Coal samples from Cebu coal district were collected in 

the upper Oligocene Cebu Formation, upper Oligocene-lower 

Miocene Malubog Formation, and middle Miocene Calagasan 

Formation (Pendon and Tilos, 2005). These coal-bearing 

formations consist of interbedded sandstone, siltstone, and 

shale, and contain coal beds as much as 2 m thick. Some 

Figure 1. Coal districts of the Philippines containing lignite to semi-anthracite coal (rank determined by GRCDD using ASTM 

classification) in strata ranging from Eocene to Pleistocene in age. The coal samples (indicated by blue arrows) from 10 coal districts 

were re-analyzed for their apparent rank by the U.S. Geological Survey. The coal resources for each of the districts are indicated in 

million metric tonnes (MMT). Modified from Balce and others (2005).

 Philippines Coalbed Methane Assessment
marine limestones are present indicating deposition in coastal 

paralic environments. Cebu is in the Visayas group of islands 

(fig. 2) in the south-central part of the Philippines. The island 

is mainly comprised of pre-Cretaceous-Oligocene basement 

rocks (for example, volcanics, schists, andesite, and diorite), 

which are exposed in faulted areas in the central part of the 

island. The younger coal-bearing formations are distributed 

along the margins of these basement rocks.

Cotabato Coal District

Coal samples in the Cotabato coal district were collected in 

the southern part of Mindanao (fig. 2), in the Oligocene Siloay 

Formation (Papasin and Pendon, 2005). This coal-bearing formation is informally named the Daguma Cotabato coal deposits 

by Daguma Agro-Minerals, Inc. (“Daguma”), which holds the 

Coal Operating Contract for this area. Daguma described the 

Figure 2. Locations of coal samples from various Philippine coal districts that were analyzed by the U.S. Geological Survey.

Coal Geology of Studied Philippine Coal Districts 
unit as consisting of interbedded sandstone, mudstone, shale, 

limestone, and coal beds. The coal beds, ranging in thickness 

from 8 to 17.5 m, are in four coal zones within a 220-m-thick 

stratigraphic interval that lies in the southwestern part of the 

Cotabato Basin, which is a large basin encompassing most of 

central Mindanao (fig. 2). The basin was infilled mainly by 

siliciclastics, metasediments, and metavolcanics. The western 

part of the basin is bounded by the Daguma uplift.

Negros Coal District 

The coal sample from Negros coal district is from the 

lower Miocene Macasilao Formation (Pendon and Tilos, 

2005), which consists of interbedded shale, claystone, sandstone, conglomerate, coal, and limestone beds deposited in 

terrestrial environments interrupted by short periods of marine 

trangression and paralic environments. The coal, as much as 

5 m thick, is in moderately dipping beds (20 degrees). The 

district is in the boot-shaped island of Negros, directly west 

of Cebu in Western Visayas (fig. 2) and the coal deposits are 

located in the northern, northeastern, south-central, and southwestern parts of the island. 

Samar (Excluding Leyte) Coal District 

The coal samples from Samar coal district were collected 

in the Oligocene-lower Miocene Bagacay Formation (del 

Rosario and Pastor, 2005b). The formation consists of interbedded shale, siltstone, sandstone, and coal beds. The coal 

beds, which are as much as 3 m thick and flat-lying, contain 

shale partings. Samar Island is situated in the easternmost part 

of the Visayas (fig. 2) and the coal areas are in the southern 

part of the island.

Semirara (Excluding Mindoro) Coal District

The coal samples in the Semirara part of the SemiraraMindoro coal district were collected in the lower-middle 

Miocene Semirara Formation. The formation is divided into 

a Lower Member consisting of sandstone, siltstone, and coal 

beds; a Middle Member consisting of predominantly sandstone with minor beds of mudstone and coal beds; and an 

Upper Member consisting of argillaceous limestone. Coal beds 

are as much as 20 m thick and are mined for steam coal by 

Semirara Coal Corporation. The coal-bearing units are overlain by a marine limestone (Pliocene Buenavista Formation), 

which indicates probable deposition on a low-lying coastal 

plain drained by rivers followed by a marine transgression. 

The Semirara part of the coal district, which is situated south 

of Mindoro Island (fig. 2), includes the Panian, Himalian, and 

Unong coalfields. These coalfields are in a series of anticlines 

or an anticlinorium displaced by a series of southwest-northeast trending normal faults. Two of these faults are major 

displacements that subdivide the island into three blocks, each 

containing a coalfield.

Surigao Coal District 

Coal samples in the Surigao coal district were collected 

in the upper Oligocene-lower Miocene Pamaypayan Formation, which is a sequence of sandstone, siltstone, mudstone, 

and coal beds occupying a small basin in the eastern part of 

Mindanao (fig. 2).

Zamboanga Sibuguey Coal District

Coal samples in the Malangas coalfield of the Zamboanga Sibuguey coal district, located in the western part of 

Mindanao (fig. 2), were collected in the Lalat Member of the 

lower Miocene Lumbog Formation. This formation consists 

of lithic sandstone interbedded with subordinate mudstone, 

carbonaceous shale and mudstone, and coal beds. The coal 

beds, which are mined underground, range in thickness from 

0.6 to 4.3 m. The Lalat Member was deposited in fluvial and 

paralic environments, which were inundated intermittently by 

shallow marine transgressions. Strata in the Malangas coalfield are highly folded, faulted, and intruded by igneous rocks 

(for example, microdiorite) that locally baked the coal and 

surrounding rocks. 

Methods of Sampling

Coal samples were selectively collected in the following 

coal districts by the listed personnel of GCRDD: (1) CagayanIsabella – Ramon F. Papasin, Elmer A. Altomea, and Federico 

Cuaresma; (2) Catanduanes/Samar – Rogelio A. del Rosario 

and Michael Pastor; (3) Cebu/Negros – Ronaldo R. Pendon 

and Elizabeth N. Tilos; (4) South Cotabato/Sultan Kudarat 

– Ronaldo R. Pendon and Ramon F. Papasin; and (5) Surigao 

del Sur/Bislig – Ruel T. Malapitan, Armando S. Malapitan, 

and Benjamin R. Mortos. The samples were collected during 

fieldwork from July to September, 2005.

A total of seventeen coal samples were collected from 

outcrops and underground active and abandoned mines 

(figs. 3, 4). Fresh outcrop samples were obtained by digging 

trenches or test pits, 1-2 m deep, from which (fig. 5) 1 to 2 

kg of coal were collected. To retain their inherent moisture 

content, preparation for shipment to laboratory consisted of 

double bagging the coal sample, putting wet tissue in the 

plastic bags, and wrapping. Seven coal samples were collected 

from cores drilled in the Semirara coal district (figs. 7, 8).

The seventeen coal samples collected by GCRDD personnel were shipped by overnight carrier to the USGS in Denver, 

Colorado, USA for coal quality analyses and adsorption isotherms. The USGS then sent 250 to 300 g of each coal sample 

to a commercial testing laboratory for coal quality determination. Upon return of the analytical results, apparent ranks were 

calculated following the procedures of the American Society 

for Testing and Materials (ASTM, 1998; standards section D 

388-98). In addition, a sealed 200- to 300-g sample was sent to 

 Philippines Coalbed Methane Assessment
a commercial laboratory for high-pressure methane adsorption 

analysis (see Adsorption Isotherm section). Samples with 

duplicate apparent ranks were not submitted for isotherm 

analysis. Of the 17 samples collected by GRCDD personnel, 

14 isotherms were determined.

In addition to the seventeen coal mentioned above, seven 

samples were obtained from drill holes by the Semirara Mining 

Corporation (SMC) in the Panian and Himalian coalfields, also 

for high-pressure adsorption isotherm analysis. These samples, 

which were collected in conjunction with the SMC staff in 

Semirara Island, have the apparent rank of subbituminous C 

coal; analytical results were reported earlier by Flores and others (2005) and are averaged for the present report (see below).

Discussion of Results

Results of the coal quality and high-pressure methane 

adsorption isotherm analyses of coal samples are described 

in the Appendix; coal rank and adsorption isotherm data are 

listed in table 1.

Coal Quality

Coal quality and chemistry (tables 2, 3) were determined 

from analyses of moisture content; proximate and ultimate 

analyses; forms of sulfur; heat value (Btu); free swelling 

index; moist, mineral-matter free Btu; dry, mineral-matter-free 

fixed carbon; apparent rank (following ASTM classification); 

apparent specific gravity; and random vitrinite reflectance 

(Ro). Analyses performed in conjunction with the adsorption 

isotherm included equilibrium moisture, ash yield, heat value 

(Btu), moist, mineral-matter-free Btu, dry mineral-matter-free 

fixed Btu, and apparent rank. Both the moist, mineral-matterfree Btu and dry mineral-matter-free fixed carbon were determined to estimate apparent rank of the coal. That is, above 

69 (see fig. 9) on a dry mineral-matter-free fixed carbon, the 

apparent rank of the coal is estimated to be from high volatile 

A bituminous to meta-anthracite, whereas below 69 the apparent rank is estimated to range from lignite to high volatile B 

bituminous on moist, mineral-matter-free Btu. 

The USGS judged the apparent rank of the coal samples 

to be higher than those estimated by the GRCDD; rank 

classifications by both GRCDD and USGS are shown in 

figure 1. The rank of coal samples from Samar-Leyte coal 

district was estimated by the USGS as lignite A, Batan Island 

coal district as high volatile C (hvC) bituminous, Cebu coal 

district as hvC-high volatile B (hvB) bituminous, and Zamboanga Sibuguey (Malangas coalfield) as semi-anthracite. 

The coal sample from the Isabella-Cagayan coal district is of 

lower rank, ranging from lignite A to lignite B based on the 

USGS estimate. 

Figure 3. Photograph of a dipping coal-bed outcrop in Catanduanes coal district. Hammer 

handle is about 30.5 cm long. From del Rosario and Pastor (2005a).

Discussion of Results 
Figure 4. Photograph of an inclined shaft of an active underground mine in the Cebu coal district. 

From Pendon and Tilos (2005).

Figure 5. Photograph showing trenching at an outcrop 

in Catanduanes coal district for collecting coal samples. 

From del Rosario and Pastor (2005a).

 Philippines Coalbed Methane Assessment
Figure 6. Photograph illustrating the preparation of a coal sample, 

immediately following collection, for shipment to laboratory. 

Preparation consisted of double bagging the coal sample, putting 

wet tissue in the plastic bags, and wrapping for shipment. From del 

Rosario and Pastor (2005b). 

Figure 7. Photograph of drilling rig used by Semirara Mining Corporation to core coal in the Panian 

coalfield in the Semirara coal district. From Flores and others (2005).

Discussion of Results   
Figure 8. Coal core recovery from the Panian coalfield in the Semirara coal district. 

Adopted from Flores and others (2005).

In general, the equilibrium moisture of the coal samples 

appears to have been successfully retained during sample 

collection and shipment. Considering that they were collected 

from outcrops and coal mine shafts, the equilibrium moisture 

from the lignite samples, which ranges from 28.31 to 52.96 

percent for the Cotabato and Cagayan-Isabella coal districts, 

respectively, appears normal for lignite rank (see table 2). 

However, equilibrium moisture of the lignite sample from 

Catanduanes, which is 7.06 percent, is anomalous. The 

equilibrium moisture of the high rank coal samples from the 

bituminous Cebu coal district (Danao 1, Argao 1, Toledo 1, 

Dalaguete 1) and the semi-anthracite Zamboanga (Malangas 

coalfield) coal district appears to be normal.

