# Chapter III. Standard International Energy Product Classification ## A. Introduction 3.1. In order to ensure cross-country and temporal comparability of energy statistics, as well as their comparability with other statistics, it is of paramount importance to have internationally agreed definitions of energy products and their classification. Such definitions and classification should be promoted as a basic tool for energy statistics compilation and dissemination both at national and international levels. 3.2. This chapter presents the list of internationally agreed definitions of energy products and the Standard International Energy Product Classification (SIEC), which arranges them in the structure of a statistical classification. The chapter contains a description of the purpose and scope of SIEC, and presents the classification criteria and the classification itself. In addition, correspondences between SIEC and other international product classifications, such as the Harmonized Commodity Description and Coding System (HS) and the Central Product Classification (CPC) are provided. These correspondences facilitate the integration of energy statistics with other economic statistics, thereby increasing their analytical value. 3.3. The correspondence with the HS is particularly useful as all international transactions in energy products are defined in terms of HS. Many energy products are widely traded internationally and energy companies are familiar with HS or its national equivalents. The correspondence with HS is expected to facilitate data collection, as the documentation that energy importing/exporting companies provide for customs purposes includes the relevant HS codes. The CPC aggregates the HS headings into product groupings which are of particular interest for economic statistics and for various users. 3.4. The correspondence with HS and CPC presented in the chapter is indicative in the sense that the HS and CPC categories are often broader in scope and may contain more elements than the corresponding SIEC category.[^17] However, in the case of national or regional adaptations of the HS (such as the European Combined Nomenclature), the correspondences may be more precise. This applies in particular to the categories for refined petroleum products. ## B. Purpose and scope of SIEC 3.5. The main purpose of SIEC is to serve as a basis for developing or revising national classification schemes for energy products so as to make them compatible with international standards and, consequently, to ensure significantly improved cross-country comparability of energy data. SIEC is intended to be a multipurpose classification, meaning that individual SIEC products and aggregates are defined to be suitable for the production of energy statistics under different country circumstances and are relevant for the presentation and analysis of energy data in various policy and analytical contexts. In this connection, it is recognized that SIEC should be periodically reviewed and revised as necessary to reflect changes in the patterns of energy production and consumption. 3.6. SIEC is designed to support the collection of data from data reporters and will: (i) facilitate and standardize the compilation and processing of energy data by providing a uniform and hierarchical coding system; (ii) ensure international comparability of disseminated national data; and (iii) facilitate the linking of data on stocks and flows of energy products with data on international trade in energy products and other economic statistics. 3.7. SIEC aims to cover all products necessary to provide a comprehensive picture of the production, transformation and consumption of energy throughout an economy. Thus the scope of SIEC consists of the following:[^18] (a) Fuels[^19] that are produced/generated by an economic unit (including households), and are used or might be used as sources of energy; and (b) Electricity that is generated by an economic unit (including households), and heat generated and sold to third parties by an economic unit. 3.8. In order to define the scope of SIEC more precisely, the fuel coverage is further explained below. (i) All fossil fuels[^20] are within the scope of SIEC whether or not they are used for energy purposes, but an exception is made for peat used for non-energy purposes, which should be excluded. (ii) Products derived from fossil fuels are always within the scope of SIEC when used (or intended to be used) for energy purposes, i.e. as fuels. (iii) Products derived from fossil fuels used (or intended to be used) for non-energy purposes are within the scope only if they are the output of energy industries (e.g. refineries, gas plants or coal mining, coal manufacturing industries). They are included because they explain how much an apparent supply of energy is used for other purposes and allow for a complete assessment of the industries involved. 3.9. One example of products in category (iii) mentioned above are lubricants produced during the refining of crude oil. Even though they are ordinarily used for non-energy purposes, their production and consumption are recorded in energy statistics as this allows for the monitoring of the different products obtained from the refinery intake of crude oil and the assessment of the part of crude oil used for non-energy purposes. This is of relevance to energy planners, provided that the consumption of these products is explicitly identified as non-energy use. On the other hand, plastics, even if derived from a fossil fuel such as crude oil, are not considered within the scope of SIEC as they are not an output of the refinery but are obtained by further processing of refinery products by other industries. 3.10. Some fuels such as waste,[^21] agricultural crops or other biomass are not of fossil origin. Such products are within the scope of SIEC only when used for energy purposes. Thus, the inclusion of these products in total energy production depends on their use, i.e. it is derived from demand-side information. 3.11. In IRES, the term energy product is defined as any product covered by the scope of SIEC, as formulated above. 3.12. It should be noted that, while SIEC provides definitions for all energy products, the scope of individual applications of energy statistics may cover just a subset of SIEC. For example, while SIEC includes nuclear fuels in the scope of energy products, they are not used in energy balances. ## C. Classification criteria and coding system 3.13. The SIEC categories are designed to be exhaustive and mutually exclusive, so that any product within the general scope would belong to only one SIEC category for any given application.