Energy Yearbook - Definitions


The data on production refer to the first stage of production: accordingly, for hard coal the data refer to mine production; for briquettes to the output of briquetting plants; for crude petroleum and natural gas to production at oil and gas wells; for natural gas liquids to production at wells and processing plants; for refined petroleum products to gross refinery and plant output; for cokes and coke oven gas to the output of ovens; for other manufactured gas to production at gas works, blast furnaces or refineries; and for electricity to the gross production of generating plants.

Imports and Exports:
The international trade of energy commodities is based on the "general trade" system, that is, all goods entering and leaving the national boundary of a country are recorded as imports and exports.

refer to fuels supplied to ships and aircraft engaged in international transportation, irrespective of the carrier's flag.

Variation of stocks:
In general, data on stocks refer to changes in stocks at producers, importers and/or industrial consumers at the beginning and end of each year. In some cases, however, stock series have been derived on the basis of the difference between gross availabilities for transformation or consumption and official or published data on actual consumption. A positive stock change (+) reflects additions to stocks which in effect decreases "apparent consumption"; while a negative stock change (-) creates exactly the opposite result.

Data on consumption refer to "apparent consumption" and are derived from the formula "production + imports - exports - bunkers +/- stock changes." Accordingly, the series on apparent consumption may occasionally represent only an indication of the magnitude of actual (i.e., "measured") gross inland availability. This statement is particularly suitable either when stock data are unavailable or unreliable, or when apparent consumption is a small residual element derived from calculations between large aggregate series and thus is sensitive to small variations in these series. This latter point is also appropriate with respect to the per capita consumption calculations presented in some tables. Where the quantities involved are small, the series tend to exaggerate the effects of such elements as stock additions or withdrawals.



Hard coal:
Coal that has a high degree of coalification with a gross calorific value above 23,865 KJ/kg (5,700 kcal/kg) on an ash-free but moist basis, and a mean random reflectance of vitrinite of at least 0.6. Slurries, middlings and other low-grade coal products, which cannot be classified according to the type of coal from which they are obtained, are included under hard coal. There are two sub-categories of hard coal: (i) coking coal and (ii) other bituminous coal and anthracite (also known as steam coal). Coking coal is a hard coal with a quality that allows the production of coke suitable to support a blast furnace charge. Steam coal is coal used for steam raising and space heating purposes and includes all anthracite coals and bituminous coals not classified as coking coal.

One of the two sub-categories of brown coal. Brown coal is coal with a low degree of coalification which retained the anatomical structure of the vegetable matter from which it was formed. It has a mean random reflectance of vitrinite of less than 0.6, provided that the gross calorific value (on a moist ash-free basis) is less than 23,865 KJ/kg (5,700 kcal/kg). Brown coal comprises: (i) lignite - non-agglomerating coals with a gross calorific value less than 17,435 KJ/kg (4,165 kcal/kg) and greater than 31 per cent volatile matter on a dry mineral matter free basis and (ii) sub-bituminous coal - non-agglomerating coals with a gross calorific value between 17,435 KJ/kg (4,165 kcal/kg) and 23,865 KJ/kg (5,700 kcal/kg) containing more than 31 per cent volatile matter on a dry mineral matter free basis.

A solid fuel formed from the partial decomposition of dead vegetation under conditions of high humidity and limited air access (initial stage of coalification). Only peat used as fuel is included. Its principal use is as a household fuel.

Patent fuel (hard coal briquettes):
A composition fuel manufactured from coal fines by shaping with the addition of a binding agent such as pitch.

Lignite briquettes:
A composition fuel manufactured from lignite. The lignite is crushed, dried and molded under high pressure into an even shaped briquette without the addition of binders.

Peat briquettes:
A composition fuel manufactured from peat. Raw peat, after crushing and drying, is molded under high pressure into an even-shaped briquette without the addition of binders.

The solid residue obtained from coal or lignite by heating it to a high temperature in the absence or near absence of air. It is high in carbon and low in moisture and volatile matter. Several categories are distinguished:
a) Coke-oven coke - The solid product obtained from carbonization of coal, principally coking coal, at high temperature. Coke-oven coke is also called metallurgical coke and is used mainly in the iron and steel industry. Semi-coke, the solid product obtained from carbonization of coal at low temperature, is included with coke-oven coke. It is used mainly as a domestic fuel.
b) Gas coke - A by-product of coal used for the production of gas works gas in gasworks. Gas coke is mainly used as a domestic fuel.
c) Brown coal coke - A solid product obtained from carbonization of brown coal briquettes.