Ash yields of the lignite coal samples are generally low, 

ranging from 2.03 to 6.55 percent (lignite B through A) except 

for the Catanduanes A coal sample, which contains 77.38 

percent (table 2). A few of the high rank coal samples, such 

as the semi-anthracite Malangas coal (M-LA), contains 36.47 

percent ash yield and the mvB bituminous Catanduanes coal 

(Catanduanes 1) contains 17.82 percent ash yield (table 2).

Four coal samples were tested for free-swelling properties, which may indicate the coking characteristic of the coal 

when burned as a fuel (ASTM, 1998) (table 3). Also, the test 

can be used to indicate the degree of oxidation of the coal. 

The free-swelling index ranges from 1.5 to 8 for three of the 

bituminous (hvBb-hvAb) coal samples (Argao 1, Toledo 1, 

Dalaguete 1) from Cebu coal district (table 3). The bituminous 

(mvB) coal sample from the Catanduanes coal district exhibits a free-swelling index of 9, as determined from full-scale 

standard profiles (ASTM, 1998).

Adsorption Isotherm 

Adsorption isotherm is defined by Mavor and Nelson 

(1977) as the quantitative relation, at constant temperature, 

that describes how the concentration of adsorbed phase molecules at an interfacial surface varies as a function of increasing 

system pressure. This relation is a measure of the sorbed gas 

storage capacity of the coal as a function of pressure (sorption 

isotherm). The most common model used to relate methane 

storage capacity to organic content of coal is the Langmuir 

isotherm. The ash yield and moisture content, which make up 

the inorganic content determined by the proximate analysis, 

influence the storage capacity of the coal. For example, the 

higher the ash yield and moisture content the lower the sorbed 

gas storage capacity of the coal. 

The results of methane adsorption isotherm analyses of 

15 coal samples from the Philippine coal districts arranged in 

alphabetical order are summarized in table 1 and described 

in detail in the Appendix. The relation between apparent 

rank, using dry, mineral-matter-free fixed carbon and moist 

mineral-matter-free Btu and the storage capacity of adsorbed 

methane in standard cubic feet per short ton (scf/t) on an 

as-received basis of 9 of these coal samples is summarized in 

figure 9; only 7 representative coal samples were plotted from 

each different apparent rank. The plot of storage capacity of 

adsorbed methane for the coal samples may be defined by an 

average curve, which increases with coal rank from lignite 

to semi-anthracite (fig. 9). Average storage capacities, on an 

as-received basis (1) range from 7.14 standard cubic meters 

per metric tonne (scm/mt) (243.1 scf/t) for the lignite in the 

   Philippines Coalbed Methane Assessment
Table 1. Summary of apparent rank and Langmuir parameters of Philippine coal 

samples. N.D., did not determine high-pressure methane adsorption. 

Langmuir isotherm 

Philippine parameters

coal districts Sample name1 Apparent rank2

Volume3 Pressure4

Batan Island BTN-01 High volatile C bituminous 10.05(342.0) 8.52(1235.7) 

Cagayan-Isabella Cagayan Valley 1 Lignite B 7.14(243.1) 4.51(653.6) 

Catanduanes Catanduanes 1 Medium volatile bituminous 30.12(1025.0) 4.50(653.1) 

Catanduanes Catanduanes A Lignite B 1.01(34.4) 12.09(1753.6) 

Cebu Danao 1 High volatile C bituminous N.D. N.D 

Cebu Argao 1 High volatile B bituminous 21.4(728.0) 6.05(877.9) 

Cebu Toledo 1 High volatile A bituminous 18.92(644.0) 4.53(656.9) 

Cebu Dalaguete 1 High volatile B bituminous 16.19(550.8) 5.32(771.2) 

Cagayan-Isabella Isabella 1 Lignite B 1.94(65.9) 7.38(1070.2) 

Cagayan-Isabella Isabella 2 Lignite B N.D. N.D. 

Negros Calatrava 1 Subbituminous B 1.19(40.5) 3.74(541.8) 

Samar Hinabangan 1 Lignite A 6.76(230.1) 16.20(2350.1) 

Samar Hinabangan 2 Lignite A N.D. N.D. 

Cotabato South Cotabato 1 Lignite A 4.50(153.2) 5.71(827.8) 

Surigao Sicahoy Bislig 1 Subbituminous B 5.36(182.3) 4.67(676.9) 

Zamboanga Sibuguey M-LC Semianthracite 22.96(781.2) 5.53(802.3) 

Zamboanga Sibuguey M-LA Semianthracite 12.90(438.9) 6.89(999.4) 

Semirara Panian and Himalian Subbituminous C 5.17(175.76) 8.66(1256.2) 

1

 Sample name as submitted by Energy Resource Development Board. 

2

 Calculated using American Society for Testing and Materials, 1998 Annual Book of 

ASTM Standards Chapter D 388-98. 

3

 Langmuir Volume is in Standard cubic meters per metric tonne, number in parentheses 

is volume in standard cubic feet per short ton. 

4

 Langmuir Pressures in megapascal per square centimeter, number in parentheses is 

pressure in pounds per square inch absolute. 

Discussion of Results 
Air dry Residual Total Equilibrium Ash yield Volatile matter Fixed carbon Hydrogen Carbon Nitrog

BTN 1 3.86 3.57 7.29 6.06 13.76 42.92 36.03 5.52 60.24 1.12 Cagayan Valley 1 50.49 7.94 54.42 48.99 5.52 22.63 17.43 2.16 27.30 0.47 Catanduanes 1 2.77 0.66 3.41 2.23 17.82 20.34 58.43 3.92 69.18 1.39 Catanduanes A 6.27 1.95 8.10 7.06 77.38 13.47 1.05 1.18 2.56 0.01 Danao 1 7.39 3.76 10.87 11.03 3.85 42.38 42.90 4.83 66.13 1.41 Argao 1 2.40 1.00 3.38 3.71 3.78 45.30 47.54 5.20 75.13 1.64 Toledo 1 2.11 0.26 2.36 1.81 7.30 42.53 47.81 4.97 74.75 1.63 Dalaguete 1 3.66 2.16 5.74 5.64 2.63 42.83 48.80 5.09 73.19 1.66 Isabella 1 56.77 7.24 59.90 27.07 2.03 21.07 17.00 2.07 26.49 0.43 Isabella 2 55.95 7.60 59.30 52.96 3.42 20.79 16.49 2.03 25.29 0.38 Calatrava 1 16.11 4.90 20.22 20.33 12.24 31.47 36.07 3.63 50.24 1.43 Hinabangan 1 34.48 4.83 37.64 37.02 6.55 30.59 25.22 3.52 38.22 0.61 Hinabangan 2 31.38 6.07 35.55 35.13 5.00 30.96 28.49 3.22 41.18 0.55 South Cotabato 1 43.40 5.90 46.74 28.31 3.58 27.35 22.33 2.79 35.66 0.42 Sicahoy Bislig 1 16.30 4.61 20.16 20.73 6.40 35.51 37.93 4.02 55.16 1.15 M-LC 3.83 0.70 4.50 2.09 5.20 12.14 78.16 3.67 82.87 2.38 M-LA 5.81 2.02 7.71 5.33 36.47 9.91 45.91 2.60 48.98 1.22 

32

Moisture (percent) Proximate analysis (percent) Ultimate analys

Table 2. Coal chemistry (moisture and proximate and ultimate analyses) for samples utilized in construction of the 

curve (see figure 9).

Sample name
Sulfate Pyritic Org

BTN 1 10,591 0.0 12,446 46.32 hvCb 1.35 0.01 0.07 0Cagayan Valley 1 4,805 0.0 5,067 44.42 lignite B 1.57 0.02 1.30 0Catanduanes 1 12,002 9.0 14,883 75.72 mvb 1.48 0.00 0.03 0Catanduanes A 294 0.0 1,777 12.56 lignite B 2.55 0.02 0.03 0Danao 1 11,586 0.0 12,100 44.83 hvCb 1.39Argao 1 13,403 3.0 13,987 49.62 hvBb 1.33Toledo 1 13,577 8.0 14,869 52.47 hvAb 1.34Dalaguete 1 12,914 1.5 13,302 50.28 hvBb 1.35Isabella 1 4,505 0.0 4,600 44.90 lignite B 1.49 0.00 0.06 0Isabella 2 4,291 0.0 4,451 44.60 lignite B 1.56 0.00 0.01 0Calatrava 1 8,811 0.0 10,156 54.30 sub B 1.53 0.01 0.10 0Hinabangan 1 6,868 0.0 7,381 45.79 lignite A 1.49 0.01 0.04 0Hinabangan 2 7,209 0.0 7,593 48.89 lignite A 1.53 0.21 0.38 2South Cotabato 1 6,123 0.0 6,364 45.28 lignite A 1.48 0.00 0.02 0Sicahoy Bislig 1 9,633 0.0 10,352 52.09 sub B 1.46 0.01 0.03 0M-LC 13,785 0.0 14,629 87.23 semianthracite 1.39 0.01 0.28 0M-LA 8,089 0.0 13,376 87.28 semianthracite 1.75 0.02 0.40 0

33

3 ASTM Chapter D 388-98; subB = Subbituminous B coal, hvCb= High volatile C bituminous coal,1 Value is in British thermal units (Btu).2 American Society for Testing and Materials (ASTM), 1998 Annual Book of ASTM Standards Chapter D 720-91

 hvBb = High volatile B bitumions coal, hvAb = High volatile A bituminous coal, mvb = Medium volatile bituminous coal

4 Random vitrinite reflectance in oil (percent).

Apparent

specific

gravity

(grams per 

cubic

centimeter)

 Forms of sulfur (perce

Apparent rank 

(ASTM)3

Calorific

value1

(moist,

mineralmatterfree

basis)

Fixed

carbon

(dry,

mineralmatterfree

basis)

Calorific

value1

Free

swelling

index2

Sample number

Table 3. Coal chemistry (calorific value, free swelling index, apparent rank and specific gravity, forms of vitrinite reflectance) for samples utilized in construction of the Philippine isotherm curve (see figure 9).
Cagayan-Isabella coal district to 30.12 scm/mt (1,025.0 scf/t) 

for the medium volatile bituminous in the Catanduanes coal 

district coal (table 1); (2) are as much as 22.96 scm/t (781.2 

scf/t) for semi-anthracite coal from the Zamboanga coal district (Malangas coalfield; M-LC); and (3) range from 16.19 to 

21.40 scm/mt (550.8 to 728 scf/t) for bituminous (hvB through 

A) coal samples from the Cebu coal district (table 1).

Thus, the ability of the Philippine coal to store methane 

is a function of rank – that is, the storage capacity drops off 

considerably with decreasing rank. The plot/curve in figure 9 

shows that lignite and subbituminous coal have similar methane storage capacities, which are from 100 to 200 scf/t; these 

are higher than storage capacity of adsorbed methane for lignite 

in North Dakota, USA, which ranges from 1.0 to 5.4 scm/mt 

(31 to 173 scf/t). This high gas storage capacity of adsorbed 

methane for Philippine lignite is an important consideration 

when evaluating the potential gas content of this coal. 

