Biomass is all plant and animal matter on the Earth's surface.
Biomass is anything that is alive. It is also anything that was
alive a short time ago. In the context of biomass for energy this
is often used to mean plant based material, but biomass can equally
apply to both animal and vegetable derived material.
The carbon used to construct biomass is absorbed from the
atmosphere as carbon dioxide (CO2) by
plant life, using energy from the sun. Plants may subsequently be
eaten by animals and thus converted into animal biomass. However
the primary absorption is performed by plants. If plant material is
not eaten it is generally either broken down by micro-organisms or
burned: If broken down it releases the carbon back to the
atmosphere, mainly as either carbon dioxide (CO2) or methane. If burned the carbon is returned
to the atmosphere as CO2. These processes
have happened for as long as there have been plants on Earth and is
part of what is known as the carbon cycle.
If it is managed on a sustainable basis, biomass is harvested as
part of a constantly replenished crop. This is either during
woodland or arboricultural management or coppicing or as part of a
continuous programme of replanting with the new growth taking up
CO2 from the atmosphere at the same time
as it is released by combustion of the previous harvest.
Within this definition, biomass for energy can include a wide
range of materials.
There are five basic categories of material:
Biomass is a renewable, low carbon fuel that is already widely,
and often economically available throughout the UK. Its production
and use also brings additional environmental and social benefits.
Correctly managed, biomass is a sustainable fuel that can deliver a
significant reduction in net carbon emissions when compared with
Burning any carbon-based fuel converts carbon to carbon dioxide.
Unless it is captured and stored, this carbon dioxide is usually
released to the atmosphere. Burning fossil fuels releases carbon
that was removed from the atmosphere millions of years ago by
animal and plant life. This leads to increased concentrations of
carbon dioxide in the atmosphere.
The greenhouse effect is the heating of the surface of earth due
to the presence of an atmosphere containing gases that absorb and
emit infrared radiation.
Greenhouse gases, which include carbon dioxide, water vapor and
methane, are almost transparent to solar radiation but strongly
absorb and emit infrared radiation. Thus, greenhouse gases trap
heat within the surface-troposphere system
The increasing concentrations of greenhouse gases in the
atmosphere since the industrial revolution and the resulting
widespread use of fossil fuels, gives rise to an increase in the
greenhouse effect, and an increase in the average global
temperature, known as Global Warming. This is predicted to lead to
widespread, unpredictable changes to the global climate.
The combustion (direct or indirect) of biomass as a fuel also
returns CO2 to the atmosphere. However this carbon is part of the
current carbon cycle: it was absorbed during the growth of the
plant over the previous few months or years and, provided the land
continues to support growing plant material, a sustainable balance
is maintained between carbon emitted and absorbed.
The amount of additional biomass that grows over the course of a
year in a given area is known as the annual increment. Provided the
amount consumed is less than the annual increment its use can be
sustainable and biomass can be considered a low carbon fuel and
biomass CO2 absorption and emission is in balance.
Source: The Biomass Energy Centre UK: www.biomassenergycentre.org.uk