Oil shale:
A sedimentary rock containing a high proportion of organic matter (kerogen), which can be converted to crude oil or gas by heating.

Bituminous sands:
Sands or sandstones containing a high proportion of tarry hydrocarbons, capable of yielding oil through heating or other extractive processes. Heavy oils and tars which are so dense and viscous and lacking in primary energy that they cannot be produced commercially by conventional methods, that is, by natural flow or pumping, are also included.


Crude oil:
A mineral oil consisting of a mixture of hydrocarbons of natural origin, yellow to black in color, of variable density and viscosity. Data in this category also includes lease or field condensate (separator liquids) which is recovered from gaseous hydrocarbons in lease separation facilities, as well as synthetic crude oil, mineral oils extracted from bituminous minerals such as shales and bituminous sand, and oils from coal liquefaction.

Natural gas liquids (NGL):
Liquid or liquefied hydrocarbons produced in the manufacture, purification and stabilization of natural gas. NGL's include, but are not limited to, ethane, propane, butane, pentane, natural gasolene, and plant condensate. NGL's are either distilled with crude oil in refineries, blended with refined petroleum products or used directly depending on their characteristics.

Plant condensate:
Liquid hydrocarbons condensed from wet natural gas in natural gas processing plants. It is used as a petroleum refinery input.

Natural gasolene:
Light spirit extracted from wet natural gas, often in association with crude petroleum. It is used as a petroleum refinery and petrochemical plant input and is also used directly for blending with motor spirit without further processing.

Petroleum products:
Comprise the liquid fuels, lubricant oils and solid and semi solid products obtained by distillation and cracking of crude petroleum, shale oil, or semi refined and unfinished petroleum products. As far as possible the series include fuels consumed in refining, but exclude oil products obtained from natural gas, coal, lignite and their derivatives.

Aviation gasolene:
Motor spirit prepared especially for aviation piston engines, with an octane number varying from 80 to 145 RON and a freezing point of -60C.

Motor gasolene:
Light hydrocarbon oil for use in internal combustion engines such as motor vehicles, excluding aircraft. It distills between 35C and 200C, and is treated to reach a sufficiently high octane number of generally between 80 and 100 RON. Treatment may be by reforming, blending with an aromatic fraction, or the addition of benzole or other additives (such as tetraethyl lead).

Jet fuel:
Consists of gasolene-type jet fuel and kerosene-type jet fuel.

Gasolene-type jet fuel:
All light hydrocarbon oils for use in aviation gas-turbine engines. It distills between 100C and 250C with at least 20% of volume distilling at 143C. It is obtained by blending kerosene and gasolene or naphtha in such a way that the aromatic content does not exceed 25% in volume. Additives are included to reduce the freezing point to -58C or lower, and to keep the Reid vapour pressure between 0.14 and 0.21 kg/cm2.

Kerosene-type jet fuel:
Medium oil for use in aviation gas-turbine engines with the same distillation characteristics and flash point as kerosene, with a maximum aromatic content of 20% in volume. It is treated to give a kinematic viscosity of less than 15 cSt at -34C and a freezing point below -50C.

Medium oil distilling between 150C and 300C; at least 65% of volume distills at 250C. Its specific gravity is roughly 0.80 and its flash point is above 38C. It is used as an illuminant and as a fuel in certain types of spark-ignition engines, such as those used for agricultural tractors and stationary engines. Other names for this product are burning oil, vaporizing oil, power kerosene and illuminating oil.

Gas-diesel oil (distillate fuel oil):
Heavy oils distilling between 200C and 380C, but distilling less than 65% in volume at 250C, including losses, and 85% or more at 350C. Its flash point is always above 50C and its specific gravity is higher than 0.82. Heavy oils obtained by blending are grouped together with gas oils on the condition that their kinematic viscosity does not exceed 27.5 cSt at 38C. Also included are middle distillates intended for the petrochemical industry. Gas-diesel oils are used as a fuel for internal combustion in diesel engines, as a burner fuel in heating installations, such as furnaces, and for enriching water gas to increase its luminosity. Other names for this product are diesel fuel, diesel oil, gas oil and solar oil.