Gas content of the lignite of Samar and Cagayan coal 

districts, which have a storage capacity of adsorbed methane 

ranging from 6.76 to 7.14 scm/mt (230.1 to 243.1 scf/t) on an 

as-received basis, may be best compared to the subbituminous 

C coal of the Semirara coal district, which has storage capacity 

of adsorbed methane from 4.5 to 6.3 scm/mt (145.1 to 202.2 

scf/t) (Flores and others, 2005). The average total gas content of the subbituminous C coal in the Semirara coal district 

reported by Flores and others (2005) was measured from 

28 canisters, which ranges from 0.26 to 1.42 scm/mt (0.01 

to 45.61 scf/t). Thus, the Samar and Cagayan lignite, which 

record a higher storage capacity of adsorbed methane than the 

Semirara subbituminous coal, potentially contain more gas 

volume than the Semirara coal. 

Flores and others (2005) reported that 28 Semirara 

coal samples cored at depths of 150 to 300 m (450 to 900 ft) 

have the same gas content (0.5-0.9 cm/mt or 15-30 scf/t) as 

the CBM-producing Paleocene Fort Union Formation coal 

reservoirs in the Powder River Basin (PRB), Wyoming, USA 

at the same depths. In addition, comparison of the adsorption 

isotherms of the subbituminous C coal in the Semirara coal 

district and PRB indicates gas storage capacity of the Semirara 

coal to be above the average storage capacity of the PRB coal 

(fig. 10).

Potential Coalbed Methane Resources

Potential CBM resources in the Philippine coal districts 

can be estimated from the volumes of coal resources and their 

gas storage capacities. For the 10 districts that were studied, 

such estimates of CBM-in-place resources were made based 

on their Langmuir isotherm parameters (table 1), apparent 

coal rank (as assigned by the USGS, fig.1), and an assumed 

gas saturation of 100 percent (the ideal gas-holding capacity). 

CBM-in-place resources were estimated for the other coal 

districts on the basis of their coal rank and by extrapolating 

from the known adsorbed methane (Langmuir isotherm) from 

the studied districts. Results of these estimates are illustrated 

in figure 11, which shows the combined totals (exclusive of 

the Bukidnon and Maguindanao districts, as explained below) 

to range from10,317 MMCM to as much as 16,416 MMCM.

Estimates from Studied Coal Districts

Estimates of CBM resources in the studied coal districts 

are summarized as follows: 

Lignite coal in the Samar-Leyte, Cotabato, and CagayanIsabella coal districts, which totals as much a 593.4 MMT 

(fig. 1), potentially stores as much as 3,620 million cubic 

meters (MMCM) of methane resources (fig. 1). Of this 

total, the Cagayan-Isabella coal district accounts for as 

much as 2,400 MMCM, and the Cotabato coal district 

accounts for 1.037 MMCM (fig. 11).

Subbituminous coal, which aggregates as much as 763.5 

MMT in Negros, Semirara (including Mindoro), and 

Surigao coal districts (fig. 1) potentially holds or stores as 

much as 4,486 MMCM of methane resources, the bulk of 

it (4,481 MMMCM) in the Semirara and Surigao districts 

(fig. 11). 

Bituminous coal deposits, which are as much as 178 

MMT in Batan Island, Catanduanes, and Cebu coal districts (fig. 1), potentially store as much as 3,685 MMCM 

of methane resources, most of it in the Cebu coal district where a tragic gas explosion occurred in a mine in 

December, 2005 (The Philippine Star, p. A-29). 

Semi-anthracite coal, which is as much as 45 MMT coal 

resources (Fig. 1), in the Zamboanga Sibuguey coal district, or most specifically in the Malangas coalfield, stores 

from 580 to 1,033 MMCM (fig. 11). This coal district has 

historically had coal mine explosions, which indicate that 

the coal contains gas (Balce and others, 2005). 

Total CBM-in-place resources, based on a storage capacity that assumes 100 percent gas saturation, for the lignite 

to semi-anthracite Philippine coal in the studied coal 

districts range from 9,763 to 12,824 MMCM (fig. 11). 

Estimates From Other Coal Districts 

Coal deposits, which were not studied in the Bukidnon, 

Davao, Maguindanao, Masbate, Quezon-Polilio. Quirino, 

Sarangani, Sorsogon, and Sultan-Kudarat coal districts, contain as much as 688.5 MMT of coal resources (fig. 1). Coal 

rank ranges from lignite B to subbituminous A; however, the 

rank for the Bukidnon and Maguindanao coal is unknown, 

so no CBM-in-place resources were estimated. The CBM-inplace resource estimates (fig. 11) based on ideal gas storage 

capacity, range from nearly 555 MMCM to a maximum of 

3,592 MMCM (fig. 11), to which should be added the amounts 

in the Bukidnon and Maguindanao districts when calculated. 

1.

2.

3.

4.

5.

12  Philippines Coalbed Methane Assessment
Figure 9. Plot of adsorbed methane versus apparent rank of Philippine coal samples. Curve (yellow) defines average storage capacity of adsorb
Figure 10. Plot of adsorption isotherms versus equilibrium pressure of coal samples in the Semirara coal district and in the Pow

River Basin (PRB), Wyoming, USA. From Flores and others, 2005.
Figure 11. The potential minimum coalbed methane in-place resources (in million cubic meters, MMCM) estimated for Philippin

districts based on ideal gas storage capacity (100 percent gas saturation) of the studied coal samples. Modified from Balce and o2005).
Recommendations for Future Study

The high storage capacity of adsorbed methane is based 

on the adsorption isotherm analyses of various rank coals in 

the Philippines that were sampled from outcrops and mine 

shafts, which may have lost some inherent bed moisture 

before being analyzed. Thus, it is recommended that future 

coal samples be collected under better controlled conditions 

such as from core holes. Coal samples should be collected in 

the coal districts that were not included in the present study 

(for example, Davao, Quezon-Polilio, Masbate, Mindoro, 

Sorsogon, Sultan-Kudarat, Sarangani, and Quirino) for more 

complete evaluation of resources. Additionally, there should 

be replicate sampling of coal from the studied districts in order 

to double-check the results. It is further recommended that all 

future coal samples be desorbed for gas content in order to 

more fully assess the Philippine CBM resources.

References Cited

ASTM, 1998: Annual Book of American Society for Testing 

and Materials Standards, Chapter D 388-98 and 720-91, 

p. 174-199. 

Balce, G.R., Flores, R.M., Stricker, G.D., Papasin, R.F., 

Pendon, R.R., Taganas, R.G., other Energy Resource 

Management Board Team Members, and San Jose, E.S., 

2005, Potential coalbed methane resources in the Philippines: GEOCON 2005, Minerals and Energy Resources for 

Philippine Progress: Geological Society of the Philippines 

Annual Conference, Dec. 7-9, 2005, Makati, Manila: CDRom, file:///Volumes/MY_DISC/papers/4a_balce_flores_

frames.html, 5 p.,

BHP Engineering, 1999, Pre-feasibility study for Isabella coal 

project; for PNOC Exploration Corporation and Cogentrix Energy, Inc.: BHP Service Companies, Makati, Metro 

Manila, 18 p. 

del Rosario, R.A., Jr., and Pastor, M.S., 2005a, Sorsogon and 

Catanduanes travel report:, Geothermal and Coal Resources 

Development Division of the Department, Energy Resources 

Development Board of Energy of the Philippines, 4 p. 

del Rosario, R.A., Jr., and Pastor, M.S., 2005b, Samar travel 

report:, Geothermal and Coal Resources Development Division of the Department, Energy Resources Development 

Board of Energy of the Philippines, 5 p.

Flores, R.M., Stricker, G.D., Baquiran, G.B., Jimenez, T.M., 

Jr., Ammugauan, J.G., Gayondata, E.A., Papsin, R.F., and 

Pendon, R.R., 2005, Predicting coalbed gas production on 

Semirara Island, Philippines, from coalbed methane paradigms in the Powder River Basin, United States: GEOCON 

2005, Minerals and Energy Resources for Philippine Progress: Geological Society of the Philippines Annual

Conference, Dec. 7-9, 2005, Makati, Manila: CD-Rom, 

file:///Volumes/MY_DISC/papers/4a_flores_et al_frames.

html, 5 p. 

Mavor, M., and Nelson, C.R., 1977, Coalbed reservoir gasin-place analysis: Gas Research Institute, GRI Report No. 

GRI-97/0263, 108 p. 

Papasin, R.F., and Pendon, R.R., 2005, Travel report on the 

field validation of Daguma Agro-Minerals, Inc., drilling 

accomplishments and verification of coal occurrence in 

Barangay Kalibuhan, Palimbag, and Sultan Kudarat: Geothermal and Coal Resources Development Division, Energy 

Resources Development Board of the Department of Energy 

of the Philippines, 4 p.

Pendon, R.R., and Tilos, E.N., 2005, Travel report on the 

quarterly monitoring of Coal Operating Contract — Exploration and coal bed methane sampling in Cebu Province and 

Negros occidental: Geothermal and Coal Resources Development Division, Energy Resources Development Board of 

the Department of Energy of the Philippines, 6 p.

16  Philippines Coalbed Methane Assessment

Manuscript approved for publication March 3, 2006

Published in the Central Region, Denver, Colorado

Edited by W.R. Keefer

Graphics by Carol Olson and Jonah Sullivan

Photocomposition and design by Mari L. Kauffmann

(Contractor, ATA Services)
Appendix

The following reports on high-pressure methane adsorption, consisting of figures and 

tables of data, are taken verbatim from R.M.B. Earth Science Consultants Ltd., Delta, 

British Columbia, Canada, and have not been edited or reviewed for conformity with U.S. 

Geological Survey standards or nomenclature. The analyzed samples were supplied by 

the authors. 

A1
High Pressure Methane Adsorption

Analyses

BTN-01, Cagayan Valley 1, 

Catanduanes 1, Catanduanes A,

Argao 1, Toledo 1,

Dalaguete 1, Isabella 1,

Calatrava 1, Hinabancan 1,

South Cotabato 1, Sicahoy Bislig 1,

 M-LC, and M-LA

Analyses carried out by R.M.B. Earth Science Consultants Ltd. 

327 Rosehill Wynd, Delta British Columbia, V4M 3L8 

A2
INTRODUCTION

Fourteen coal samples were submitted for methane isotherm analyses by Dr. Romeo

Flores. 

The samples were designated: BTN-01, Cagayan Valley 1, Catanduanes 1,

Catanduanes A, Argao 1, Toledo 1, Dalaguete 1, Isabella 1, Calatrava 1, Hinabancan 1,

South Cotabato 1, Sicahoy Bislig 1, M-LC, and M-LA. This report describes the methods

and provides the analytical results.

METHODS 

The samples were received wet/damp. They were ground to -60 mesh and placed in an 

equilibrium moisture bath for a period of 20 days to confirm equilibrium moisture. A two 

gram split of each sample was used for duplicate moisture and ash analyses. A detailed 

description and overview of the adsorption measurement procedures are provided at the 

end of the Appendix. 

Results 

Adsorption Analysis 

The adsorption analysis of the sample is summarized on the attached pages in both SI 

(International System of measurement; e.g. gram and centimeter) and Imperial (Imp.) 

(British Imperial System; e.g. pound and foot) units. 

Note that Standard Temperature and Pressure (STP) in SI units is at 0°C. In

Imperial units standard (oil industry convention) STP is at a temperature of 60°F. 

Reported pressures are absolute.