[^22] At the highest level, SIEC provides ten sections for different fuels, electricity and heat. The eight fuel categories represent broad fuel types distinguished by their origin and characteristics, covering coal, peat and peat products, oil shale/oil sands, natural gas, oil, biofuels, waste, nuclear fuels and other fuels. Where applicable, these fuel categories are further disaggregated by physical characteristics (e.g. brown coal vs. hard coal) and stage of processing. In the latter case, in each section the unprocessed products appear first (in order of the coding system), followed by processed products. For some of the fuel categories, reference to the use is made since the specifications of the product make it fit for certain types of use (e.g., kerosene and its disaggregation into kerosene-type jet fuel and other kerosene). 3.14. Some products in SIEC, although physically similar, may be considered as different products due to different origin or intended use. For instance, several of the included gases may contain similar chemical components, but originate from different processes. This is the case for the categories natural gas and landfill gas, both of which consist mainly of methane, but differ in their source and method of production. Likewise, natural gas liquids and liquefied petroleum gas both contain propane, but the latter category refers to a mix of gases that only contains propane and butane, whereas the former category represents a less refined mix of gases. Another example is the category feedstocks, which may consist of energy products that can be found in other categories (e.g., naphtha) but are characterized by the fact of being destined for a particular use. 3.15. The top-level categories representing electricity and heat are not further disaggregated in the classification. Unlike fuels, these products are not physical substances that can easily be distinguished by origin, composition or intended purpose. Electricity and heat can be produced through different processes, such as direct conversion of the energy in solar radiation, falling water or release through combustion of fuels. The distinction between different production processes is important for energy statistics and may be obtained by disaggregating information on the production side (see chapter V for more details). 3.16. The distinctions between primary and secondary energy products, as well as between renewable and non-renewable energy products, are not explicit classification criteria in SIEC, although in many cases a complete detailed SIEC category can clearly be assigned to one set. The list of products considered primary or secondary and renewable or non-renewable is given in annex A. ### Coding system 3.17. The SIEC hierarchy consists of four levels referred to as sections (the first level), divisions (the second level), groups (the third level), and classes (the fourth level). The coding system consists of a four-digit numerical code, with the first digit referring to the section, the first two digits to the division, and so on. Thus, all four digits, taken together, designate a particular class of the classification. 3.18. The hierarchy groups basic categories into higher-level aggregations according to the criteria described above. The purpose is to provide a set of levels, with each level being used to provide statistical information that is analytically useful. **Table 3.1 — Standard International Energy Product Classification (SIEC)** | Section/Division/Group | Class | Title | CPC Ver.2 | HS 2007 | | --- | --- | --- | --- | --- | | 0 | | Coal | | | | 01 | | Hard coal | | | | 011 | 0110 | Anthracite | 11010* | 2701.11 | | 012 | | Bituminous coal | | | | | 0121 | Coking coal | 11010* | 2701.19 | | | 0129 | Other bituminous coal | 11010* | 2701.12 | | 02 | | Brown coal | | | | 021 | 0210 | Sub-bituminous coal | 11030* | 2702.10* | | 022 | 0220 | Lignite | 11030* | 2702.10* | | 03 | | Coal products | | | | 031 | | Coal coke | | | | | 0311 | Coke oven coke | 33100* | 2704* | | | 0312 | Gas coke | 33100* | 2704* | | | 0313 | Coke breeze | 33100* | 2704* | | | 0314 | Semi cokes | 33100* | 2704* | | 032 | 0320 | Patent fuel | 11020 | 2701.20 | | 033 | 0330 | Brown coal briquettes (BKB) | 11040 | 2702.20 | | 034 | 0340 | Coal tar | 33200* | 2706 | | 035 | 0350 | Coke oven gas | 17200* | 2705* | | 036 | 0360 | Gas works gas (and other manufactured gases for distribution) | 17200* | 2705* | | 037 | | Recovered gases | | | | | 0371 | Blast furnace gas | 17200* | 2705* | | | 0372 | Basic oxygen steel furnace gas | 17200* | 2705* | | | 0379 | Other recovered gases | 17200* | 2705* | | 039 | 0390 | Other coal products | 33500*, 34540* | 2707, 2708.10*, 2708.20*, 2712.90* | | 1 | | Peat and peat products | | | | 11 | | Peat | | | | 111 | 1110 | Sod peat | 11050* | 2703* | | 112 | 1120 | Milled peat | 11050* | 2703* | | 12 | | Peat products | | | | 121 | 1210 | Peat briquettes | 11050* | 2703* | | 129 | 1290 | Other peat products | 11050*, 33100*, 33200*, 33500* | 2703*, 2704*, 2706*, 2712.90* | | 2 | | Oil shale/oil sands | | | | 20 | | Oil shale/oil sands | | | | 200 | 2000 | Oil shale/oil sands | 12030 | 2714.10 | | 3 | | Natural gas | | | | 30 | | Natural gas | | | | 300 | 3000 | Natural gas | 12020 | 2711.11, 2711.21 | | 4 | | Oil | | | | 41 | | Conventional crude oil | | | | 410 | 4100 | Conventional crude oil | 12010* | 2709* | **Table 3.1 — Standard International Energy Product Classification (SIEC) (continued)** | Section/Division/Group | Class | Title | CPC Ver.2 | HS 2007 | | --- | --- | --- | --- | --- | | 42 | | Natural gas liquids (NGL) | | | | 420 | 4200 | Natural gas liquids (NGL) | 33420* | 2711.14, 2711.19*, 2711.29* | | 43 | | Refinery feedstocks | | | | 430 | 4300 | Refinery feedstocks | (a) | (a) | | 44 | | Additives and oxygenates | | | | 440 | 4400 | Additives and oxygenates | 34131*, 34139*, 34170*, others | 2207.20*, 2905.11, 2909.19*, others | | 45 | | Other hydrocarbons | | | | 450 | 4500 | Other hydrocarbons | 12010*, 34210* | 2709*, 2804.10 | | 46 | | Oil products | | | | 461 | 4610 | Refinery gas | 33420* | 2711.29* | | 462 | 4620 | Ethane | 33420* | 2711.19*, 2711.29* | | 463 | 4630 | Liquefied petroleum gases (LPG) | 33410 | 2711.12, 2711.13 | | 464 | 4640 | Naphtha | 33330* | 2710.11* | | 465 | | Gasolines | | | | | 4651 | Aviation gasoline | 33310* | 2710.11* | | | 4652 | Motor gasoline | 33310* | 2710.11* | | | 4653 | Gasoline-type jet fuel | 33320 | 2710.11* | | 466 | | Kerosenes | | | | | 4661 | Kerosene-type jet fuel | 33342 | 2710.19* | | | 4669 | Other kerosene | 33341 | 2710.19* | | 467 | | Gas oil/diesel oil and heavy gas oil | | | | | 4671 | Gas oil/diesel oil | 33360* | 2710.19* | | | 4672 | Heavy gas oil | 33360* | 2710.19* | | 468 | 4680 | Fuel oil | 33370 | 2710.19* | | 469 | | Other oil products | | | | | 4691 | White spirit and special boiling point industrial spirits | 33330* | 2710.11* | | | 4692 | Lubricants | 33380* | 2710.19* | | | 4693 | Paraffin waxes | 33500* | 2712.20* | | | 4694 | Petroleum coke | 33500*, 34540* | 2708.20*, 2713.11, 