Technical Notes: Energy Production by Source VARIABLE DEFINITIONS AND METHODOLOGY: Energy Production is the production of primary energy that is extracted from the ambient environment. In addition to solid, liquid, and gaseous fuels and nuclear electricity, the total also includes hydropower, geothermal, solar, combustible renewables and waste, and indigenous heat production from heat pumps. These data show the amount of electricity and heat produced specifically for human consumption. Production is measured in a common unit of 1,000 metric tons of oil equivalent (toe). One metric toe is equal to the net heat content of a metric ton of crude oil and can also be expressed as 10 Exp. 7 kilocalories (equivalent to a food calorie) or 41.868 gigajoules. Total From All Sources is total production from all energy sources including fossil fuels, nuclear electricity, hydroelectric plants, modern renewables, and renewable fuels and wastes. Per capita values are calculated by the World Resources Institute as the amount of energy (in kilograms of oil equivalent) produced per person, regardless of source. Population data are from the United Nations Population Division. Energy production data are from the IEA. Solid Fuels shows the energy produced by coal and all coal products, such as peat and coke. Liquid Fuels shows the energy produced by crude oil or natural gas liquids. These include motor and aviation gasoline, kerosene, diesel oil, and petrochemical feedstocks, which refer to all oil products used as raw material in the petrochemical industry for steamcracking, aromatics plants. e.g. naphtha, liquefied petroleum gases, light and heavy gasoil, reformate, etc. Gaseous Fuels shows the amount of energy produced by natural gases, occurring in underground deposits, whether liquefied or gaseous, consisting mainly of methane. Gaseous Fuels include "non- associated" gas from fields producing gaseous hydrocarbons, and "associated" gas produced in association with crude oil, and methane recovered from coal mines (colliery gas). Nuclear energy production shows the primary heat equivalent of the electricity produced by nuclear power plants. Heat-to-electricity conversion efficiency is assumed to be 33 percent. Hydroelectric refers to the energy content of the electricity produced in hydroelectric power plants, which convert the potential and kinetic energy of water into electricity. This variable excludes output from pumped storage. Other Renewables shows the amount of energy produced by renewable sources such as wind; tide, wave and ocean; thermal and photovoltaic solar; primary solid biomass from plant matter; liquid biomass fuels such as ethanol; biogas from digesters; and geothermal systems. The energy production values presented here are calculated by the International Energy Agency (IEA). Their energy balance methodology is based on the calorific content of energy commodities, measured in a common unit of account known as the metric ton of oil equivalent (toe). This quantity of energy, defined as 10 Exp. 7 kilocalories or 41.868 gigajoules, is equal to the net heat content of 1 metric ton of crude oil. To account for the differences in quality between types of coal and other energy sources, the IEA has applied specific conversion factors supplied by national administrations for the main categories of energy sources and flows or uses (i.e. production, imports, exports, industry). Energy statistics are expressed in terms of net calorific value and therefore may be slightly lower than statistics presented elsewhere using gross calorific value. For oil and coal, net calorific value is 5 percent less than gross; for most forms of natural and manufactured gas, the difference is 9-10 percent. Using net calorific values is consistent with the United Nations and European Community statistical offices. When calculating the primary energy equivalent for sources such as nuclear, geothermal, solar, hydro, wind, etc., the IEA uses the physical energy content of the source's primary energy form. The IEA assumes that a source's primary energy form is the first energy form for which multiple energy uses are practical. In the case of nuclear energy, for instance, the quantity of heat generated in the reactors, rather than the energy content of the nuclear fuel, is reported as the primary energy form. Heat is also the chosen form for geothermal heat and electricity production, and solar heat production. Electricity is the chosen form for hydro, wind, wave/ocean and photovoltaic solar electricity production. The IEA has two primary methods of obtaining data. Firstly, the IEA sends out 5 annual questionnaires to each OECD member country to collect energy data for the preceding two years. The questionnaires address each of the following subjects: crude oil and petroleum products; natural gas; electricity and heat; solid fuels and manufacture gases; and renewables and wastes. The IEA gathers further data through its Monthly Oil Statistics questionnaires and various mini-questionnaires. Data for non-OECD countries are collected by way of other international organizations, i.e. United Nations, OLADE; close cooperation with national statistical bodies; direct contacts with energy consultants and companies; publications; and questionnaires for UN-ECE countries (identical to those sent to OECD member countries). FREQUENCY OF UPDATE BY DATA PROVIDERS: IEA updates their energy data annually. The UN Population Division updates the figures used for per capita calculations every other year. These updates also often include revisions of past data. Data may therefore differ from those reported in prior EarthTrends data tables. DATA RELIABILITY AND CAUTIONARY NOTES: Energy: The energy balances data are primarily based on well-established and institutionalized accounting methodologies, and are therefore considered reliable. One exception is the calculation of fuelwood and other biomass fuel use, which are estimated by the IEA based on small sample surveys or other incomplete information. These data give only a broad impression of trends and should not be strictly compared between countries. The IEA also reports that it can be difficult to distinguish between agriculture, commercial, and public sectors, and there may be some overlap in these sectors. IEA data do not distinguish between no data (denoted in these tables with X) and zero values. WRI has distinguished between the two where possible, but some values represented as zero should probably be indicated by X and vice versa. Extreme caution should be exercised if considering using the data to extrapolate into the future. Energy usage is extremely variable from year to year due to short-term factors such as the weather and the economy that significantly impact any one year's production. Population (per capita calculations): United Nations demographic models are based on recent surveys and censuses with well-understood qualities, which make these data fairly reliable, although accuracy varies. Data are adjusted for overenumeration and underenumeration of certain age and sex groups (e.g., infants, female children, and young males), misreporting of age and sex distributions, and changes in definitions, when necessary. These adjustments incorporate data from civil registrations, population surveys, earlier censuses, and, when necessary, population models based on information from socioeconomically similar countries. Historical data are used when deemed accurate, also with adjustments and scaling. However, accurate historical data do not exist for many developing countries. In such cases, the UN Population Division uses available information and demographic models to estimate the main demographic parameters. SOURCES: Energy: International Energy Agency (IEA), 2001. Energy Balances of OECD Countries (2001 Edition) and Energy Balances of non-OECD Countries (2001 Edition). Paris: Organization for Economic Cooperation and Development (OECD). Electronic database available online at: http://data.iea.org/. Population (for per capita calculations): Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat, 2002. World Population Prospects: The 2000 Revision. New York: United Nations. Dataset available on CD-ROM.