Default Calorific Values

Default calorific values are the energy contents a compiler falls back on when specific, measured values are unavailable. IRES provides its own reference set — Table 4.1 below — for use as a last resort. The default values reproduced here are those used in the 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories (IPCC 2006); where the 2006 IPCC Guidelines report no value for a product, none is given in the table [IRES, Ch. IV, para. 4.45, PDF p. 61, 2018].

Table 4.1 — Default net calorific values for energy products

All values in GJ per metric ton unless otherwise noted [IRES, Ch. IV, Table 4.1, PDF pp. 61–63, 2018]:

Section/Division/Group	Class	Title	Default value	Lower value	Upper value
0		Coal
01		Hard coal
011	0110	Anthracite	26.7	21.6	32.2
012		Bituminous coal
	0121	Coking coal	28.2	24.0	31.0
	0129	Other bituminous coal	25.8	19.9	30.5
02		Brown coal
021	0210	Sub-bituminous coal	18.9	11.5	26.0
022	0220	Lignite	11.9	5.5	21.6
03		Coal products
031		Coal coke
	0311	Coke oven coke	28.2	25.1	30.2
	0312	Gas coke	28.2	25.1	30.2
	0313	Coke breeze
	0314	Semi cokes	28.2	25.1	30.2
032	0320	Patent fuel	20.7	15.1	32.0
033	0330	Brown coal briquettes (BKB)	20.7	15.1	32.0
034	0340	Coal tar	28.0	14.1	55.0
035	0350	Coke oven gas	38.7	19.6	77.0
036	0360	Gas works gas (and other manuf. gases for distribution)	38.7	19.6	77.0
037		Recovered gases
	0371	Blast furnace gas	2.47	1.20	5.00
	0372	Basic oxygen steel furnace gas	7.06	3.80	15.00
	0379	Other recovered gases
039	0390	Other coal products
1		Peat and peat products
11		Peat
111	1110	Sod peat	9.76	7.80	12.5
112	1120	Milled peat	9.76	7.80	12.5
12		Peat products
121	1210	Peat briquettes	9.76	7.80	12.5
129	1290	Other peat products	9.76	7.80	12.5
2		Oil shale/oil sands
20		Oil shale/oil sands
200	2000	Oil shale/oil sands	8.9	7.1	11.1
3		Natural gas
30		Natural gas
300	3000	Natural gas	48.0(a)	46.5	50.4
4		Oil
41		Conventional crude oil
410	4100	Conventional crude oil	42.3	40.1	44.8
42		Natural gas liquids (NGL)
420	4200	Natural gas liquids (NGL)	44.2	40.9	46.9
43		Refinery feedstocks
430	4300	Refinery feedstocks	43.0	36.3	46.4
44		Additives and oxygenates
440	4400	Additives and oxygenates
45		Other hydrocarbons
450	4500	Other hydrocarbons
46		Oil products
461	4610	Refinery gas	49.5	47.5	50.6
462	4620	Ethane	46.4	44.9	48.8
463	4630	Liquefied petroleum gases (LPG)	47.3	44.8	52.2
464	4640	Naphtha	44.5	41.8	46.5
465		Gasolines
	4651	Aviation gasoline	44.3	42.5	44.8
	4652	Motor gasoline	44.3	42.5	44.8
	4653	Gasoline-type jet fuel	44.3	42.5	44.8
466		Kerosenes
	4661	Kerosene-type jet fuel	44.1	42.0	45.0
	4669	Other kerosene	43.8	42.4	45.2
467		Gas oil/diesel oil and Heavy gas oil
	4671	Gas oil/diesel oil	43.0	41.4	43.3
	4672	Heavy gas oil
468	4680	Fuel oil	40.4	39.8	41.7
469		Other oil products
	4691	White spirit and special boiling point industrial spirits	40.2	33.7	48.2
	4692	Lubricants	40.2	33.5	42.3
	4693	Paraffin waxes	40.2	33.7	48.2
	4694	Petroleum coke	32.5	29.7	41.9
	4695	Bitumen	40.2	33.5	41.2
	4699	Other oil products n.e.c.	40.2	33.7	48.2
5		Biofuels
51		Solid biofuels
511		Fuelwood, wood residues and by-products	15.6	7.9	31.0
	5111	Wood pellets	17.3(b)
	5119	Other Fuelwood, wood residues and by-products	13.9(b)
512	5120	Bagasse
513	5130	Animal waste
514	5140	Black liquor	11.8	5.9	23.0
515	5150	Other vegetal material and residues
516	5160	Charcoal	29.5	14.9	58.0
52		Liquid biofuels
521	5210	Biogasoline	26.8(c)	13.6	54.0
522	5220	Biodiesels	36.8(c)	13.6	54.0
523	5230	Bio jet kerosene
529	5290	Other liquid biofuels	27.4	13.8	54.0
53		Biogases
531		Biogases from anaerobic fermentation
	5311	Landfill gas	50.4	25.4	100.0
	5312	Sewage sludge gas	50.4	25.4	100.0
	5319	Other biogases from anaerobic fermentation	50.4	25.4	100.0
532	5320	Biogases from thermal processes
6		Waste
61		Industrial waste
610	6100	Industrial waste
62		Municipal waste
620	6200	Municipal waste	11.6 / 10.0(d)	6.8 / 7.0(d)	18.0 / 18.0(d)
7		Electricity
70		Electricity
700	7000	Electricity
8		Heat
80		Heat
800	8000	Heat
9		Nuclear fuels and other fuels n.e.c.
91		Uranium and plutonium
910		Uranium and plutonium
	9101	Uranium ores
	9109	Other uranium and plutonium
92		Other nuclear fuels
920	9200	Other nuclear fuels
99		Other fuels n.e.c.
990	9900	Other fuels n.e.c.