2713.12 | | | 4695 | Bitumen | 33500* | 2713.20 | | | 4699 | Other oil products n.e.c. | 33330*, 33350*, 33380*, 33420*, 33500*, 34540* | 2707*, 2708.10*, 2710.11*, 2710.19*, 2711.14*, 2712.10*, 2712.20*, 2712.90*, 2713.90 | | 5 | | Biofuels | | | | 51 | | Solid biofuels | | | | 511 | | Fuelwood, wood residues and by-products | | | | | 5111 | Wood pellets | 39280* | 4401.30* | | | 5119 | Other fuelwood, wood residues and by-products | 03130, 31230, 39280* | 4401.10, 4401.21, 4401.22, 4401.30* | | 512 | 5120 | Bagasse | 39140* | 2303.20* | | 513 | 5130 | Animal waste | 34654* | 3101* | | 514 | 5140 | Black liquor | 39230* | 3804.00* | **Table 3.1 — Standard International Energy Product Classification (SIEC) (continued)** | Section/Division/Group | Class | Title | CPC Ver.2 | HS 2007 | | --- | --- | --- | --- | --- | | 515 | 5150 | Other vegetal material and residues | 01913, 21710, 34654*, 39120*, 39150* | 0901.90*, 1213, 1802*, 2302*, 2304, 2305, 2306, 3101 | | 516 | 5160 | Charcoal | 34510 | 4402 | | 52 | | Liquid biofuels | | | | 521 | 5210 | Biogasoline | 34131*, 34139*, 34170* | 2207.20*, 2905.11*, 2905.13*, 2905.14*, 2909.19* | | 522 | 5220 | Biodiesels | 35490* | 3824.90* | | 523 | 5230 | Bio jet kerosene | | | | 529 | 5290 | Other liquid biofuels | | | | 53 | | Biogases | | | | 531 | | Biogases from anaerobic fermentation | | | | | 5311 | Landfill gas | 33420* | 2711.29* | | | 5312 | Sewage sludge gas | 33420* | 2711.29* | | | 5319 | Other biogases from anaerobic fermentation | 33420* | 2711.29* | | 532 | 5320 | Biogases from thermal processes | | | | 6 | | Waste | | | | 61 | | Industrial waste | | | | 610 | 6100 | Industrial waste | 3921, 39220, 39240, 39250, 39260, 39270, 39290 | 2525.30, 2601, 3915, 4004, 4012.20, 4115.20, 4707, 5003, 5103.20, 5103.30, 5104, 5202, 5505, 6309, 6310 | | 62 | | Municipal waste | | | | 620 | 6200 | Municipal waste | 39910 | 3825.10 | | 7 | | Electricity | | | | 70 | | Electricity | | | | 700 | 7000 | Electricity | 17100 | 2716 | | 8 | | Heat | | | | 80 | | Heat | | | | 800 | 8000 | Heat | 17300 | 2201.90* | | 9 | | Nuclear fuels and other fuels n.e.c. | | | | 91 | | Uranium and plutonium | | | | 910 | | Uranium and plutonium | | | | | 9101 | Uranium ores | 13000* | 2612.10 | | | 9109 | Other uranium and plutonium | 33610, 33620, 33630*, 33710, 33720 | 2844.10, 2844.20, 2844.30*, 2844.50, 8401.30 | | 92 | | Other nuclear fuels | | | | 920 | 9200 | Other nuclear fuels | 33630*, 33690* | 2844.30*, 2844.40* | | 99 | | Other fuels n.e.c. | | | | 990 | 9900 | Other fuels n.e.c. | | | > **Notes to table 3.1:** > - Coal products refer to the products derived from hard coal and brown coal. Peat products refer to products derived from peat. Oil products refer to products derived from the processing of conventional crude oil, NGLs, other hydrocarbons, refinery feedstocks, etc. > - An asterisk (*) next to a CPC or HS code indicates that this link is a partial link only. > - (a) Since the definition of feedstocks is primarily based on intended use, giving an explicit CPC/HS link could be misleading. Feedstocks may cover a wider range of products, including naphthas (HS 2710.11) and pyrolysis gasoline (HS 2707.50) among others. > - Descriptions and definitions of the CPC and HS codes can be accessed on the websites of their custodians, the United Nations Statistics Division (UNSD) and the World Customs Organization (WCO), respectively. > - Revised correspondence tables between SIEC and updated versions of the CPC or HS are available on the UNSD Classifications website at http://unstats.un.org/unsd/class. ## D. Definitions of energy products 3.19. The list of internationally agreed definitions of the products in SIEC is provided below. The definitions are the result of the work of the InterEnerStat and have been reviewed and supported by the Oslo Group on Energy Statistics and the United Nations Expert Group on Energy Statistics.[^23] The definitions of particular products are followed, whenever necessary, by remarks providing additional clarifications. In cases where a SIEC category is identical at different levels, i.e. not further subdivided, only the code at the higher level is shown. The definition naturally applies also to the item at the lower level of the classification. **0 Coal** This section includes coal, i.e. solid fossil fuel consisting of carbonized vegetal matter and coal products derived directly or indirectly from the various classes of coal by carbonization or pyrolysis processes, by the aggregation of finely divided coal or by chemical reactions with oxidizing agents, including water. Remark: There are two main categories of primary coal, hard coal (comprising medium- and high-rank coals) and brown coal (low-rank coals), which can be identified by their Gross Calorific Value (GCV) and the vitrinite mean random reflectance percentage (Rr). Peat is not included here. **01 Hard coal** Coals with a gross calorific value (moist, ash-free basis) which is not less than 24 MJ/kg, or which is less than 24 MJ/kg, provided that the coal has a vitrinite mean random reflectance greater than or equal to 0.6 per cent. Hard coal comprises anthracite and bituminous coals. **011 Anthracite** A high-rank, hard coal with a gross calorific value (moist, ash-free basis) greater than or equal to 24 MJ/kg and a vitrinite mean random reflectance greater than or equal to 2.0 per cent. Remark: Anthracite usually has less than 10 per cent volatile matter, a high carbon content (about 86–98 per cent carbon) and is non-agglomerating. It is mainly used for industrial and household heat raising. **012 Bituminous coal** A medium-rank hard coal with either a gross calorific value (moist, ash-free basis) not less than 24 MJ/kg and with a vitrinite mean random reflectance less than 2.0 per cent, or a gross calorific value (moist, ash-free basis) less than 24 MJ/kg provided that the vitrinite mean random reflectance is equal to or greater than 0.6 per cent. Remark: Bituminous coals are agglomerating and have a higher volatile matter and lower carbon content than anthracite. They are used for industrial coking and heat raising and household heat raising. **0121 Coking coal** Bituminous coal that can be used in the production of a coke capable of supporting a blast furnace charge. **0122 Other bituminous coal** This class includes bituminous coal not included under coking coal. Remark: This is sometimes referred to as steam coal. **02 Brown coal** Coals with a gross calorific value (moist, ash-free basis) less than 24 MJ/kg and a vitrinite mean random reflectance less than 0.6 per cent. Remark: Brown coal comprises sub-bituminous coal and lignite. **021 Sub-bituminous coal** Brown coal with a gross calorific value (moist, ash-free basis) equal to or greater than 20 MJ/kg but less than 24 MJ/kg. **022 Lignite** Brown coal with a gross calorific value (moist, ash-free