Residual fuel oil:
A heavy oil that makes up the distillation residue. It comprises all fuels (including those obtained by blending) with a kinematic viscosity above 27.5 cSt at 38C. Its flash point is always above 50C and its specific gravity is higher than 0.90. It is commonly used by ships and industrial large-scale heating installations as a fuel in furnaces or boilers.

Liquefied petroleum gas (LPG):
Hydrocarbons which are gaseous under conditions of normal temperature and pressure but are liquefied by compression or cooling to facilitate storage, handling and transportation. They are (i) extracted by stripping of natural gas at crude petroleum and natural gas sources; (ii) extracted by stripping of imported natural gas in installations of the importing country; and (iii) produced both in refineries and outside of refineries in the course of processing crude petroleum or its derivatives. It comprises propane (C3H8), butane (C4H10), or a combination of the two. Also included is ethane (C2H6) from petroleum refineries or natural gas producers' separation and stabilization plants.

Refinery gas:
Non-condensable gas obtained during distillation of crude oil or treatment of oil products (e.g. cracking) in refineries. It consists mainly of hydrogen, methane, ethane and olefins, and is used principally as a refinery fuel. Refinery gas is also known as still gas.

Products or a combination of products derived from crude oil destined for further processing in the refining industry other than blending. They are transformed into one or more components and/or finished products. This definition covers naphtha imported for refinery intake and naphtha returned from the chemical industry to the refining industry.

Light or medium oil distilling between 30C and 210C, for which there is no official definition, but which does not meet the standards laid down for motor spirit. The properties depend upon consumer specification. The C:H ratio is usually 84:14 or 84:16, with a very low sulphur content. Naphtha may be further blended or mixed with other materials to make high-grade motor gasolene or jet fuel, or may be used as a raw material for manufactured gas. Naphtha is sometimes used as input to feedstocks to make various kinds of chemical products, or may be used as a solvent.

White spirit/industrial spirit:
A highly refined distillate with a boiling point ranging from 135C to 200C, which is used as a paint solvent and for dry-cleaning purposes.

Viscous, liquid hydrocarbons rich in paraffin waxes, distilling between 380oC and 500oC, obtained by vacuum distillation of oil residues from atmospheric distillation. Additives may be included to alter their characteristics. Their main characteristics are: a flash point greater than 125C; a pour point between -25C and +5C depending on the grade; a strong acid number (normally 0.5 mg/g); an ash content less than or equal to 0.3%; and a water content less than or equal to 0.2%. Included are cutting oils, white oils, insulating oils, spindle oils and lubricating greases.

Solid or viscous hydrocarbon with a colloidal structure, brown or black in color, which is obtained as a residue by vacuum distillation of oil residues from atmospheric distillation. It is sometimes soluble in carbon bisulphite, non-volatile, thermoplastic (generally between 150C and 200C), often with insulating and adhesive properties. It is used mainly in road construction. Natural asphalt is excluded.

Petroleum waxes:
Saturated aliphatic hydrocarbons obtained as residues extracted when dewaxing lubricant oils, with a crystalline structure with C greater than 12. Their main characteristics are as follows: they are colorless, in most cases odorless and translucent; they have a melting point above 45C, a specific gravity of 0.76 to 0.78 at 80C, and a kinematic viscosity between 3.7 and 5.5 cSt at 99C. These waxes are used for candle manufacture, polishes and waterproofing of containers, wrappings, etc.

Petroleum coke:
A shiny, black solid residue obtained by cracking and carbonization in furnaces. It consists mainly of carbon (90 to 95%) and generally burns without leaving any ash. It is used mainly in metallurgical processes. It excludes those solid residues obtained from carbonization of coal.

Other petroleum products:
Products of petroleum origin (including partially refined products) not otherwise specified.


Natural gas - Gases consisting mainly of methane occurring naturally in underground deposits. It includes both non-associated gas (originating from fields producing only hydrocarbons in gaseous form) and associated gas (originating from fields producing both liquid and gaseous hydrocarbons), as well as methane recovered from coal mines and sewage gas. Production of natural gas refers to dry marketable production, measured after purification and extraction of natural gas liquids and sulphur. Extraction losses and the amounts that have been reinjected, flared, and vented are excluded from the data on production.