Notes to Table 4.1 [IRES, Ch. IV, Table 4.1 notes, PDF p. 63, 2018]:

• (a) The table’s values are per mass, but natural gas calorific values are often expressed per volume instead. For example, United Nations (1988) gives an NCV of 39.02 GJ/thousand m³ under standard conditions for natural gas — a figure not derived from the value shown here.
• (b) Source: Austrian Energy Agency.
• (c) Source: IEA.
• (d) Values refer to the biomass/non-biomass fraction, respectively.

The SIEC codes and titles above match Table 3.1’s classification; see Coal, Biofuels and Waste for the underlying product definitions.

Fuelwood

Fuelwood — the principal cooking/heating energy source in rural areas of many developing countries — is poorly captured in statistics, largely because it is often produced by households for their own use or traded informally [IRES, Ch. IV, para. 4.46, PDF p. 64, 2018]. Wood species and moisture/ash content vary widely and strongly affect calorific value, so countries are encouraged to identify typical fuelwood mixes and average water content, and to establish country-specific volume-to-mass conversion factors [IRES, Ch. IV, para. 4.47, PDF p. 64, 2018].

Fuelwood can be measured by volume (stacked — the stere/stacked cubic metre, or the cord of 128 stacked cubic feet — or solid volume, via water displacement) or by weight. Volume measurement is relatively insensitive to moisture content; weight is highly sensitive to it, since more water per unit weight means less actual fuelwood, so moisture content must be accurately specified whenever fuelwood is weighed [IRES, Ch. IV, para. 4.48, PDF p. 64, 2018].

Moisture content (mc) is measured on two possible bases:

Dry basis: mc% = [(wet weight − dry weight) / dry weight] × 100

Wet basis: mc% = [(wet weight − dry weight) / wet weight] × 100

[IRES, Ch. IV, para. 4.49, PDF p. 64, 2018]

The two bases diverge sharply for very wet biomass (100% mc dry basis = 50% mc wet basis) but converge for air-dry biomass (15% mc dry basis ≈ 13% mc wet basis); it is important to state which basis is used, and most (not all) fuelwood moisture is reported on a dry basis [IRES, Ch. IV, para. 4.50, PDF p. 64, 2018].

Ash content is a second determinant of fuelwood’s energy value: generally around 1 per cent for fuelwood, but up to 4 per cent for some species, since the substances forming ash carry no energy value — wood with 4% ash content has roughly 3% less energy content than wood with 1% ash content [IRES, Ch. IV, para. 4.51, PDF p. 64, 2018].

Default calorific values for fuelwood (mass to energy) vary with the moisture content of green, air-dried and oven-dried wood, as shown in Table 4.2 [IRES, Ch. IV, para. 4.52, PDF p. 64, 2018]. When fuelwood is collected in volume units, Table 4.3 gives the conversion factors to mass units [IRES, Ch. IV, para. 4.53, PDF p. 65, 2018].

Table 4.2 — Influence of moisture content on net calorific values of standard fuelwood (wood with 1% ash content)

[IRES, Ch. IV, Table 4.2, PDF p. 65, 2018]

Wood state	Dry basis	Wet basis	Kilocalories per kilogram	Btus per pound	Megajoules per kilogram
Green wood	160	62	1 360	2 450	5.7
Green wood	140	59	1 530	2 750	6.4
Green wood	120	55	1 720	3 100	7.2
Green wood	100	50	1 960	3 530	8.2
Green wood	80	45	2 220	4 000	9.3
Green wood	70	41	2 390	4 300	10.0
Green wood	60	38	2 580	4 640	10.8
Air-dried wood	50(a)	33(a)	2 790	5 030	11.7
Air-dried wood	40	29	3 030	5 460	12.7
Air-dried wood	30	23	3 300	5 930	13.8
Air-dried wood	25(b)	20(b)	3 460	6 230	14.5
Air-dried wood	20	17	3 630	6 530	15.2
Oven-dried wood	15	13	3 820	6 880	16.0
Oven-dried wood	10	9	4 010	7 220	16.8
Oven-dried wood	5	5	4 230	7 610	17.7
Oven-dried wood	0	0	4 470	8 040	18.7

Notes: (a) average of as-received fuelwood on cordwood basis (4-foot lengths); (b) average of logged fuelwood. Source: United Nations (1987) [IRES, Ch. IV, Table 4.2 notes, PDF p. 65, 2018].