basis) less than 20 MJ/kg. **03 Coal products** This division includes products derived directly or indirectly from the various classes of coal by carbonization or pyrolysis processes, or by the aggregation of finely divided coal or by chemical reactions with oxidising agents, including water. **031 Coal coke** This group includes the solid, cellular, infusible material remaining after the carbonization of certain coals. Remark: Various cokes are defined according to the type of coal carbonized and their conditions of carbonization or use: coke oven coke, gas coke, coke breeze and semi cokes. **0311 Coke oven coke** The solid product obtained from carbonization of coking coal at high temperature. Remark: Coke oven coke is low in moisture, and volatile matter and has the mechanical strength to support a blast furnace charge. It is used mainly in the iron and steel industry acting as heat source and chemical agent. **0312 Gas coke** A by-product from the carbonization of bituminous coal for the manufacture of gas works gas. Remark: Gas coke is used mainly for heating purposes. **0313 Coke breeze** Coke breeze comprises particles of coke of sizes less than 10 mm. Remark: Coke breeze is the residue from screening coke. The coke that is screened may be made from bituminous or brown coals. **0314 Semi cokes** Consists of cokes produced by low temperature carbonization. Remark: Note that semi cokes may be made from bituminous and brown coals and are used as a heating fuel. **032 Patent fuel** A composition fuel made by moulding hard coal fines into briquette shapes with the addition of a binding agent. Remark: Sometimes referred to as hard coal briquettes. **033 Brown coal briquettes (BKB)** A composition fuel made of brown coal produced by briquetting under high pressure with or without the addition of a binding agent. Remark: Either sub-bituminous coal or lignite may be used, including dried lignite fines and dust. **034 Coal tar** The liquid by-product of the carbonization of coal in coke ovens. Remark: Coal tar may be separated by distillation into several liquid products that may be used for pharmaceutical or wood preservative purposes. **035 Coke oven gas** A gas produced from coke ovens during the manufacture of coke oven coke. **036 Gas works gas (and other manufactured gases for distribution)** This group includes gases obtained from the carbonization or gasification of carbonaceous material of fossil or biomass origins in gas works. The gases comprise: (a) gases obtained from carbonization or gasification of coals, cokes, biomass or waste; and (b) substitute natural gas (a methane-rich gas) made from synthesis gas. Remark: Synthesis gas is a mixture of mainly hydrogen and carbon monoxide obtained by cracking hydrocarbons with high temperature steam. The hydrocarbons may be taken from fossil fuels, biofuels or wastes. **037 Recovered gases** Combustible gases of solid carbonaceous origin recovered from manufacturing and chemical processes of which the principal purpose is other than the production of fuel. This includes gases containing carbon monoxide resulting from the partial oxidation of (a) carbon present as coke acting as a reductant in the process, (b) carbon anodes, or (c) carbon dissolved in iron. Remark: Recovered gases may also be referred to as waste or off gases. **0371 Blast furnace gas** The by-product gas of blast furnace operation consisting mainly of nitrogen, carbon dioxide and carbon monoxide. Remark: The gas is recovered as it leaves the furnace. Its calorific value arises mainly from the carbon monoxide produced by the partial combustion of coke and other carbon bearing products in the blast furnace. It is used to heat blast air and as a fuel in the iron and steel industry. It may also be used by other nearby industrial plants. Note that where carbonized biomass (e.g., charcoal or animal meal) is used in blast furnaces, part of the carbon supply may be considered renewable. **0372 Basic oxygen steel furnace gas** The by-product gas of the production of steel in a basic oxygen furnace. The gas is recovered as it leaves the furnace. Remark: The concentration of carbon monoxide in this gas is higher than that in blast furnace gas. The gas is also known as converter gas, LD gas or BOSF gas. **0373 Other recovered gases** Combustible gases of solid carbonaceous origin recovered from manufacturing and chemical processes not elsewhere defined. Remark: Examples of fuel gas production from metals and chemicals processing are in the production of zinc, tin, lead, ferroalloys, phosphorus and silicon carbide. **039 Other coal products** This group includes coal products not elsewhere classified in section 0. **1 Peat and peat products** This section comprises peat, a solid formed from the partial decomposition of dead vegetation under conditions of high humidity and limited air access (initial stage of coalification) and any products derived from it. **11 Peat** A solid formed from the partial decomposition of dead vegetation under conditions of high humidity and limited air access (initial stage of coalification). It is available in two forms for use as a fuel: sod peat and milled peat. Remark: Milled peat is also made into briquettes for fuel use. Peat is not considered a renewable resource as its regeneration period is long. **111 Sod peat** Slabs of peat, cut by hand or machine, and dried in the air. **112 Milled peat** Granulated peat produced by special machines. Remark: Milled peat is used in power stations or for briquette manufacture. **12 Peat products** This division includes products such as peat briquettes derived directly or indirectly from sod peat and milled peat. **121 Peat briquettes** A fuel comprising of small blocks of dried, highly compressed peat made without a binding agent. Remark: Used mainly as a household fuel. **129 Other peat products** Peat products not elsewhere specified such as peat pellets. **2 Oil shale/oil sands** A sedimentary rock that contains organic matter in the form of kerogen. Kerogen is a waxy hydrocarbon-rich material regarded as a precursor of petroleum. Remark: Oil shale may be burned directly or processed by heating to extract shale oil. While oil shale is classified here, the oils extracted from oil shale and oil sands are included in SIEC division 45 (Other hydrocarbons). **3 Natural gas** A mixture of gaseous hydrocarbons, primarily methane, but generally also including ethane, propane and higher hydrocarbons in much smaller amounts and some non-combustible gases such as nitrogen and carbon dioxide. Remark: The majority of natural gas is separated from both non-associated gas originating from fields producing hydrocarbons only in gaseous form, and associated gas produced in association with crude oil. The separation process produces natural gas by removing or reducing the hydrocarbons other than methane to levels