A3
 (MPa) As 

Received 

Moisture 

free ash 

incl. 

ash free 

moisture 

incl 

Dry Ash 

Free 

0.15 0.17 0.16 0.18 

0.40 0.44 0.42 0.47 

0.86 0.94 0.91 1.00 

1.14 1.24 1.20 1.32 

1.47 1.61 1.55 1.71 

1.87 2.05 1.98 2.18 

2.29 2.51 2.42 2.67 

2.81 3.08 2.97 3.27 

3.40 3.72 3.59 3.95 

3.93 4.30 4.15 4.56 

4.46 4.88 4.70 5.18 

4.96 5.43 5.24 5.77 

5.32 5.83 5.62 6.19 

As 

Received 

Moisture 

free ash 

incl. 

Ash free 

moisture 

incl 

Dry Ash 

Free 

Vol. (cc/g) 10.05 11.01 10.61 11.69

 Pressure (MPa) 8.52 8.52 8.52 8.52 

SUMMARY OF ADSORPTION ANALYSES SI UNITS 

Isotherm Temperature: 28.0 oC 

Goodness of fit of Langmuir regression: 0.96 

% Ash = 5.30 % Moisture = 8.68 Density (g/cc) = 1.312 

2.279 

0.862 

1.035 

1.419 

1.809

 Pressure Adsorbed gas (cc/g) 

0.154 

0.372 

8.590 

10.290 

Langmuir Parameters 

3.126 

4.097 

5.431 

6.500 

BTN-O1 

0.0 

2.8 

5.6 

8.5 

0.0 2.0 4.0 6.0 8.0 10.0 

Sample Cell Equilibrium Pressure (MPa) 

Methane Adsorbed (cc/g)

Dry ash free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A4
 (PSIA) As 

Received 

moisture 

free ash 

incl. 

ash free 

moisture 

incl. 

Dry Ash 

Free 

5.2 5.7 5.5 6.1 

13.6 14.9 14.4 15.9 

29.3 32.0 30.9 34.0 

38.6 42.3 40.8 44.9 

50.1 54.8 52.9 58.2 

63.7 69.8 67.3 74.1 

78.1 85.5 82.5 90.8 

95.8 104.9 101.1 111.4 

115.6 126.6 122.1 134.4 

133.6 146.3 141.1 155.3 

151.6 166.0 160.1 176.2 

168.8 184.9 178.3 196.3 

181.1 198.4 191.3 210.6 

As 

Received 

Moisture 

free ash 

incl 

Ash free 

moisture 

incl 

Dry Ash 

Free

 Vol. (ft3

 /ton) 342.0 374.5 361.1 397.6 

Pressure (PSIA) 1235.7 1235.7 1235.7 1235.7 

SUMMARY OF ADSORPTION ANALYSES IMP. UNITS 

Isotherm Temperature: 82.4 oF 

Goodness of fit of Langmuir regression: 0.96 

% Ash = 5.30 % Moisture = 8.68 Density (g/cc) = 1.312 

Langmuir Parameters 

Pressure Adsorbed gas (ft3

 /ton) 

788 

943 

1246 

1493 

262 

331 

22 

453 

594 

54 

125 

150 

206 

BTN-O1 

0 

50 

100 

150 

200 

250 

300 

0 500 1000 1500 

Sample Cell Equilibrium Pressure (PSIA) 

Methane Adsorbed (SCF/t) 

Dry Ash Free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A5
A6

Pressure/Volume (MPa*g/cc)

Adsorption Langmuir Plot 

Batan Island

Sample BTN-01 

1.8 1.6 1.4 1.2 

R2 = 0.9623 

0.0 2.0 4.0 6.0 8.0 10.0 

Pressure (MPa) 

Dry ash fre

1.0 0.8 0.6 0.4 0.2 0.0 
 (MPa) As 

Received 

Moisture 

free ash 

incl. 

ash free 

moisture 

incl 

Dry Ash 

Free 

0.27 0.44 0.29 0.48 

0.58 0.93 0.61 1.02 

0.88 1.42 0.93 1.55 

1.16 1.87 1.23 2.04 

1.61 2.58 1.70 2.82 

2.07 3.32 2.18 3.63 

2.68 4.30 2.83 4.71 

3.26 5.24 3.45 5.73 

3.70 5.94 3.91 6.49 

4.12 6.61 4.35 7.23 

4.50 7.22 4.75 7.89 

4.73 7.59 5.00 8.30 

4.88 7.82 5.15 8.56 

As 

Received 

Moisture 

free ash 

incl. 

Ash free 

moisture 

incl 

Dry Ash 

Free 

Vol. (cc/g) 7.14 11.46 7.55 12.54

 Pressure (MPa) 4.51 4.51 4.51 4.51 

SUMMARY OF ADSORPTION ANALYSES SI UNITS 

Isotherm Temperature: 28.0 oC 

Goodness of fit of Langmuir regression: 1.00 

% Ash = 5.34 % Moisture = 37.67 Density (g/cc) = 1.100

 Pressure Adsorbed gas (cc/g) 

0.186 

0.400 

0.642 

0.879 

1.333 

1.829 

2.689 

3.640 

4.648 

6.022 

Langmuir Parameters 

7.464 

8.936 

10.174 

Cagayan Valley 1 

0.0 

2.5 

5.0 

7.5 

10.0 

12.5 

0.0 2.0 4.0 6.0 8.0 10.0 12.0 

Sample Cell Equilibrium Pressure (MPa) 

Methane Adsorbed (cc/g)

Dry ash free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A7
 (MPa) As 

Received 

Moisture 

free ash 

incl. 

ash free 

moisture 

incl 

Dry Ash 

Free 

0.27 0.44 0.29 0.48 

0.58 0.93 0.61 1.02 

0.88 1.42 0.93 1.55 

1.16 1.87 1.23 2.04 

1.61 2.58 1.70 2.82 

2.07 3.32 2.18 3.63 

2.68 4.30 2.83 4.71 

3.26 5.24 3.45 5.73 

3.70 5.94 3.91 6.49 

4.12 6.61 4.35 7.23 

4.50 7.22 4.75 7.89 

4.73 7.59 5.00 8.30 

4.88 7.82 5.15 8.56 

As 

Received 

Moisture 

free ash 

incl. 

Ash free 

moisture 

incl 

Dry Ash 

Free 

Vol. (cc/g) 7.14 11.46 7.55 12.54

 Pressure (MPa) 4.51 4.51 4.51 4.51 

SUMMARY OF ADSORPTION ANALYSES SI UNITS 

Isotherm Temperature: 28.0 oC 

Goodness of fit of Langmuir regression: 1.00 

% Ash = 5.34 % Moisture = 37.67 Density (g/cc) = 1.100

 Pressure Adsorbed gas (cc/g) 

0.186 

0.400 

0.642 

0.879 

1.333 

1.829 

2.689 

3.640 

4.648 

6.022 

Langmuir Parameters 

7.464 

8.936 

10.174 

Cagayan Valley 1 

0.0 

2.5 

5.0 

7.5 

10.0 

12.5 

0.0 2.0 4.0 6.0 8.0 10.0 12.0 

Sample Cell Equilibrium Pressure (MPa) 

Methane Adsorbed (cc/g)

Dry ash free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A8
Adsorption Langmuir Plot

Cagayan-Isabella

Sample Cagayan Valley 1

0.0 2.0 4.0 6.0 8.0 10.0 

Pressure (MPa) 

A9 

R2 = 0.9988 

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 

Pressure/Volume (MPa*g/cc) Dry ash fr
 (MPa) As 

Received 

Moisture 

free ash 

incl. 

ash free 

moisture 

incl 

Dry Ash 

Free 

1.84 1.90 2.19 2.26 

3.77 3.88 4.47 4.63 

5.94 6.11 7.05 7.30 

7.95 8.18 9.44 9.77 

9.68 9.97 11.50 11.90 

11.03 11.35 13.10 13.55 

12.44 12.80 14.77 15.29 

13.78 14.18 16.36 16.93 

15.53 15.98 18.44 19.08 

17.77 18.28 21.10 21.83 

19.14 19.70 22.73 23.52 

19.87 20.45 23.60 24.42 

21.01 21.63 24.95 25.82 

As 

Received 

Moisture 

free ash 

incl. 

Ash free 

moisture 

incl 

Dry Ash 

Free 

Vol. (cc/g) 30.12 31.00 35.77 37.01

 Pressure (MPa) 4.50 4.50 4.50 4.50 

SUMMARY OF ADSORPTION ANALYSES SI UNITS 

Isotherm Temperature: 28.0 oC 

Goodness of fit of Langmuir regression: 0.98 

% Ash = 15.79 % Moisture = 2.83 Density (g/cc) = 1.421 

Langmuir Parameters 

7.786 

8.872 

10.212 

3.189 

3.924 

5.118 

6.447 

0.988 

1.463 

1.983 

2.533

 Pressure Adsorbed gas (cc/g) 

0.370 

0.605 

Catanduanes 1 

0.0 

5.0 

10.0 

15.0 

20.0 

25.0 

30.0 

35.0 

0.0 2.0 4.0 6.0 8.0 10.0 12.0 

Sample Cell Equilibrium Pressure (MPa) 

Methane Adsorbed (cc/g)

Dry ash free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A10
 (PSIA) As 

Received 

moisture 

free ash 

incl. 

ash free 

moisture 

incl. 

Dry Ash 

Free 

62.7 64.5 74.4 77.0 

128.2 131.9 152.2 157.5 

202.1 208.0 240.0 248.3 

270.6 278.5 321.3 332.5 

329.5 339.1 391.3 404.9 

375.3 386.2 445.6 461.1 

423.3 435.7 502.7 520.2 

468.9 482.5 556.8 576.1 

528.4 543.8 627.5 649.3 

604.5 622.1 717.8 742.8 

651.2 670.2 773.3 800.2 

676.2 695.8 802.9 830.8 

715.0 735.8 849.1 878.6 

As 

Received 

Moisture 

free ash 

incl 

Ash free 

moisture 

incl 

Dry Ash 

Free

 Vol. (ft3

 /ton) 1025.0 1054.8 1217.2 1259.4 

Pressure (PSIA) 653.1 653.1 653.1 653.1 

SUMMARY OF ADSORPTION ANALYSES IMP. UNITS 

Isotherm Temperature: 82.4 oF 

Goodness of fit of Langmuir regression: 0.98 

% Ash = 15.79 % Moisture= 2.83 Density (g/cc) = 1.421 

Langmuir Parameters 

1129 

1287 

1481 

462 

569 

742 

935 

143 

212 

288 

367 

Pressure Adsorbed gas (ft3

 /ton) 

54 

88 

Catanduanes 1 

0 

200 

400 

600 

800 

1000 

1200 

0 500 1000 1500 

Sample Cell Equilibrium Pressure (PSIA) 

Methane Adsorbed (SCF/t)

Dry Ash Free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A11
Adsorption Langmuir Plot

Catanduanes

Sample Catanduanes 1

0.0 2.0 4.0 6.0 8.0 10.0 

Pressure (MPa) 

A12 

R2 = 0.9841 

0.0 0.1 0.1 0.2 0.2 0.3 0.3 0.4 0.4 0.5 

Pressure/Volume (MPa*g/cc) Dry ash free 
 (MPa) As 

Received 

Moisture 

free ash 

incl. 

ash free 

moisture 

incl 

Dry Ash 

Free 

0.03 0.04 0.15 0.22 

0.06 0.06 0.24 0.38 

0.11 0.11 0.46 0.71 

0.12 0.13 0.53 0.82 

0.13 0.15 0.58 0.90 

0.18 0.20 0.79 1.22 

0.25 0.27 1.10 1.70 

0.28 0.30 1.20 1.86 

0.39 0.42 1.69 2.62 

0.41 0.45 1.79 2.77 

0.44 0.48 1.92 2.97 

As 

Received 

Moisture 

free ash 

incl. 