Table 4.3 — Conversion table for fuelwood (wood with 25% moisture content)

[IRES, Ch. IV, Table 4.3, footnote 37, PDF p. 65, 2018]

Fuelwood	Metric tons per solid cubic metre	Metric tons per cord	Stacked cubic metres (stere) per metric ton
General	0.707	1.71	2.12
Coniferous	0.570	1.38	2.63
Non-Coniferous	0.742	1.79	2.02

Cubic metre measured under bark at 25% moisture content (dry basis); weight includes bark. “General” is weighted 20% coniferous / 80% non-coniferous. Source: Forest Products Conversion Factors for the UNECE Region, UNECE/FAO, 2010, updated 2015 [IRES, Ch. IV, Table 4.3, footnote 37, PDF p. 65, 2018].

Annex B, Table 5 — Influence of moisture on solid volume and weight of standard fuelwood:

Percentage moisture content of fuelwood:

	100	80	60	40	20	15	12	10	0
Solid volume in m³ per ton	0.80	0.89	1.00	1.14	1.33	1.39	1.43	1.45	1.60
Weight in tons per m³	1.25	1.12	1.00	0.88	0.75	0.72	0.70	0.69	0.63

Source: United Nations (1987) [IRES, Annex B, Table 5, PDF p. 163, 2018].

Charcoal

The amount of biomass (usually fuelwood) needed to yield a given quantity of charcoal depends mainly on three factors: parent wood density, moisture content, and the means of production [IRES, Ch. IV, para. 4.54, PDF p. 65, 2018].

Wood density is the principal yield determinant — charcoal weight can vary by a factor of 2 for equal volumes of input. Drier wood yields more charcoal. The means of production also matters: charcoal is produced in earth-covered pits, oil drums, brick or steel kilns, and retorts, with less sophisticated methods generally losing more powdered charcoal (fines), leaving more incomplete carbonization, and combusting more of the charcoal product itself, all of which lower yields [IRES, Ch. IV, para. 4.55, PDF p. 65, 2018]. Powdered charcoal is always produced during manufacture and transport; when briquetted, the briquettes can weigh 50–100% more per given volume of un-powdered charcoal, owing to greater density [IRES, Ch. IV, para. 4.56, PDF pp. 65–66, 2018].

Three variables determine charcoal’s energy value: moisture content, ash content, and degree of carbonization. Average charcoal moisture content is 5%. Average ash content is 4% for wood charcoal, but near 20% for charcoal from woody crop residues (e.g. coffee shrubs). Assuming complete carbonization, wood charcoal (4% ash, 5% moisture) averages ~30.8 MJ/kg; crop-residue charcoal (20% ash, 5% moisture) averages ~25.7 MJ/kg [IRES, Ch. IV, paras. 4.57–4.58, PDF p. 66, 2018].

Annex B, Table 6 — Fuelwood to charcoal conversion table.

Influence of parent wood density on charcoal production (weight in kg of charcoal produced per cubic metre of fuelwood):

Coniferous wood	Average tropical hardwoods	Preferred tropical hardwoods	Mangrove (rhizophora)
115	170	180	285

Influence of wood moisture content on charcoal production (quantity of wood required to produce 1 ton of charcoal):

Moisture content (dry basis)	100	80	60	40	20	15	10
Volume of wood required (cubic metres)	17.6	16.2	13.8	10.5	8.1	6.6	5.8
Weight of wood required (tons)	12.6	11.6	9.9	7.5	5.8	4.7	4.1

Source: United Nations (1987) [IRES, Annex B, Table 6, PDF p. 163, 2018].

Annex B, Table 7 — Fuelwood requirement for charcoal production by kiln type (cubic metres of fuelwood per ton of charcoal, by percentage moisture content of fuelwood):

Kiln Type	15	20	40	60	80	100
Earth kiln	10	13	16	21	24	27
Portable steel kiln	6	7	9	13	15	16
Brick kiln	6	6	7	10	11	12
Retort	4.5	4.5	5	7	8	9

Data are based on the assumption of standard hardwood as input into the process. Source: United Nations (1987) [IRES, Annex B, Table 7, PDF p. 164, 2018].

Vegetal and animal wastes

Agricultural wastes and food-processing by-products are used as fuel, substituting for woody biomass in fuelwood-deficient areas [IRES, Ch. IV, para. 4.59, PDF p. 66, 2018].