that are acceptable in the marketable gas. The natural gas liquids (NGL) removed in the process are distributed separately. Natural gas also includes methane recovered from coal mines (colliery gas) or from coal seams (coal seam gas) and shale gas. When distributed it may also contain methane from anaerobic fermentation or the methanation of biomass. Natural gas may be liquefied (LNG) by reducing its temperature in order to simplify storage and transportation when production sites are remote from centers of consumption and pipeline transportation is not economically practicable. **4 Oil** Liquid hydrocarbons of fossil origins comprising (i) crude oil; (ii) liquids extracted from natural gas (NGL); (iii) fully or partly processed products from the refining of crude oil, and (iv) functionally similar liquid hydrocarbons and organic chemicals from vegetal or animal origins. **41 Conventional crude oil** A mineral oil of fossil origin extracted by conventional means from underground reservoirs, and comprising liquid or near-liquid hydrocarbons and associated impurities such as sulphur and metals. Remark: Conventional crude oil exists in the liquid phase under normal surface temperature and pressure, and usually flows to the surface under the pressure of the reservoir. This is termed conventional extraction. Crude oil includes condensate from condensate fields and field or lease condensate extracted with the crude oil. The various crude oils may be classified according to their sulphur content (sweet or sour) and API gravity (heavy or light). There are no rigorous specifications for the classifications, but a heavy crude oil may be assumed to have an API gravity of less than 20° and a sweet crude oil may be assumed to have less than 0.5 per cent sulphur content. **42 Natural gas liquids (NGL)** Natural gas liquids are a mixture of ethane, propane, butane (normal and iso), (iso)pentane and a few higher alkanes collectively referred to as pentanes plus. Remark: NGL are produced in association with oil or natural gas. They are removed in field facilities or gas separation plants before sale of the gas. All of the components of NGL except ethane are either liquid at the surface or are liquefied for disposal. The definition given above is the most commonly used. However, there is some use of terms based on the vapour pressure of the components that are liquid at the surface or can be easily liquefied. The three resulting groups are in order of increasing vapour pressure: condensates, natural gasoline and liquefied petroleum gas. NGL may be distilled with crude oil in refineries, blended with refined oil products or used directly. NGL differs from LNG (liquefied natural gas), which is obtained by liquefying natural gas from which the NGL has been removed. **43 Refinery feedstocks** This division includes refinery feedstocks, i.e. oils or gases from crude oil refining or the processing of hydrocarbons in the petrochemical industry that are destined for further processing in the refinery excluding blending. Typical feedstocks include naphthas, middle distillates, pyrolysis gasoline and heavy oils from vacuum distillation and petrochemical plants. **44 Additives and oxygenates** Compounds added to or blended with oil products to modify their properties (octane, cetane, cold properties, etc.). Remark: Examples are: (a) oxygenates such as alcohols (methanol, ethanol) and ethers MTBE (methyl tertiary butyl ether), ETBE (ethyl tertiary butyl ether), TAME (tertiary amyl methyl ether); (b) esters (e.g., rapeseed or dimethylester, etc.); and (c) chemical compounds (such as TML (tetra methyl lead), TEL (tetra ethyl lead) and detergents). Some additives/oxygenates may be derived from biomass while others may be of fossil hydrocarbon origin. **45 Other hydrocarbons** This division includes non-conventional oils and hydrogen. Non-conventional oils refer to oils obtained by non-conventional production techniques, that is, oils extracted from reservoirs containing extra heavy oils or oil sands that need heating or treatment (e.g., emulsification) in situ before they can be brought to the surface for refining/processing. They also include oils extracted from oil sands, extra heavy oils, coal and oil shale that are at, or can be brought to, the surface without treatment and require processing after mining (ex situ processing). Non-conventional oils may also be produced from natural gas. Remark: The oils may be divided into two groups: (i) oils for transformation (e.g., synthetic crudes extracted from extra heavy oils, oil sands, coal and oil shale); and (ii) oils for direct use (e.g., emulsified oils, such as orimulsion and gas-to-liquid (GTL) liquids). Oil sands are also known as tar sands. Extra heavy oils are also known as bitumen. This is not the oil product of the same name made from vacuum distillation residue. Although not a hydrocarbon, hydrogen is included here unless it is a component of another gas. **46 Oil products** Products obtained from crude oil, non-conventional oils or gases from oil and gas fields. They may be produced through the refining of conventional crude and non-conventional oils or during the separation of natural gas from gases extracted from oil or gas fields. **461 Refinery gas** Includes a mixture of non-condensable gases, mainly consisting of hydrogen, methane, ethane and olefins obtained during distillation of crude oil or treatment of oil products (e.g., cracking) in refineries or from nearby petrochemical plants. Remark: It is used mainly as a fuel within the refinery. **462 Ethane** A naturally gaseous straight-chain hydrocarbon (C2H6). Remark: Ethane is obtained at gas separation plants or from the refining of crude oil. It is a valuable feedstock for petrochemical manufacture. **463 Liquefied petroleum gases (LPG)** LPG refers to liquefied propane (C3H8) and butane (C4H10) or mixtures of both. Commercial grades are usually mixtures of the gases with small amounts of propylene, butylene, isobutene and isobutylene stored under pressure in containers. Remark: The mixture of propane and butane used varies according to purpose and season of the year. The gases may be extracted from natural gas at gas separation plants or at plants regasifying imported liquefied natural gas. They are also obtained during the refining of crude oil. LPG may be used for heating and as a vehicle fuel. See also the definition for natural gas liquids. Certain oil field practices also use the term LPG to describe the high vapour pressure components of natural gas liquids. **464 Naphtha** Light or medium oils distilling between 30°C and 210°C that do not meet the specification for motor gasoline. Remark: Different naphthas are distinguished by their density and the content of paraffins, isoparaffins, olefins, naphthenes and aromatics. The main uses for naphthas are as feedstock for high-octane