Ash free 

moisture 

incl 

Dry Ash 

Free 

Vol. (cc/g) 1.01 1.10 4.39 6.80

 Pressure (MPa) 12.09 12.09 12.09 12.09 

SUMMARY OF ADSORPTION ANALYSES SI UNITS 

Isotherm Temperature: 28.0 oC 

Goodness of fit of Langmuir regression: 0.84 

% Ash = 76.99 % Moisture = 8.17 Density (g/cc) = 2.237 

Langmuir Parameters 

9.550 

3.824 

5.184 

6.592 

8.034 

1.228 

1.714 

2.203 

2.694

 Pressure Adsorbed gas (cc/g) 

0.351 

0.762 

Catanduanes A 

0.0 

1.0 

2.0 

0.0 2.0 4.0 6.0 8.0 10.0 

Sample Cell Equilibrium Pressure (MPa) 

Methane Adsorbed (cc/g)

Dry ash free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A13
 (PSIA) As 

Received 

moisture 

free ash 

incl. 

ash free 

moisture 

incl. 

Dry Ash 

Free 

1.1 1.2 4.9 7.7 

1.9 2.1 8.2 12.8 

3.6 3.9 15.5 24.1 

4.1 4.5 17.9 27.8 

4.6 5.0 19.9 30.8 

6.2 6.7 26.8 41.5 

8.6 9.3 37.3 57.8 

9.4 10.2 40.8 63.2 

13.3 14.4 57.6 89.3 

14.0 15.2 60.8 94.2 

15.0 16.3 65.2 101.0 

As 

Received 

Moisture 

free ash 

incl 

Ash free 

moisture 

incl 

Dry Ash 

Free

 Vol. (ft3

 /ton) 34.4 37.4 149.3 231.5 

Pressure (PSIA) 1753.6 1753.6 1753.6 1753.6 

SUMMARY OF ADSORPTION ANALYSES IMP. UNITS 

Isotherm Temperature: 82.4 oF 

Goodness of fit of Langmuir regression: 0.84 

% Ash = 76.99 % Moisture = 8.17 Density (g/cc) = 2.237 

Langmuir Parameters 

1385 

555 

752 

956 

1165 

178 

249 

320 

391 

Pressure Adsorbed gas (ft3

 /ton) 

51 

110 

Catanduanes A 

0 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

0 200 400 600 800 1000 1200 1400 

Sample Cell Equilibrium Pressure (PSIA) 

Methane Adsorbed (

SCF/t) 

Dry Ash Free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A14
A15

Pressure/Volume (MPa*g/cc)

Adsorption Langmuir Plot

Catanduanes

Sample Catanduanes A

3.5 3.0 2.5 

R2 = 0.8433 

0.0 0.5 1.0 1.5 

0.0 2.0 4.0 6.0 8.0 10.0 

Pressure (MPa) 

Dry ash free 

2.0 
 (MPa) As 

Received 

Moisture 

free ash 

incl. 

ash free 

moisture 

incl 

Dry Ash 

Free 

0.25 0.26 0.27 0.28 

0.98 1.02 1.02 1.07 

1.76 1.84 1.85 1.93 

2.52 2.63 2.63 2.76 

3.71 3.88 3.88 4.07 

5.04 5.26 5.27 5.52 

6.64 6.94 6.96 7.29 

8.06 8.42 8.44 8.84 

9.59 10.02 10.05 10.52 

10.82 11.30 11.33 11.86 

12.02 12.57 12.59 13.19 

12.71 13.29 13.32 13.94 

13.63 14.25 14.28 14.95 

As 

Received 

Moisture 

free ash 

incl. 

Ash free 

moisture 

incl 

Dry Ash 

Free 

Vol. (cc/g) 21.40 22.36 22.41 23.47

 Pressure (MPa) 6.05 6.05 6.05 6.05 

SUMMARY OF ADSORPTION ANALYSES SI UNITS 

Isotherm Temperature: 28.0 oC 

Goodness of fit of Langmuir regression: 0.98 

% Ash = 4.52 % Moisture = 4.31 Density (g/cc) = 1.308 

Langmuir Parameters 

7.785 

8.940 

10.942 

2.521 

3.502 

4.946 

6.338 

0.536 

0.791 

1.215 

1.644

 Pressure Adsorbed gas (cc/g) 

0.092 

0.283 

Argao 1 

0.0 

5.9 

11.8 

17.8 

23.7 

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 

Sample Cell Equilibrium Pressure (MPa) 

Methane Adsorbed (cc/g)

Dry ash free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A16
 (PSIA) As 

Received 

moisture 

free ash 

incl. 

ash free 

moisture 

incl. 

Dry Ash 

Free 

8.6 9.0 9.0 9.4 

33.2 34.7 34.8 36.4 

60.0 62.7 62.8 65.8 

85.6 89.4 89.6 93.9 

126.2 131.9 132.2 138.4 

171.4 179.1 179.5 188.0 

226.1 236.3 236.8 248.0 

274.2 286.6 287.2 300.8 

326.4 341.1 341.9 358.0 

368.0 384.6 385.4 403.6 

409.1 427.6 428.5 448.8 

432.6 452.1 453.1 474.5 

463.9 484.8 485.9 508.9 

As 

Received 

Moisture 

free ash 

incl 

Ash free 

moisture 

incl 

Dry Ash 

Free

 Vol. (ft3

 /ton) 728.0 760.8 762.5 798.5 

Pressure (PSIA) 877.9 877.9 877.9 877.9 

SUMMARY OF ADSORPTION ANALYSES IMP. UNITS 

Isotherm Temperature: 82.4 oF 

Goodness of fit of Langmuir regression: 0.98 

% Ash = 4.52 % Moisture = 4.31 Density (g/cc) = 1.308 

Langmuir Parameters 

1129 

1297 

1587 

366 

508 

717 

919 

78 

115 

176 

238 

Pressure Adsorbed gas (ft3

 /ton) 

13 

41 

Argao 1 

0 

150 

300 

450 

600 

750 

0 500 1000 1500 

Sample Cell Equilibrium Pressure (PSIA) 

Methane Adsorbed (

SCF/t) 

Dry Ash Free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A17
Adsorption Langmuir Plot

Cebu

Sample Argao 1

R2 = 0.9783 

Dry ash f

0.0 2.0 4.0 6.0 8.0 10.0 

Pressure (MPa) 

A18 

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 

Pressure/Volume (MPa*g/cc)
 (MPa) As 

Received 

Moisture 

free ash 

incl. 

ash free 

moisture 

incl 

Dry Ash 

Free 

0.47 0.49 0.51 0.52 

1.28 1.31 1.38 1.42 

2.17 2.23 2.33 2.40 

3.02 3.10 3.25 3.34 

4.13 4.25 4.45 4.58 

5.34 5.48 5.74 5.91 

6.86 7.04 7.38 7.59 

8.25 8.47 8.87 9.13 

9.42 9.68 10.14 10.43 

10.65 10.93 11.45 11.79 

11.68 12.00 12.57 12.93 

12.54 12.88 13.49 13.89 

13.28 13.64 14.29 14.70 

As 

Received 

Moisture 

free ash 

incl. 

Ash free 

moisture 

incl 

Dry Ash 

Free 

Vol. (cc/g) 18.92 19.44 20.36 20.95

 Pressure (MPa) 4.53 4.53 4.53 4.53 

SUMMARY OF ADSORPTION ANALYSES SI UNITS 

Isotherm Temperature: 28.0 oC 

Goodness of fit of Langmuir regression: 0.99 

% Ash = 7.05 % Moisture = 2.63 Density (g/cc) = 1.309

 Pressure Adsorbed gas (cc/g) 

0.138 

0.332 

0.561 

0.807 

1.194 

1.682 

2.526 

3.484 

4.525 

5.880 

Langmuir Parameters 

7.349 

8.817 

10.869 

Toledo 1 

0.0 

5.9 

11.8 

17.8 

0.0 2.0 4.0 6.0 8.0 10.0 12.0 

Sample Cell Equilibrium Pressure (MPa) 

Methane Adsorbed (cc/g)

Dry ash free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A19
 (PSIA) As 

Received 

moisture 

free ash 

incl. 

ash free 

moisture 

incl. 

Dry Ash 

Free 

16.1 16.5 17.3 17.8 

43.5 44.7 46.8 48.2 

73.7 75.7 79.3 81.6 

102.7 105.5 110.5 113.7 

140.7 144.5 151.4 155.8 

181.6 186.5 195.4 201.0 

233.4 239.7 251.1 258.4 

280.7 288.3 302.0 310.8 

320.7 329.3 345.0 355.1 

362.3 372.1 389.8 401.1 

397.5 408.2 427.7 440.1 

426.8 438.3 459.1 472.5 

451.9 464.1 486.2 500.4 

As 

Received 

Moisture 

free ash 

incl 

Ash free 

moisture 

incl 

Dry Ash 

Free

 Vol. (ft3

 /ton) 644.0 661.3 692.8 712.9 

Pressure (PSIA) 656.9 656.9 656.9 656.9 

SUMMARY OF ADSORPTION ANALYSES IMP. UNITS 

Isotherm Temperature: 82.4 oF 

Goodness of fit of Langmuir regression: 0.99 

% Ash = 7.05 % Moisture = 2.63 Density (g/cc) = 1.309 

Langmuir Parameters 

1066 

1279 

1576 

366 

505 

656 

853 

81 

117 

173 

244 

Pressure Adsorbed gas (ft3

 /ton) 

20 

48 

Toledo 1 

0 

200 

400 

600 

800 

0 500 1000 1500 

Sample Cell Equilibrium Pressure (PSIA) 

Methane Adsorbed (

SCF/t) 

Dry Ash Free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A20
Adsorption Langmuir Plot

Cebu

Sample Toledo 1

0.0 2.0 4.0 6.0 8.0 10.

Pressure (MPa) 

A21 

R2 = 0.9933 

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 

Pressure/Volume (MPa*g/cc) Dry ash 
 (MPa) As 

Received 

Moisture 

free ash 

incl. 

ash free 

moisture 

incl 

Dry Ash 

Free 

1.13 1.20 1.15 1.23 

2.02 2.16 2.07 2.21 

3.02 3.22 3.08 3.30 

4.01 4.28 4.09 4.38 

4.84 5.16 4.94 5.28 

5.51 5.89 5.63 6.02 

6.25 6.68 6.38 6.82 

7.01 7.48 7.15 7.65 

8.00 8.54 8.16 8.73 

8.83 9.44 9.02 9.64 

9.66 10.32 9.86 10.55 

10.22 10.92 10.43 11.16 

10.83 11.57 11.06 11.83 

As 

Received 

Moisture 

free ash 

incl. 