Moisture and ash content are the two key determinants of non-woody plant biomass’s energy value: wood’s ash content is generally ~1%, but crop residues range from 3% to over 20%, and — as with fuelwood — ash carries no energy value, so 20%-ash biomass has roughly 19% less energy than otherwise-similar 1%-ash biomass. Such data are rarely collected directly and are usually derived from crop/waste or end-product/waste ratios. Given the wide cross-country variability in ash and moisture content, it is recommended that animal and vegetal wastes be reported to international organizations in an energy unit (preferably TJ) rather than their natural units — national authorities are generally best placed to assess these wastes’ energy content, alternatively estimable from the measured heat or electricity output of the transformation devices that use them, applying standard efficiency factors [IRES, Ch. IV, para. 4.60, PDF p. 66, 2018].

Bagasse: two worked estimation methods

Bagasse — the fibrous cane residue from sugar production — is important enough, and compositionally consistent enough, that international organizations report it separately from ordinary vegetal waste, in its natural (weight) unit, rather than folding it into the general recommendation above. Its availability can be estimated from either the sugar cane input to sugar mills or the output of centrifugal cane sugar [IRES, Ch. IV, para. 4.61, PDF p. 66, 2018].

Method (a) — Central American studies. Fuel bagasse yield is approximately 280 kg per metric ton of sugar cane processed. Assuming 50% moisture content at time of use, 1 metric ton of bagasse yields 7.72 GJ. For 1 metric ton of processed sugar cane, this gives:

2.16 GJ = 0.516 Gcal = 0.074 tce = 0.051 toe

[IRES, Ch. IV, para. 4.62, PDF p. 66, 2018]

Method (b) — Economic Commission for Latin America and the Caribbean (ECLAC). Based on observations, ECLAC proposed 3.26 kg bagasse yield per kilogram of centrifugal sugar produced. For 1 metric ton of sugar produced, this gives:

25.2 GJ = 6 Gcal = 0.86 tce = 0.59 toe

[IRES, Ch. IV, para. 4.63, PDF p. 67, 2018]

The two methods are not interchangeable estimates of the same quantity — method (a) is per ton of sugar cane processed, method (b) per ton of sugar produced — and IRES presents both without recommending one over the other.

Animal waste (dung) is another significant agricultural by-product: it can be dried and burned directly for space heating, cooking or crop drying; fed into biogas digestors (yielding gas for cooking/heating/lighting plus a fertilizer residue); used as biodiesel feedstock; or spread with minimal treatment as fertilizer [IRES, Ch. IV, para. 4.64, PDF p. 67, 2018].

Annex B, Table 8 — Energy values of selected animal and vegetal wastes:

Wastes	Average moisture content: dry basis (percentage)	Approximate ash content (percentage)	Net calorific value (MJ/kg)
Animal dung	15	23–27	13.6
Groundnut shells	3–10	4–14	16.7
Coffee husks	13	8–10	15.5–16.3
Bagasse	40–50	10–12	8.4–10.5
Cotton husks	5–10	3	16.7
Coconut husks	5–10	6	16.7
Rice hulls	9–11	15–20	13.8–15.1
Olives (pressed)	15–18	3	16.75
Oil-palm fibres	55	10	7.5–8.4
Oil-palm husks	55	5	7.5–8.4
Bagasse	30	10–12	12.6
Bagasse	50	10–12	8.4
Bark	15	1	11.3
Coffee husk, cherries	30	8–10	13.4
Coffee husk, cherries	60	8–10	6.7
Corncobs	15	1–2	19.3
Nut hulls	15	1–5	18.0
Rice straw & husk	15	15–20	13.4
Wheat straw & husk	15	8–9	19.1
Municipal garbage	..	..	19.7
Paper	5	1	17.6
Sawdust	50	1	11.7

Note: two dots (..) indicate that data are not available. Source: United Nations (1987) [IRES, Annex B, Table 8, PDF p. 164, 2018]. Bagasse appears three times in the source table at different moisture contents (40–50%, 30%, 50%) — reproduced as three separate rows, not merged, since each row is a distinct moisture-content observation.

Related

• IRES Annexes and References — Annex B, Tables 5–8, the source of the fuelwood-moisture, charcoal-conversion and animal/vegetal-waste tables above
• Calorific Values — the general default-vs-specific distinction and the weighted-average calculation method this table backs
• Measurement Units — the mass, volume and energy units Table 4.1 and the biomass tables are expressed in
• Coal — coal, peat and coal-product classes whose default NCVs appear in Table 4.1
• Biofuels — fuelwood, charcoal, bagasse and biogas classes whose default NCVs and biomass-specific determination methods are detailed above
• Waste — industrial/municipal waste default NCVs in Table 4.1