Gasworks gas - Gas produced by public utilities or private plants whose main activity is the production, transport and distribution of such gas. It includes gas produced by carbonization, by total gasification with or without enrichment with oil products, by cracking of natural gas, and by reforming or mixing gases.

Coke oven gas - By product of the carbonization process in the production of coke in coke ovens.

Blast furnace gas - By product in blast furnaces recovered on leaving the furnace.


Electricity production:
Refers to gross production, which includes the consumption by station auxiliaries and any losses in the transformers that are considered integral parts of the station. Included also is total electric energy produced by pumping installations without deduction of electric energy absorbed by pumping.
Production data includes Solar, Tide, Wave, Wind, Wastes, Wood and Fuel cell production when reported.

Public utilities:
Comprise the undertakings whose essential purpose is the production, transmission and distribution of electric energy, primarily for use by the public. These may be private companies, co operative organizations, local or regional authorities, nationalized undertakings or governmental organizations.

Self producers:
include undertakings which, in addition to their main activities, themselves produce (individually or in combination) electric energy intended, in whole or in part, to meet their own needs. They may be privately or publicly owned.

Primary electricity:
Refers to electrical energy of geothermal, hydro, nuclear, tide, wind, wave/ocean and solar origin. Its production is assessed at the heat value of electricity (3.6 TJ/million kWh).

Secondary electricity is defined as thermal electricity, which comprises conventional thermal plants of all types, whether or not equipped for the combined generation of heat and electric energy. Accordingly, they include steam operated generating plants, with condensation (with or without extraction) or with back pressure turbines and plants using internal combustion engines or gas turbines whether or not these are equipped for heat recovery.

Net installed capacity is measured at the terminals of the stations, i.e., after deduction of the power absorbed by the auxiliary installations and the losses in the station transformers, if any. Data concerning capacity refer in principle to 31 December of the year under consideration.

Imports and exports:
Refer to the amounts of electric energy transferred to and from the country concerned, respectively, which are measured at the metering points on the lines crossing the frontiers. Included are imports and exports of electric energy made by means of high voltage lines crossing frontiers as well as imports and exports made by means of low voltage lines for use in the immediate vicinity of the frontier, if the quantities so transferred are known.

Heat obtained from (a) combined heat and power (CHP) plants generating electricity and useful heat in a single installation; (b) district heating (DH) plants and (c) nuclear power plants and geothermal sources. The heat may be in the form of steam, hot water or hot air.

Uranium (U) production:
Comprises the U content of uranium ores and concentrates intended for treatment for uranium recovery.


All wood in the rough used for fuel purposes. Production data include the portion used for charcoal production, using a factor of 6 to convert from a weight basis to the volumetric equivalent (metric tons to cubic metres) of charcoal.

The cellulosic residue left after sugar is extracted from sugar cane. It is often used as a fuel within the sugar milling industry.

Solid residue, consisting mainly of carbon, obtained by the destructive distillation of wood in the absence of air.

Alcohol - Ethanol:
(ethyl alcohol) and methanol (methyl alcohol) for use as a fuel. Ethanol can be produced from sugar, starch and cellulose and is used mainly in transport (on its own or blended with gasolene). Methanol can be produced from wood, crop residues, grass, and the like and can be used in internal combustion engines.

Animal wastes:
Excreta of cattle, horses, pigs, poultry, etc., and (in principle) excreta of humans, used as a fuel.

Vegetal wastes:
Mainly crop residues (cereal straw from maize, wheat, paddy rice, etc.) and food processing wastes (rice hulls, coconut husks, ground nut shells, etc.) used for fuel. Bagasse is excluded.

Municipal wastes:
Consist of products that are combusted directly to produce heat and/or power and comprise wastes produced by the residential, commercial and public services sectors that are collected by local authorities for disposal in a central location. Hospital waste is included in this category.

Industrial wastes:
Consist of solid and liquid products other than solid biomass and animal products mentioned above (e.g. tires) combusted directly, usually in specialised plants, to produce heat and/or power.

Other wastes:
Wastes not specifically defined above, such as pulp and paper wastes.