Units and Terminology

Data in the wood energy database are given in standard units and terminology. Below, conversion values are given per type of unit. Furthermore, an overview of the terminology used is given in alphabethical order. For more information, see Energy and Environment Basics.

Units

Unit Prefixes
Prefixes are used as multiplication factors for standards units.

Name	Prefix	Factor
Kilo	k	10 E+3
Mega	M	10 E+6
Giga	G	10 E+9
Tera	T	10 E+12
Peta	P	10 E+15

ENERGY	TJ	Ktoe	Ktce	Gwh
Terajoule (TJ)	1	0.024	0.034	0.28
Kiloton oil equivalent (Ktoe)	41.868	1	1.428	11.63
Kiloton coal equivalent (Ktce)	29.308	0.700	1	8.14
Gigawatt-hour (Gwh)	3.6	0.086	0.123	1

AREA	ha	acre	km2
Hectare (ha)	1	2.47	0.01
Acre	0.4	1	0.004
Square kilometer (km2)	100	247	1

Terminology

	Ash content: Refers to the non-combustible materials in a fuel, which reduce the heating value per unit of weight.
	Biomass: All forms of organic matter, including wood, agricultural crops and residues, animal dung and human waste. It can also include biomass products, such as ethanol.
	Briquetting: Densification of loose organic material, such as rice husk, sawdust, coffee husks, to improve fuel characteristics including handling and combustion properties.
	Carbonization: The destructive distillation of organic substances in the absence of air resulting in the removal of volatile constituents and leaving a residue high in carbon, e.g. coke, charcoal.
	Charcoal: Solid residue consisting mainly of carbon obtained by the destructive distillation of wood in the absence of air. Instead of wood, also other forms of biomass are sometimes used, such as coconut shells. Popular cooking fuel in Southeast Asia, but also used by chemical industries.
	Co-generation: Sequential production of both heat and power using the same fuel. An example is the use of expanded steam left over after generating electricity for heating purposes. The concept is increasingly being applied in many wood and agro-processing industries (such as sugar and palm oil mills).
	Combined Heat and Power Generation (CHP): Simultaneous production of both heat and power. The difference with co-generation is that the generation of heat and power may be done as parallel processes, which results in a lower overall efficiency.
	Combustion: Chemical reaction between a fuel and oxygen which usually takes place in air. More commonly known as burning. The products are carbon dioxide and water with the release of heat.
	Commercial energy: Literally, energy traded in the market for a monetary price, usually conventional energy, such as coal or oil, but also wood energy, which is traded in urban and semi-urban areas in many developing countries. Often used to refer to conventional fuels, such as coal, gas and electricity, thus ignoring commercially traded woodfuels. The term non-commercial energy is often used to refer to biomass energy, ignoring the commercial trade of woodfuels and other biomass fuels.
	Conventional energy: Fossil based fuels, such as oil, coal, natural gas and their derivates, for which large-scale mechanism for exploration, conversion and distribution exist.
	Crop residues (or agricultural residues): By-products of the agricultural production system, such as straws, husks, shells stalks and animal dung, with a large number of uses, including energy. Residues can be divided into two groups: field residues, which remain on the field after harvest, for example, cotton stalks; and process residues, generated off-field at a central production site, for example, rice husk.
	Dendro-power: Conversion of wood energy to electricity or shaft power.
	End-use: The user application for which energy is required, for example lighting, cooking, space-heating, drying, milling, sawing.
	Energy balance: Table accounting for all the energy which is produced and consumed for a certain time period in a system, e.g. a country, region, factory or process. The energy balance is used to represent the production, conversion and consumption for all fuels in the system in one table and in one unit.
	Energy content (or heating value): The amount of energy per physical unit, e.g. Joule per Kilogram or Ton of oil equivalent per litre. For combustible fuels (including biomass fuels), this is the amount of energy in the form of heat that is released when the fuel is totally burned. For woodfuels, the heating value can vary widely, due to the density and moisture and ash content of the wood. The density of the wood varies for different wood species, e.g. hard wood has a higher density than softwood, so hard wood has a higher heating value per unit of volume.
	Energy conversion: In physical terms, a process which transforms energy from one form into another, for example, the conversion of wood into heat by combustion. In energy terms, it refers to production processes that transform one fuel into a fuel that can be transported or transmitted, for example electricity generation from coal, or charcoal production from wood.
	Energy efficiency: Conversion ratio of output and input energy of energy production technologies and end-use appliances. The lower the efficiency, the more energy is lost.
	Energy replacement value: The amount of a particular energy form which in practice is needed to do the same job as another energy form or fuel, taking into account the efficiencies of end-use devices.
	Energy Unit: Unit used to express the quantity of heat, energy or work. Common units are the joule (J), ton of oil equivalent (toe), calorie (cal), kilowatt-hour (kwh).
	Final energy: Energy in the form that the consumer buys or receives to perform a desired task with an end-use device.
	Fossil fuels: The non-renewable energy resources of coal, petroleum or natural gas or any fuel derived from them. Exploitation of new reserves has a long development period.
	Fuelwood (or firewood): All wood in the rough used for fuel purposes, including trunks, branches and twigs of trees as well as residues from wood processing industries used as energy source.
	Gasification: Conversion of solid fuels (biomass and coal) at high temperatures in the absence of air to produce combustible gases.
	Moisture content: Quantity of water in a material, expressed as a percentage of the material's weight. Moisture content is the most critical factor determining the amount of useful heat from biomass combustion, because the water is evaporated before heat is available for the application. For freshly cut wood the moisture content is high, for air-dried wood the moisture content has adapted to the humidity of the environment, and for oven-dried wood the moisture content is zero.
	Primary energy: Energy form as it is available in nature.
	Renewable energy: Any form of primary energy, for which the source is not depleted by use. Wind and solar are always renewable, biomass can be renewable if its consumption is matched by the re-growth. Non-renewable energy refers to any form of primary energy, the supply of which is finite and hence its use depletes the existing stock. It generally refers to fossil fuels.
	Secondary energy: Energy after conversion in a form ready for transport or transmission.
	Useful energy: The actual energy required for the end-use, almost always in the form of heat or mechanical shaft power.
	Wood energy (or woodfuel): Refers to all forms of energy derived from wood. For Asia this mainly means fuelwood and charcoal, but it can also refer to modern applications such as dendro-power.
	Woodfuel flows: The distribution and marketing of woodfuels from the production site to end-users.
	Woody biomass: Stems, branches, shrubs, hedges, twigs and residues of wood processing. Non-woody biomass refers to stalks, leaves, grass, animal and human waste.