Ash free 

moisture 

incl 

Dry Ash 

Free 

Vol. (cc/g) 16.19 17.29 16.52 17.67

 Pressure (MPa) 5.32 5.32 5.32 5.32 

SUMMARY OF ADSORPTION ANALYSES SI UNITS 

Isotherm Temperature: 28.0 oC 

Goodness of fit of Langmuir regression: 0.99 

% Ash = 2.03 % Moisture = 6.37 Density (g/cc) = 1.300 

Langmuir Parameters 

7.900 

9.100 

10.840 

3.289 

4.023 

5.228 

6.591 

1.180 

1.651 

2.158 

2.668

 Pressure Adsorbed gas (cc/g) 

0.455 

0.760 

Dalaguete 1 

0.0 

2.8 

5.6 

8.5 

11.3 

14.1 

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 

Sample Cell Equilibrium Pressure (MPa) 

Methane Adsorbed (cc/g)

Dry ash free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A22
 (PSIA) As 

Received 

moisture 

free ash 

incl. 

ash free 

moisture 

incl. 

Dry Ash 

Free 

38.4 41.0 39.2 41.9 

68.9 73.6 70.3 75.2 

102.7 109.7 104.8 112.1 

136.4 145.7 139.2 148.9 

164.5 175.7 167.9 179.6 

187.5 200.3 191.4 204.7 

212.7 227.1 217.1 232.2 

238.4 254.6 243.4 260.3 

272.1 290.7 277.8 297.1 

300.6 321.0 306.8 328.2 

328.8 351.2 335.7 359.0 

347.8 371.4 355.0 379.7 

368.7 393.8 376.3 402.5 

As 

Received 

Moisture 

free ash 

incl 

Ash free 

moisture 

incl 

Dry Ash 

Free

 Vol. (ft3

 /ton) 550.8 588.3 562.2 601.3 

Pressure (PSIA) 771.2 771.2 771.2 771.2 

SUMMARY OF ADSORPTION ANALYSES IMP. UNITS 

Isotherm Temperature: 82.4 oF 

Goodness of fit of Langmuir regression: 0.99 

% Ash = 2.03 % Moisture = 6.37 Density (g/cc) = 1.300 

Langmuir Parameters 

1146 

1320 

1572 

477 

584 

758 

956 

171 

239 

313 

387 

Pressure Adsorbed gas (ft3

 /ton) 

66 

110 

Dalaguete 1 

0 

50 

100 

150 

200 

250 

300 

350 

400 

450 

500 

0 500 1000 1500 2000 

Sample Cell Equilibrium Pressure (PSIA) 

Methane Adsorbed (

SCF/t)

Dry Ash Free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A23
Adsorption Langmuir Plot

Cebu

Sample Dalaguete 1

0.0 2.0 4.0 6.0 8.0 10.0 

Pressure (MPa) 

A24 

R2 = 0.994 

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 

Pressure/Volume (MPa*g/cc) Dry ash free 
 (MPa) As 

Received 

Moisture 

free ash 

incl. 

ash free 

moisture 

incl 

Dry Ash 

Free 

0.04 0.11 0.04 0.11 

0.11 0.28 0.11 0.29 

0.19 0.49 0.20 0.51 

0.28 0.71 0.29 0.75 

0.35 0.88 0.36 0.93 

0.45 1.13 0.45 1.19 

0.60 1.52 0.61 1.60 

0.70 1.78 0.72 1.88 

0.83 2.10 0.85 2.21 

0.87 2.22 0.89 2.34 

0.97 2.46 0.99 2.60 

1.03 2.62 1.06 2.77 

1.07 2.71 1.09 2.86 

As 

Received 

Moisture 

free ash 

incl. 

Ash free 

moisture 

incl 

Dry Ash 

Free 

Vol. (cc/g) 1.94 4.90 1.98 5.17

 Pressure (MPa) 7.38 7.38 7.38 7.38 

SUMMARY OF ADSORPTION ANALYSES SI UNITS 

Isotherm Temperature: 28.0 oC 

Goodness of fit of Langmuir regression: 0.97 

% Ash = 2.07 % Moisture = 60.53 Density (g/cc) = 1.156 

Langmuir Parameters 

7.095 

8.426 

9.506 

3.174 

4.148 

5.129 

6.116 

0.845 

1.338 

1.838 

2.332

 Pressure Adsorbed gas (cc/g) 

0.148 

0.408 

Isabella 1 

0.0 

1.0 

2.0 

3.0 

4.0 

0.0 2.0 4.0 6.0 8.0 10.0 

Sample Cell Equilibrium Pressure (MPa) 

Methane Adsorbed (cc/g) 

Dry ash free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A25
 (PSIA) As 

Received 

moisture 

free ash 

incl. 

ash free 

moisture 

incl. 

Dry Ash 

Free 

1.4 3.7 1.5 3.9 

3.7 9.4 3.8 10.0 

6.5 16.5 6.7 17.5 

9.6 24.2 9.8 25.5 

11.8 30.0 12.1 31.6 

15.2 38.4 15.5 40.5 

20.4 51.6 20.8 54.4 

23.9 60.5 24.4 63.8 

28.2 71.3 28.8 75.3 

29.8 75.4 30.4 79.5 

33.0 83.7 33.7 88.3 

35.2 89.2 36.0 94.1 

36.4 92.3 37.2 97.4 

As 

Received 

Moisture 

free ash 

incl 

Ash free 

moisture 

incl 

Dry Ash 

Free

 Vol. (ft3

 /ton) 65.9 166.9 67.3 176.1 

Pressure (PSIA) 1070.2 1070.2 1070.2 1070.2 

SUMMARY OF ADSORPTION ANALYSES IMP. UNITS 

Isotherm Temperature: 82.4 oF 

Goodness of fit of Langmuir regression: 0.97 

% Ash = 2.07 % Moisture = 60.53 Density (g/cc) = 1.156 

Langmuir Parameters 

1029 

1222 

1379 

460 

602 

744 

887 

123 

194 

267 

338 

Pressure Adsorbed gas (ft3

 /ton) 

22 

59 

Isabella 1 

0 

20 

40 

60 

80 

100 

120 

140 

0 200 400 600 800 1000 1200 1400 

Sample Cell Equilibrium Pressure (PSIA) 

Methane Adsorbed (

SCF/t) 

Dry Ash Free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A26
Adsorption Langmuir Plot

Cayayan-Isabella

Sample Isabella 1

A27 

R2 = 0.9748 

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 

Pressure (MPa) 

Pressure/Volume (MPa*g/cc)

Dry ash free 
 (MPa) As 

Received 

Moisture 

free ash 

incl. 

ash free 

moisture 

incl 

Dry Ash 

Free 

0.04 0.05 0.05 0.06 

0.10 0.13 0.11 0.15 

0.18 0.22 0.20 0.26 

0.24 0.30 0.26 0.34 

0.32 0.41 0.36 0.46 

0.39 0.50 0.44 0.57 

0.49 0.62 0.54 0.71 

0.59 0.75 0.66 0.85 

0.73 0.92 0.81 1.05 

0.77 0.97 0.86 1.11 

0.81 1.02 0.89 1.16 

0.81 1.02 0.90 1.17 

As 

Received 

Moisture 

free ash 

incl. 

Ash free 

moisture 

incl 

Dry Ash 

Free 

Vol. (cc/g) 1.19 1.50 1.32 1.71

 Pressure (MPa) 3.74 3.74 3.74 3.74 

SUMMARY OF ADSORPTION ANALYSES SI UNITS 

Isotherm Temperature: 28.0 oC 

Goodness of fit of Langmuir regression: 0.99 

% Ash = 9.81 % Moisture = 20.74 Density (g/cc) = 1.592 

Langmuir Parameters 

Adsorbed gas (cc/g) 

9.002 

3.669 

4.997 

6.436 

7.900 

0.890

 Pressure 

1.316 

1.820 

2.707 

0.136 

0.407 

0.649 

Calatrava 1 

0.0 

0.5 

1.0 

1.5 

2.0 

0.0 2.0 4.0 6.0 8.0 10.0 

Sample Cell Equilibrium Pressure (MPa) 

Methane Adsorbed (cc/g) 

Dry ash free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A28
 (PSIA) As 

Received 

moisture 

free ash 

incl. 

ash free 

moisture 

incl. 

Dry Ash 

Free 

1.4 1.8 1.6 2.0 

3.5 4.4 3.8 5.0 

6.0 7.6 6.7 8.7 

8.0 10.1 8.9 11.5 

11.0 13.8 12.2 15.8 

13.4 16.9 14.8 19.2 

16.7 21.0 18.5 24.0 

20.2 25.4 22.3 29.0 

24.8 31.3 27.5 35.7 

26.3 33.2 29.1 37.8 

27.4 34.6 30.4 39.5 

27.6 34.9 30.6 39.8 

As 

Received 

Moisture 

free ash 

incl 

Ash free 

moisture 

incl 

Dry Ash 

Free

 Vol. (ft3

 /ton) 40.5 51.1 44.9 58.3 

Pressure (PSIA) 541.8 541.8 541.8 541.8 

SUMMARY OF ADSORPTION ANALYSES IMP. UNITS 

Isotherm Temperature: 82.4 oF 

Goodness of fit of Langmuir regression: 0.99 

% Ash = 9.81 % Moisture = 20.74 Density (g/cc) = 1.592 

Langmuir Parameters 

1146 

1306 

393 

532 

725 

933 

94 

129 

191 

264 

Pressure Adsorbed gas (ft3

 /ton) 

20 

59 

Calatrava 1 

0 

20 

40 

60 

0 200 400 600 800 1000 1200 1400 

Sample Cell Equilibrium Pressure (PSIA) 

Methane Adsorbed (

SCF/t) 

Dry Ash Free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A29
Adsorption Langmuir Plot

Negros

Sample Calatrava 1

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 

Pressure (MPa) 

A30 

R2 = 0.99 

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 

Pressure/Volume (MPa*g/cc) Dry ash free 
 (MPa) As 

Received 

Moisture 

free ash 

incl. 

ash free 

moisture 

incl 

Dry Ash 

Free 

0.06 0.10 0.06 0.11 

0.19 0.31 0.20 0.34 

0.33 0.55 0.35 0.60 

0.50 0.82 0.52 0.89 

0.67 1.11 0.71 1.21 

0.85 1.40 0.89 1.52 

1.09 1.80 1.15 1.96 

1.35 2.23 1.42 2.42 

1.63 2.68 1.71 2.91 

1.91 3.14 2.00 3.41 

2.11 3.48 2.22 3.77 

2.33 3.83 2.44 4.15 

2.50 4.13 2.63 4.47 

As 

Received 

Moisture 

free ash 

incl. 

Ash free 

moisture 

incl 

Dry Ash 

Free 

Vol. (cc/g) 6.76 11.14 7.10 12.08

 Pressure (MPa) 16.20 16.20 16.20 16.20 

SUMMARY OF ADSORPTION ANALYSES SI UNITS 

Isotherm Temperature: 28.0 oC 

Goodness of fit of Langmuir regression: 0.96 

% Ash = 4.71 % Moisture = 39.32 Density (g/cc) = 1.237 

Langmuir Parameters 

7.094 

8.453 

9.835 

3.190 

4.162 

5.128 

6.124 

0.853 

1.324 

1.816 

2.339

 Pressure Adsorbed gas (cc/g) 

0.152 

0.420 

Hinabangan Samar 1 

0.0 

1.0 

2.0 

3.0 

4.0 

5.0 

0.0 2.0 4.0 6.0 8.0 10.0 

Sample Cell Equilibrium Pressure (MPa) 

Methane Adsorbed (cc/g)

Dry ash free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A31
 (PSIA) As 

Received 

moisture 

free ash 

incl. 

ash free 

moisture 

incl. 