gasolines and the manufacture of olefins in the petrochemical industry. **465 Gasolines** Complex mixtures of volatile hydrocarbons distilling between approximately 25°C and 220°C and consisting of compounds in the C4 to C12 range. Remark: Gasolines may contain blending components of biomass origin, especially oxygenates (mainly ethers and alcohols), and additives may be used to boost certain performance features. **4651 Aviation gasoline** Gasoline prepared especially for aviation piston engines with additives that assure performance under flight conditions. Aviation gasolines are predominantly alkylates (obtained by combining C4 and C5 isoparaffins with C3, C4 and C5 olefins) with the possible addition of more aromatic components including toluene. The distillation range is 25°C to 170°C. **4652 Motor gasoline** A mixture of some aromatics (e.g., benzene and toluene) and aliphatic hydrocarbons in the C5 to C12 range. The distillation range is 25°C to 220°C. Remark: Additives are blended to improve octane rating, improve combustion performance, reduce oxidation during storage, maintain cleanliness of the engine and improve capture of pollutants by catalytic converters in the exhaust system. Motor gasoline may also contain biogasoline products when blended. **4653 Gasoline-type jet fuel** Light hydrocarbons for use in aviation turbine power units, distilling between 100°C and 250°C. They are obtained by blending kerosene and gasoline or naphtha in such a way that the aromatic content does not exceed 25 per cent in volume, and the vapour pressure is between 13.7 kPa and 20.6 kPa. Remark: Gasoline-type jet fuel is also known as aviation turbine fuel. **466 Kerosenes** Mixtures of hydrocarbons in the range C9 to C16 and distilling over the temperature interval 145°C to 300°C, but not usually above 250°C and with a flash point above 38°C. Remark: The chemical compositions of kerosenes depend on the nature of the crude oils from which they are derived and the refinery processes that they have undergone. Kerosenes obtained from crude oil by atmospheric distillation are known as straight-run kerosenes. Such streams may be treated by a variety of processes to produce kerosenes that are acceptable for blending as jet fuels. Kerosenes are primarily used as jet fuels. They are also used as domestic heating and cooking fuels, and as solvents. Kerosenes may include components or additives derived from biomass when blended. **4661 Kerosene-type jet fuel** A blend of kerosenes suited to flight conditions with particular specifications, such as freezing point. Remark: The specifications are set down by a small number of national standards committees, most notably ASTM (United States of America), MOD (United Kingdom of Great Britain and Northern Ireland), GOST (Russia). **4669 Other kerosene** Kerosene that is used for heating, cooking, lighting, solvents and internal combustion engines. Remark: Other names for this product are burning oil, vaporizing oil, power kerosene and illuminating oil. **467 Gas oil/diesel oil and heavy gas oil** This group includes gas oils and heavy gas oils. **4671 Gas oil/diesel oil** Gas oils are middle distillates, predominantly of carbon number range C11 to C25 and with a distillation range of 160°C to 420°C. Remark: The principal marketed products are fuels for diesel engines (diesel oil), heating oils and marine fuel. Gas oils are also used as middle distillate feedstock for the petrochemical industry and as solvents. **4672 Heavy gas oil** A mixture of predominantly gas oil and fuel oil that distills in the range of approximately 380°C to 540°C. **468 Fuel oil** Comprises residual fuel oil and heavy fuel oil. Residual fuel oils have a distillation range of 350°C to 650°C and a kinematic viscosity in the range 6 to 55 cSt at 100°C. Their flash point is always above 60°C and their specific gravity is above 0.95. Heavy fuel oil is a general term describing a blended product based on the residues from various refinery processes. Remark: Other names commonly used to describe fuel oil include: bunker fuel, bunker C, fuel oil No. 6, industrial fuel oil, marine fuel oil and black oil. Residual and heavy fuel oil are used in medium to large industrial plants, marine applications and power stations in combustion equipment such as boilers, furnaces and diesel engines. Residual fuel oil is also used as fuel within the refinery. **469 Other oil products** This group includes oil products not covered in groups 461–468. **4691 White spirit and special boiling point industrial spirits** White spirit and special boiling point (SBP) industrial spirits are refined distillate intermediates with a distillation in the naphtha/kerosene range. They are mainly used for non-fuel purposes and sub-divided as: (a) white spirit—an industrial spirit with a flash point above 30°C and a distillation range of 135°C to 200°C; and (b) industrial spirit (SBP)—light oils distilling between 30°C and 200°C. Remark: There are seven or eight grades of industrial spirits, depending on the position of the cut in the distillation range. The grades are defined according to the temperature difference between the 5 per cent and 90 per cent volume distillation points (which is not more than 60°C). White spirit and industrial spirits are mostly used as thinners and solvents. **4692 Lubricants** Oils, produced from crude oil, for which the principal use is to reduce friction between sliding surfaces and during metal cutting operations. Remark: Lubricant base stocks are obtained from vacuum distillates that result from further distillation of the residue from atmospheric distillation of crude oil. The lubricant base stocks are then further processed to produce lubricants with the desired properties. **4693 Paraffin waxes** Residues extracted when dewaxing lubricant oils. The waxes have a crystalline structure that varies in fineness according to the grade, and are colourless, odourless and translucent, with a melting point above 45°C. Remark: Paraffin waxes are also known as petroleum waxes. **4694 Petroleum coke** Petroleum coke is a black solid obtained mainly by cracking and carbonizing heavy hydrocarbon oils, tars and pitches. It consists mainly of carbon (90 to 95 per cent) and has a low ash content. The two most important categories are green coke and calcined coke. Green coke (raw coke) is the primary solid carbonization product from high boiling hydrocarbon fractions obtained at temperatures below 630°C. It contains 4–15 per cent by weight of matter that can be released as volatiles during subsequent heat treatment at temperatures up to approximately 1330°C. Calcined coke is a petroleum coke or coal-derived pitch coke obtained by heat treatment of green coke to about 1330°C. It will normally have a hydrogen content of less than 0.1 per cent by weight. Remark: In many catalytic operations (e.g., catalytic