Dry Ash 

Free 

2.0 3.4 2.1 3.6 

6.4 10.6 6.8 11.5 

11.4 18.7 11.9 20.3 

17.0 28.0 17.8 30.3 

23.0 37.8 24.1 41.0 

28.9 47.7 30.4 51.7 

37.2 61.4 39.1 66.5 

46.1 75.9 48.3 82.3 

55.4 91.2 58.1 98.9 

64.8 106.9 68.1 115.9 

71.8 118.4 75.4 128.3 

79.1 130.4 83.0 141.4 

85.2 140.4 89.4 152.2 

As 

Received 

Moisture 

free ash 

incl 

Ash free 

moisture 

incl 

Dry Ash 

Free

 Vol. (ft3

 /ton) 230.1 379.1 241.4 411.0 

Pressure (PSIA) 2350.1 2350.1 2350.1 2350.1 

SUMMARY OF ADSORPTION ANALYSES IMP. UNITS 

Isotherm Temperature: 82.4 oF 

Goodness of fit of Langmuir regression: 0.96 

% Ash = 4.71 % Moisture = 39.32 Density (g/cc) = 1.237 

Langmuir Parameters 

1029 

1226 

1427 

463 

604 

744 

888 

124 

192 

263 

339 

Pressure Adsorbed gas (ft3

 /ton) 

22 

61 

Hinabangan Samar 1 

0 

25 

50 

75 

100 

125 

150 

175 

200 

0 200 400 600 800 1000 1200 1400 1600 

Sample Cell Equilibrium Pressure (PSIA) 

Methane Adsorbed (

SCF/t) 

Dry Ash Free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

Series9 

A32
A33

Pressure/Volume (MPa*g/cc)

Adsorption Langmuir Plot

Samar

Sample Hinabangan 1

2.5 2.0 1.5 

R2 = 0.962 

0.0 2.0 4.0 6.0 8.0 10.0 

Pressure (MPa) 

Dry ash f

1.0 0.5 0.0 
 (MPa) As 

Received 

Moisture 

free ash 

incl. 

ash free 

moisture 

incl 

Dry Ash 

Free 

0.27 0.45 0.29 0.50 

0.57 0.96 0.61 1.06 

0.84 1.42 0.90 1.58 

1.10 1.85 1.17 2.05 

1.30 2.18 1.38 2.42 

1.46 2.45 1.55 2.72 

1.64 2.75 1.74 3.05 

1.89 3.18 2.01 3.53 

2.23 3.75 2.37 4.16 

2.46 4.13 2.62 4.59 

2.65 4.44 2.81 4.94 

2.76 4.64 2.94 5.16 

As 

Received 

Moisture 

free ash 

incl. 

Ash free 

moisture 

incl 

Dry Ash 

Free 

Vol. (cc/g) 4.50 7.56 4.79 8.40

 Pressure (MPa) 5.71 5.71 5.71 5.71 

SUMMARY OF ADSORPTION ANALYSES SI UNITS 

Isotherm Temperature: 28.0 oC 

Goodness of fit of Langmuir regression: 0.99 

% Ash = 5.94 % Moisture = 40.45 Density (g/cc) = 1.300 

Langmuir Parameters 

8.145 

9.545 

3.373 

4.101 

5.331 

6.724 

1.275 

1.763 

2.256 

2.744

 Pressure Adsorbed gas (cc/g) 

0.407 

0.811 

South Cotabato 1 

0.0 

2.8 

5.6 

8.5 

0.0 2.0 4.0 6.0 8.0 10.0 

Sample Cell Equilibrium Pressure (MPa) 

Methane Adsorbed (cc/g) 

Dry ash free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A34
 (PSIA) As 

Received 

moisture 

free ash 

incl. 

ash free 

moisture 

incl. 

Dry Ash 

Free 

9.2 15.5 9.8 17.2 

19.4 32.6 20.6 36.2 

28.7 48.3 30.6 53.6 

37.4 62.9 39.8 69.9 

44.1 74.1 46.9 82.4 

49.6 83.3 52.7 92.5 

55.7 93.5 59.2 103.9 

64.5 108.3 68.5 120.3 

75.9 127.5 80.7 141.6 

83.8 140.7 89.1 156.3 

90.0 151.2 95.7 168.0 

94.1 158.0 100.0 175.5 

As 

Received 

Moisture 

free ash 

incl 

Ash free 

moisture 

incl 

Dry Ash 

Free

 Vol. (ft3

 /ton) 153.2 257.2 162.8 285.7 

Pressure (PSIA) 827.8 827.8 827.8 827.8 

SUMMARY OF ADSORPTION ANALYSES IMP. UNITS 

Isotherm Temperature: 82.4 oF 

Goodness of fit of Langmuir regression: 0.99 

% Ash = 5.94 % Moisture = 40.45 Density (g/cc) = 1.300 

Langmuir Parameters 

1181 

1384 

489 

595 

773 

975 

185 

256 

327 

398 

Pressure Adsorbed gas (ft3

 /ton) 

59 

118 

South Cotabato 1 

0 

50 

100 

150 

200 

250 

0 200 400 600 800 1000 1200 1400 1600 

Sample Cell Equilibrium Pressure (PSIA) 

Methane Adsorbed (

SCF/t) 

Dry Ash Free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A35
Adsorption Langmuir Plot

Cotabato

Sample South Cotabato 1

0.0 2.0 4.0 6.0 8.0 10.0 

Pressure (MPa) 

A36 

R2 = 0.9919 

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 

Pressure/Volume (MPa*g/cc) Dry ash free 
 (MPa) As 

Received 

Moisture 

free ash 

incl. 

ash free 

moisture 

incl 

Dry Ash 

Free 

0.44 0.56 0.47 0.61 

0.74 0.94 0.80 1.03 

1.12 1.41 1.19 1.54 

1.45 1.84 1.55 2.00 

1.78 2.26 1.91 2.46 

2.05 2.60 2.19 2.83 

2.32 2.94 2.48 3.20 

2.55 3.23 2.72 3.51 

2.87 3.64 3.06 3.96 

3.18 4.03 3.40 4.38 

3.33 4.22 3.55 4.59 

3.51 4.45 3.75 4.85 

As 

Received 

Moisture 

free ash 

incl. 

Ash free 

moisture 

incl 

Dry Ash 

Free 

Vol. (cc/g) 5.36 6.79 5.72 7.38

 Pressure (MPa) 4.67 4.67 4.67 4.67 

SUMMARY OF ADSORPTION ANALYSES SI UNITS 

Isotherm Temperature: 28.0 oC 

Goodness of fit of Langmuir regression: 0.99 

% Ash = 6.37 % Moisture = 21.10 Density (g/cc) = 1.279 

Langmuir Parameters 

8.109 

9.245 

3.333 

4.071 

5.301 

6.660 

1.229 

1.707 

2.199 

2.698

 Pressure Adsorbed gas (cc/g) 

0.472 

0.791 

Sicahoy Bislig 1 

0.0 

1.0 

2.0 

3.0 

4.0 

5.0 

0.0 2.0 4.0 6.0 8.0 10.0 

Sample Cell Equilibrium Pressure (MPa) 

Methane Adsorbed (cc/g)

Dry ash free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A37
 (PSIA) As 

Received 

moisture 

free ash 

incl. 

ash free 

moisture 

incl. 

Dry Ash 

Free 

14.9 18.9 16.0 20.6 

25.3 32.1 27.1 34.9 

38.0 48.1 40.6 52.3 

49.4 62.5 52.7 68.0 

60.7 76.9 64.8 83.7 

69.7 88.4 74.5 96.1 

78.9 100.1 84.3 108.8 

86.7 109.8 92.5 119.5 

97.6 123.7 104.3 134.6 

108.2 137.1 115.5 149.1 

113.2 143.5 120.9 156.1 

119.6 151.6 127.7 164.9 

As 

Received 

Moisture 

free ash 

incl 

Ash free 

moisture 

incl 

Dry Ash 

Free

 Vol. (ft3

 /ton) 182.3 231.0 194.7 251.3 

Pressure (PSIA) 676.9 676.9 676.9 676.9 

SUMMARY OF ADSORPTION ANALYSES IMP. UNITS 

Isotherm Temperature: 82.4 oF 

Goodness of fit of Langmuir regression: 0.99 

% Ash = 6.37 % Moisture = 21.10 Density (g/cc) = 1.279 

Langmuir Parameters 

1176 

1341 

483 

590 

769 

966 

178 

248 

319 

391 

Pressure Adsorbed gas (ft3

 /ton) 

68 

115 

Sicahoy Bislig 1 

0 

50 

100 

150 

200 

250 

0 200 400 600 800 1000 1200 1400 

Sample Cell Equilibrium Pressure (PSIA) 

Methane Adsorbed (

SCF/t)

Dry Ash Free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A38
A39

Pressure/Volume (MPa*g/cc)

Adsorption Langmuir Plot

Surigo

Sample Sicahoy Bislig 1

2.5 2.0 1.5 1.0 0.5 0.0 

R2 = 0.991 

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 

Pressure (MPa) 

Dry ash 
 (MPa) As 

Received 

Moisture 

free ash 

incl. 

ash free 

moisture 

incl 

Dry Ash 

Free 

0.39 0.41 0.43 0.45 

1.46 1.53 1.62 1.70 

2.54 2.66 2.82 2.96 

3.86 4.02 4.27 4.48 

5.23 5.46 5.80 6.08 

6.55 6.83 7.25 7.61 

8.06 8.42 8.93 9.37 

9.58 10.01 10.62 11.14 

10.92 11.40 12.09 12.69 

12.08 12.61 13.38 14.03 

13.04 13.61 14.44 15.15 

13.83 14.43 15.32 16.07 

14.37 15.00 15.92 16.69 

As 

Received 

Moisture 

free ash 

incl. 

Ash free 

moisture 

incl 

Dry Ash 

Free 

Vol. (cc/g) 22.96 23.97 25.44 26.68

 Pressure (MPa) 5.53 5.53 5.53 5.53 

SUMMARY OF ADSORPTION ANALYSES SI UNITS 

Isotherm Temperature: 28.0 oC 

Goodness of fit of Langmuir regression: 0.99 

% Ash = 9.74 % Moisture = 4.21 Density (g/cc) = 1.446 

Langmuir Parameters 

6.950 

8.345 

10.077 

2.927 

3.926 

4.921 

5.935 

0.674 

1.102 

1.560 

2.076

 Pressure Adsorbed gas (cc/g) 

0.104 

0.413 

M-LC 

0.0 

5.0 

10.0 

15.0 

20.0 

25.0 

0.0 2.0 4.0 6.0 8.0 10.0 

Sample Cell Equilibrium Pressure (MPa) 

Methane Adsorbed (cc/g)

Dry ash free 

As received 

.Ash free moisture incl 

.Moisture free ash incl 

A40
 (PSIA) As 

Received 

moisture 

free ash 

incl. 

ash free 

moisture 

incl. 