cracking) carbon or catalytic coke is deposited on the catalyst, thus deactivating it. The catalyst is reactivated by burning off the coke that is used as a fuel in the refining process. The coke is not recoverable in a concentrated form. **4695 Bitumen** A solid, semi-solid or viscous hydrocarbon with a colloidal structure, being brown to black in color. Remark: Bitumen is obtained as a residue in the distillation of crude oil and by vacuum distillation of oil residues from atmospheric distillation. It should not be confused with the non-conventional primary extra heavy oils that may also be referred to as bitumen. In addition to its major use for road pavements, bitumen is also used as an adhesive, a waterproofing agent for roof coverings and as a binder in the manufacture of patent fuel. It may also be used for electricity generation in specially designed power plants. Bitumen is also known in some countries as asphalt, but in others asphalt describes the mixture of bitumen and stone aggregate used for road pavements. **4699 Other oil products n.e.c.** Products (including partly refined products) from the refining of crude oil and feedstocks that are not specified above. Remark: These products will include basic chemicals and organic chemicals destined for use within the refinery or for sale to or processing in the chemical industry such as propylene, benzene, toluene and xylene. **5 Biofuels** Fuels derived directly or indirectly from biomass. Remark: Fuels produced from animal fats, by-products and residues obtain their calorific value indirectly from the plants eaten by the animals. **51 Solid biofuels** Solid fuels derived from biomass. **511 Fuelwood, wood residues and by-products** Fuelwood or firewood (in log, brushwood, pellet or chip form) obtained from natural or managed forests or isolated trees. Also included are wood residues used as fuel and in which the original composition of wood is retained. Remark: Charcoal and black liquor are excluded. **5111 Wood pellets** Wood pellets are a cylindrical product that has been agglomerated from wood residues by compression with or without the addition of a small quantity of binder. The pellets have a diameter not exceeding 25 mm and a length not exceeding 45 mm. **5119 Other Fuelwood, wood residues and by-products** This class includes fuelwood, wood residues and by-products, except in the form of wood pellets. **512 Bagasse** The fuel obtained from the fibre that remains after juice extraction in sugar cane processing. **513 Animal waste** Excreta of animals, meat and fish residues that, when dry, are used directly as a fuel. Remark: This excludes waste used in anaerobic fermentation plants. Fuel gases from these plants are included under biogases. **514 Black liquor** The alkaline-spent liquor obtained from the digesters during the production of sulphate or soda pulp required for paper manufacture. Remark: The lignin contained in the liquor burns to release heat when the concentrated liquor is sprayed into a recovery furnace and heated with hot gases at 900°C. Black liquor is used as a fuel in the pulping process. **515 Other vegetal material and residues** Solid primary biofuels not specified elsewhere, including straw, vegetable husks, ground nut shells, pruning brushwood, olive pomace and other wastes arising from the maintenance, cropping and processing of plants. **516 Charcoal** The solid residue from the carbonization of wood or other vegetal matter through slow pyrolysis. **52 Liquid biofuels** Liquids derived from biomass and used as fuels. Remark: Liquid biofuels comprise biogasoline, biodiesels, bio jet kerosene and other liquid biofuels. They are used for transport, electricity generation and stationary engines. **521 Biogasoline** Liquid fuels derived from biomass and used in spark-ignition internal combustion engines. Remark: Common examples are: bioethanol (including both hydrous and anhydrous ethanol); biomethanol; biobutanol; bio ETBE (ethyl-tertio-butyl-ether); and bio MTBE (methyl-tertio-butyl-ether). Biogasoline may be blended with petroleum gasoline or used directly in engines. The blending may take place in refineries or at or near the point of sale. **522 Biodiesels** Liquid biofuels derived from biomass and used in diesel engines. Remark: Biodiesels obtained by chemical modification are a linear alkyl ester made by transesterification of vegetable oils or animal fats with methanol. The transesterification distinguishes biodiesel from straight vegetable and waste oils. Biodiesel has a flash point of around 150°C and a density of about 0.88 kg/litre. Biological sources of biodiesel include, but are not limited to, vegetable oils made from canola (rapeseed), soybeans, corn, oil palm, peanut or sunflower. Some liquid biofuels (straight vegetable oils) may be used without chemical modification and their use usually requires modification of the engine. A further category of diesel fuels can be produced by a range of thermal processes (including for example gasification followed by Fischer-Tropsch synthesis, pyrolysis followed by hydrogenation, or conversion of sugar to hydrocarbons using microorganisms (e.g. yeast)). A wide range of biomass feedstocks, including cellulosic materials and algal biomass, could be used in such processes. Biodiesels may be blended with petroleum diesel or used directly in diesel engines. **523 Bio jet kerosene** Liquid biofuels derived from biomass and blended with or replacing jet kerosene. Remark: Bio jet kerosene can be produced by a range of thermal processes, including for example gasification followed by Fischer-Tropsch synthesis, pyrolysis followed by hydrogenation, or conversion of sugar to hydrocarbons using microorganisms (e.g. yeast). A wide range of biomass feedstocks, including cellulosic materials and algal biomass could be used in such processes. **529 Other liquid biofuels** This group includes liquid biofuels not elsewhere specified. **53 Biogases** Gases arising from the anaerobic fermentation of biomass and the gasification of solid biomass (including biomass in wastes). Remark: The biogases from anaerobic fermentation are composed principally of methane and carbon dioxide and comprise landfill gas, sewage sludge gas and other biogases from anaerobic fermentation. Biogases can also be produced from thermal processes (by gasification or pyrolysis) of biomass and are mixtures containing hydrogen and carbon monoxide (usually known as syngas) along with other components. These gases may be further processed to modify their composition and can be further processed to produce substitute natural gas. The gases are divided into two groups according to their production: biogases from anaerobic fermentation; and biogases from thermal processes. They are used mainly as a fuel but can be used as a chemical feedstock. **531 Biogases from anaerobic fermentation** The biogases from anaerobic fermentation are composed principally of methane and carbon dioxide and comprise landfill gas, sewage sludge gas and other biogases from anaerobic fermentation. Explanation: The biogases from anaerobic fermentation are composed principally of methane and carbon dioxide and include gas produced from a range of wastes and other biomass materials, including energy crops in anaerobic digesters (including sewage sludge gas and landfill gas). The gases may be processed to remove the carbon dioxide and other constituents to produce a methane fuel. **5311 Landfill gas** Biogas from the anaerobic fermentation of organic matter in landfills. **5312 Sewage sludge gas** Biogas from the anaerobic fermentation of waste matter in sewage plants. **5319 Other biogases from anaerobic fermentation** Other biogases from anaerobic fermentation not elsewhere specified. Remark: Two of the largest sources of these biogases are the fermentation of energy crops and the fermentation of manure on farms. **532 Biogases from thermal processes** Biogases from thermal processes (by gasification or pyrolysis) of biomass. Remark: Biogases from thermal processes are a mixture containing hydrogen and carbon monoxide (usually known as syngas) along with other components. These gases may be further processed to modify their composition and can be further processed to produce substitute natural gas. **6 Waste** This section includes waste, i.e. materials no longer required by their holders. Remark: For the purposes of energy statistics, waste refers to the part of these materials that is incinerated with heat recovery at installations designed for mixed wastes or co-fired with other fuels. The heat may be used for heating or electricity generation. Certain wastes are mixtures of materials of fossil and biomass origin. **61 Industrial waste** Non-renewable waste that is combusted with heat recovery in plants other than those used for the incineration of municipal waste. Remark: Examples are used tires, specific residues from the chemical industry and hazardous wastes from health care. Combustion includes co-firing with other fuels. The renewable portions of industrial waste combusted with heat recovery are classified according to the biofuels that best describe them. **62 Municipal waste** Household waste and waste from companies and public services that resembles household waste and which is collected at installations specifically designed for the disposal of mixed waste, with recovery of combustible liquids, gases or heat. Remark: Municipal waste can be divided into renewable and non-renewable fractions. **7 Electricity** This section includes electricity, i.e. the transfer of energy through the physical phenomena involving electric charges and their effects when at rest and in motion. Remark: Electricity can be generated through different processes such as the conversion of energy contained in falling or streaming water, wind or waves; the direct conversion of solar radiation through photovoltaic processes in semiconductor devices (solar cells); or by the combustion of fuels. **8 Heat** This section includes heat, i.e. the energy obtained from the translational, rotational and vibrational motion of the constituents of matter, as well as changes in its physical state. Remark: Heat can be produced by different production processes. **9 Nuclear fuels and other fuels n.e.c.** This section includes nuclear fuels, including uranium, thorium, plutonium and derived products that can be used in nuclear reactors as a source of electricity and/or heat, as well as fuels not elsewhere classified. **91 Uranium and plutonium** This division includes uranium ores and concentrates; natural uranium, uranium enriched in U 235, plutonium and their compounds; alloys, dispersions (including cermets), ceramic products and mixtures containing natural uranium, uranium enriched in U 235, plutonium or compounds of these products; as well as fuel elements (cartridges) of nuclear reactors (non-irradiated or irradiated). **9101 Uranium ores** This class includes uranium ores and concentrates. **9109 Other uranium and plutonium** This class includes natural uranium, uranium enriched in U 235, plutonium and their compounds; alloys, dispersions (including cermets), ceramic products and mixtures containing natural uranium, uranium enriched in U 235, plutonium or compounds of these products; as well as fuel elements (cartridges) of nuclear reactors (non-irradiated or irradiated). **92 Other nuclear fuels** This division includes thorium and its compounds; alloys, dispersions (including cermets), ceramic products and mixtures containing thorium or compounds of thereof; other radioactive elements and isotopes and compounds (other than uranium, thorium or plutonium); alloys, dispersions (including cermets), ceramic products and mixtures containing these elements, isotopes or compounds. **99 Other fuels n.e.c.** This division includes fuels not elsewhere classified. --- [^17]: In table 3.1, this is indicated with an asterisk next to the relevant link. [^18]: SIEC does not cover underground deposits of energy resources, i.e. "non-renewable energy resources of both inorganic and organic origin discovered in the earth's crust in solid, liquid and gaseous form". A classification of underground mineral and energy resources is expected to be provided in the forthcoming SEEA-Energy (as part of the general SEEA classification of "natural resources"), based on the definitions and classification of the United Nations Framework Classification for Fossil Energy and Mineral Reserves and Resources (UNFC). [^19]: The term fuel refers to energy sources, whether primary or secondary, that must be subjected to combustion or fission in order to release for use the energy stored up in them. [^20]: For the purposes of the discussion on the scope of SIEC, fossil fuels refer to coal, peat, oil and natural gas, even though the inclusion of peat in fossil fuels is not universally accepted. [^21]: Although, strictly speaking, part of waste can have a fossil origin, this part has already been accounted for as used (often for non-energy purposes), thus it is treated together with other fuels of non-fossil origin to avoid imbalances in the energy flows. [^22]: In some cases, demands for energy statistics require a different treatment for energy products. One such example would be the classification of certain chemical compounds as individual oil products in terms of production, but as refinery feedstocks in terms of inputs used. However, in both applications the treatment is unambiguous and the energy balances include a mechanism to match these different flows. See also para. 3.14. [^23]: The definitions for nuclear fuel are not in the scope of products discussed by InterEnerStat and have instead been provided by the International Atomic Energy Agency (IAEA).