Dry Ash 

Free 

13.3 13.9 14.7 15.5 

49.7 51.9 55.1 57.8 

86.6 90.4 95.9 100.6 

131.2 136.9 145.3 152.4 

178.1 185.9 197.3 207.0 

222.8 232.6 246.8 258.9 

274.3 286.4 303.9 318.8 

326.1 340.5 361.3 379.0 

371.4 387.8 411.5 431.6 

410.9 429.0 455.3 477.5 

443.6 463.1 491.5 515.5 

470.5 491.1 521.2 546.7 

488.8 510.3 541.6 568.0 

As 

Received 

Moisture 

free ash 

incl 

Ash free 

moisture 

incl 

Dry Ash 

Free

 Vol. (ft3

 /ton) 781.2 815.5 865.5 907.8 

Pressure (PSIA) 802.3 802.3 802.3 802.3 

SUMMARY OF ADSORPTION ANALYSES IMP. UNITS 

Isotherm Temperature: 82.4 oF 

Goodness of fit of Langmuir regression: 0.99 

% Ash = 9.74 % Moisture = 4.21 Density (g/cc) = 1.446 

Langmuir Parameters 

1008 

1210 

1462 

425 

569 

714 

861 

98 

160 

226 

301 

Pressure Adsorbed gas (ft3

 /ton) 

15 

60 

M-LC 

0 

100 

200 

300 

400 

500 

600 

700 

800 

0 500 1000 1500 

Sample Cell Equilibrium Pressure (PSIA) 

Methane Adsorbed (

SCF/t) 

Dry Ash Free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A41
0.7 

A42

Pressure/Volume (MPa*g/cc)

Adsorption Langmuir Plot

Zamboanga Sibuguey

Sample M-LC

0.6 0.5 0.4 

R2 = 0.9917 

0.0 2.0 4.0 6.0 8.0 10.

Pressure (MPa) 

Dry ash free 

0.3 0.2 0.1 0.0 
 (MPa) As 

Received 

Moisture 

free ash 

incl. 

ash free 

moisture 

incl 

Dry Ash 

Free 

0.49 0.52 0.79 0.89 

0.89 0.96 1.46 1.64 

1.61 1.73 2.63 2.96 

2.05 2.20 3.33 3.75 

2.73 2.93 4.45 5.01 

3.24 3.48 5.27 5.93 

4.10 4.41 6.68 7.52 

5.14 5.52 8.36 9.41 

5.57 5.98 9.07 10.21 

6.04 6.48 9.83 11.07 

6.55 7.03 10.66 11.99 

6.92 7.43 11.27 12.68 

7.36 7.90 11.98 13.48 

As 

Received 

Moisture 

free ash 

incl. 

Ash free 

moisture 

incl 

Dry Ash 

Free 

Vol. (cc/g) 12.90 13.85 21.00 23.64

 Pressure (MPa) 6.89 6.89 6.89 6.89 

SUMMARY OF ADSORPTION ANALYSES SI UNITS 

Isotherm Temperature: 28.0 oC 

Goodness of fit of Langmuir regression: 0.96 

% Ash = 38.58 % Moisture = 6.85 Density (g/cc) = 1.738 

Langmuir Parameters 

6.970 

8.320 

10.060 

3.006 

3.920 

4.964 

5.998 

0.942 

1.222 

1.756 

2.216

 Pressure Adsorbed gas (cc/g) 

0.332 

0.572 

M-LA 

0.0 

2.8 

5.6 

8.5 

11.3 

14.1 

16.9 

19.7 

0.0 2.0 4.0 6.0 8.0 10.0 

Sample Cell Equilibrium Pressure (MPa) 

Methane Adsorbed (cc/g) 

Dry ash free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A43
 (PSIA) As 

Received 

moisture 

free ash 

incl. 

ash free 

moisture 

incl. 

Dry Ash 

Free 

16.6 17.8 27.0 30.4 

30.4 32.7 49.6 55.8 

54.9 58.9 89.3 100.6 

69.7 74.8 113.5 127.7 

93.0 99.8 151.4 170.4 

110.2 118.3 179.3 201.8 

139.7 149.9 227.4 255.9 

174.8 187.7 284.6 320.3 

189.6 203.6 308.7 347.5 

205.5 220.6 334.6 376.5 

222.7 239.1 362.6 408.1 

235.5 252.8 383.4 431.5 

250.4 268.8 407.7 458.8 

As 

Received 

Moisture 

free ash 

incl 

Ash free 

moisture 

incl 

Dry Ash 

Free

 Vol. (ft3

 /ton) 438.9 471.2 714.6 804.3 

Pressure (PSIA) 999.4 999.4 999.4 999.4 

SUMMARY OF ADSORPTION ANALYSES IMP. UNITS 

Isotherm Temperature: 82.4 oF 

Goodness of fit of Langmuir regression: 0.96 

% Ash = 38.58 % Moisture = 6.85 Density (g/cc) = 1.738 

Langmuir Parameters 

1011 

1207 

1459 

436 

569 

720 

870 

137 

177 

255 

321 

Pressure Adsorbed gas (ft3

 /ton) 

48 

83 

M-LA 

0 

100 

200 

300 

400 

500 

600 

0 500 1000 1500 

Sample Cell Equilibrium Pressure (PSIA) 

Methane Adsorbed (

SCF/t) 

Dry Ash Free 

As received 

Ash free moisture incl. 

Moisture free ash incl. 

A44
A45

Pressure/Volume (MPa*g/cc)

Adsorption Langmuir Plot

Zamboanga Sibuguey

Sample M-LA

0.8 0.7 0.6 0.5 

R2 = 0.957 

0.0 2.0 4.0 6.0 8.0 10

Pressure (MPa) 

Dry ash f

0.4 0.3 0.2 0.1 0.0 
Your Isotherms 

To help you interpret you data I have prepared a few short paragraphs to tell you how 

your data was obtained. If you have any questions please do not hesitate to contact us. 

Obtaining and interpreting isotherm data and Langmuir Isotherms 

Your high-pressure methane, carbon dioxide or mixed gas adsorption analyses 

were performed using a high-pressure volumetric adsorption technique. Your isotherms 

were measured on a custom made apparatus modeled after an apparatus designed and 

built at CSIRO Lucus Heights, Australia. The apparatus is based on Boyles Law. 

Simply, a known volume of gas within in a reference cell is used to dose a sample cell 

containing your sample. The amount of gas adsorbed, using the real gas law, in the 

sample cell is then determined based on change in pressure in the sample cell. 

Normally 100 g of sample is utilized in such analyses. Tests show that reproducible 

results can be obtained on samples as small as 25 g but the larger samples yield better 

quality data. Our instrument has four sample cells. 

The pressures in the reference and four samples cells are measured using pressure 

transducers that are interfaced to a computer equipped with specialized boards and 

software for this purpose. The computer monitors the transducers and determines 

when equilibrium is reached as well as controls valves and switches for dosing and 

purging the references and sample cells. Following dosing of the sample cell with a 

known volume of gas, the pressure in the sample cell is monitored. As gas is adsorbed 

by the sample the pressure drops until equilibrium is reached; that is no more gas can 

be adsorbed by the samples at that particular specified pressure. Critical to obtaining 

quality isotherms is deciding when the equilibrium is reached. In our instrument we set 

a stringent test- equilibrium is reached only when the pressure in the cell does not 

change over a designated period of time. When equilibrium is reached the sample is 

dosed at the next highest pressure. We normally collect 12 separate pressure points 

selected such that the best Langmuir regression can be obtained. We can of course 

collect data at points selected by the client before hand. The temperature of the 

references and sample cells is maintained at the exact temperature requested by the 

client. The temperature is maintained within a tolerance less than 1/10 of one degree 

centigrade. 

For a routine adsorption analyses about five to six days are required once equilibrium 

moisture has been determined. 

A46
How we assure the quality of the isotherms- potential sources of error and 

recognition of problems 

With an apparatus such as ours the only potential error is a change in the 

characteristics of the pressure transducers, a leak in the system or non-isothermal 

conditions. 

Our pressure transducers were selected for optimum performance within the range of 

pressures that isotherms are collected. They are not only factory guaranteed we crosscalibrate our transducers periodically to test for drift. The accuracy of our transducers is 

better than 0.001 MPa. 

Prior to running your experiment the reference and sample cells and plumbing are 

pressure tested for leaks using helium. We do our leak tests at 9 MPa. Because the 

He molecule is smaller than either methane or carbon dioxide (the gases we normally 

do adsorption work with) using He assures us of a leak free system. If a leak were to 

develop during analyses (one never has) it would be readily apparent because the cells 

would never come to equilibrium at a given pressure (the leak would appear as an 

infinitely adsorbing material). 

Non-isothermal conditions are not a potential problem utilizing our instrument unless a 

prolonged power failure occurs. Our bath temperature is maintained by a submerged 

electric heater and a circulating power. The heater is controlled by a temperature 

controller to a tolerance less than 1/10 of a degree centigrade. 

We periodically run a standard sample in our apparatus to confirm that all is well. 

Understanding Your Isotherms 

The classic theory used to describe the Type I isotherm for microporous materials with 

small external surface area is based on the Langmuir equation (1916). The Type I 

isotherm displays a steep increase in adsorption at low relative pressures due to 

enhanced adsorption caused by the overlapping adsorption potentials between walls of 

pores whose diameters are commensurate in size with the adsorbate molecule. The 

Type I isotherm then flattens out into a plateau region at higher relative pressure, which 

is believed to be due to the completion of a monolayer of adsorbed gas. The micropore 

volume is then thought to be filled by only a few molecular layers of adsorbate, and 

further uptake is limited by the dimensions of the micropores. 

The Langmuir model assumes that a state of dynamic equilibrium is established 

between the adsorbate vapor and the adsorbent surface and that adsorption is 

restricted to a single monolayer (Gregg and Sing, 1982). The adsorbent surface is 

thought to be composed of a regular array of energetically homogeneous adsorption 

sites upon which an adsorbed monolayer is assumed to form. The rate of condensation 

A47
 is assumed to be equal to the rate of evaporation from the adsorbed monolayer at a 

given relative pressure and constant temperature. The Langmuir equation was 

developed with these assumptions and takes the following form:

 P = 1 + P

 V BVm Vm 

where P is the equilibrium pressure, V is the volume of gas adsorbed at equilibrium, Vm 

is the volume of adsorbate occupying a monolayer, and B is an empirical constant. A 

plot of P/V Vs relative pressure should yield a straight line whose slope will yield Vm 

from which the surface area may be obtained. As shown on your figures a best fit 

Langmuir isotherm and the data points have been plotted for each sample. 

The Langmuir Isotherm can be written: 

V PL V P( ) = P P L+

P = gas pressure 

V(P) = predicated amount of gas adsorbed at P 

VL = Langmuir volume parameter 

PL = Langmuir pressure parameter 

The difference between the measured amount of gas adsorbed (V(P)) and that 

predicted using the Langmuir Equation (Vi(P)) is a measure of error and is given as: 

Err(P) = Vi(P) - V(P) 

This error may be positive or negative. The square of the error is always positive and is 

a measure of the how well the calculated isotherm matches the data. This error can be 

calculate for each point and summed giving a measure of the overall error: 

N 2

SSE = ∑Err

i i=1

N= number of measured points. 

We express the goodness of fit of the isotherm by calculation the correlation coefficient 

between the measured points and the calculate points. Our results generally yield 

correlation's that are better than r2= 0.99. and standard errors of Langmuir volumes of ± 

2%. The errors for your samples can be found on the bottom of the data sheets that are 

included with each sample. 

A48 
In examining your data you should note that adsorption values are provided for the raw 

data and corrected for ash content. The ash content will also be corrected for 

equilibrium moisture content. 

References cited in appendix 

ICCP (International Committee for Coal and Organic Petrology), 1998, The new vitrinite 

classification (ICCP System, 1994), Fuel, vol. 77, p. 349-358. 

Langmuir, I., 1916. The constitution and fundamental properties of solids and liquids. 

Journal of the American Chemical Society, 38: 2221-2295. 

A49