Short rotation coppice
Encyclopedia
Short Rotation Coppice is coppice
grown as an energy crop
. This woody solid biomass
can be used in applications such as district heating, electric power
generating stations, alone or in combination with other fuels.
varieties of poplar
and willow
. Typically the willow species chosen are varieties of the Common Osier
or Basket Willow, Salix viminalis. Poplar is generally planted for visual variation rather than being a commercial crop, although some varieties can outperform willow on suitable sites.
Species are selected for their acceptance of varying climate and soil conditions, relative insusceptibility to pests and diseases, ease of propagation and speed of vegetative growth. To combat pests such as brassy and blue willow beetle
s, as well as the fungal pathogen Melampsora
(a rust
), planting a carefully selected mix of varieties is recommended. The management of the plantations highly affects the productivity and its success.
the SRC yield may be smaller. Water availability to the roots is a key determinant for the success of the SRC.
Saplings are planted at a high density, around 15,000 per hectare
for willow and 12,000 per hectare for poplar. Planting takes place around March to take advantage of the high moisture of the soil in the spring and the amount of sunshine in the early summer. The most efficient planting machines plant four rows at a time and can plant a hectare in around three hours. Saplings are left to grow for a year and then coppiced.
The primary barrier to establishing plantations is the cost as there is no financial reward for four years from a large initial investment. However, in the UK grants are available to support establishment
When willow or poplar shoots are harvested as whole stems they are easy to store. The stems can be dried for combustion in a pile outdoors; the moisture content of the wood will decrease to about 30% on average until the next autumn. The stems can be cut further into billets that may not need to be chipped depending on use.
Where wood chip is being produced it is most efficient to use direct-chip harvesters. These are heavy self-powered machines that cut and chip the shoots on a loading platform. Some can be attached to a normal tractor and a hectare can be harvested in around 3 hours. Direct chipping reduces costs as a separate chipping in the store will not be needed; however, the wood chip needs to be well stored to avoid it composting. Harvesting Poplar requires heavier machinery as it produces fewer and heavier stems.
The price of dry willow as a heating fuel is currently around 45 euro per tonne in most of Europe. This is not a relatively high-return crop, but it is low-maintenance and is a way of utilising difficult fields. Small scale production can be combined with the production of material for wicker
work. Correctly managed there is little need for pesticides or treatments.
impact as any carbon dioxide released in power generation will have been sequestered by the plantation over just a few years. Some carbon may also be stored in the soil, however the extent of this carbon storage is dependent on the carbon content of the soil to begin with.
The carbon costs associated with SRC are: the planting, farming and chipping of the SRC plantation, generally done with fossil fuel
powered machinery; the crops require herbicides during establishment, fertiliser throughout growth, and occasional pesticide
treatment - these chemicals require substantial amounts of energy and potential fossil fuel usage through manufacture.
Electricity or heat from SRC provides between three and six times the CO2 reduction per pound that can be obtained from bioethanol from cereal crops. However, the reduction in CO2 emissions is slightly lower than grass energy crops such as Miscanthus
grass due to higher maintenance costs.
SRC has a higher water consumption than agricultural crops. The root systems of SRC have a lower impact on archaeological remains than forestry but greater than agricultural crops such as wheat.
Coppicing
Coppicing is a traditional method of woodland management which takes advantage of the fact that many trees make new growth from the stump or roots if cut down. In a coppiced wood, young tree stems are repeatedly cut down to near ground level...
grown as an energy crop
Energy crop
An energy crop is a plant grown as a low cost and low maintenance harvest used to make biofuels, or combusted for its energy content to generate electricity or heat. Energy crops are generally categorized as woody or herbaceous ....
. This woody solid biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
can be used in applications such as district heating, electric power
Electric power
Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt.-Circuits:Electric power, like mechanical power, is represented by the letter P in electrical equations...
generating stations, alone or in combination with other fuels.
Species used
SRC uses high yieldCrop yield
In agriculture, crop yield is not only a measure of the yield of cereal per unit area of land under cultivation, yield is also the seed generation of the plant itself...
varieties of poplar
Poplar
Populus is a genus of 25–35 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar , aspen, and cottonwood....
and willow
Willow
Willows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere...
. Typically the willow species chosen are varieties of the Common Osier
Common Osier
Salix viminalis, the Common Osier or Osier, is a species of willow native to Europe and western Asia.-Description:...
or Basket Willow, Salix viminalis. Poplar is generally planted for visual variation rather than being a commercial crop, although some varieties can outperform willow on suitable sites.
Species are selected for their acceptance of varying climate and soil conditions, relative insusceptibility to pests and diseases, ease of propagation and speed of vegetative growth. To combat pests such as brassy and blue willow beetle
Blue willow beetle
The blue willow beetle is a bronze–black beetle of the family Chrysomelidae. It is found on aspen and various willow species in fens, carrs and on river banks. It is susceptible toBacillus thuringiensis tenebrionis and also Spinosad when treatment is applied to affected plants. Proliferation of...
s, as well as the fungal pathogen Melampsora
Melampsora
Melampsora is a genus of Basidiomycota fungi. Melampsora species are known as plant pathogens.-External links:*...
(a rust
Rust (fungus)
Rusts are plant diseases caused by pathogenic fungi of the order Pucciniales. About 7800 species are known. Rusts can affect a variety of plants; leaves, stems, fruits and seeds. Rust is most commonly seen as coloured powder, composed off tiny aeciospores which land on vegetation producing...
), planting a carefully selected mix of varieties is recommended. The management of the plantations highly affects the productivity and its success.
Planting
SRC can be planted on a wide range of soil types from heavy clay to sand, including land reclaimed from gravel extraction and colliery spoil. Where used as a pioneer speciesPioneer species
Pioneer species are species which colonize previously uncolonized land, usually leading to ecological succession. They are the first organisms to start the chain of events leading to a livable biosphere or ecosystem...
the SRC yield may be smaller. Water availability to the roots is a key determinant for the success of the SRC.
Saplings are planted at a high density, around 15,000 per hectare
Hectare
The hectare is a metric unit of area defined as 10,000 square metres , and primarily used in the measurement of land. In 1795, when the metric system was introduced, the are was defined as being 100 square metres and the hectare was thus 100 ares or 1/100 km2...
for willow and 12,000 per hectare for poplar. Planting takes place around March to take advantage of the high moisture of the soil in the spring and the amount of sunshine in the early summer. The most efficient planting machines plant four rows at a time and can plant a hectare in around three hours. Saplings are left to grow for a year and then coppiced.
The primary barrier to establishing plantations is the cost as there is no financial reward for four years from a large initial investment. However, in the UK grants are available to support establishment
Harvesting
Harvests take place on a two to five year cycle, and are carried out in winter after leaf fall when the soil is frozen. The established root system and the nutrients stored in the roots and stumps guarantee vigorous growth for the shoots. A plantation will yield from 8 to 18 tonnes of dry woodchip per hectare per year. A plantation can be harvested for up to thirty years before needing to be replanted.When willow or poplar shoots are harvested as whole stems they are easy to store. The stems can be dried for combustion in a pile outdoors; the moisture content of the wood will decrease to about 30% on average until the next autumn. The stems can be cut further into billets that may not need to be chipped depending on use.
Where wood chip is being produced it is most efficient to use direct-chip harvesters. These are heavy self-powered machines that cut and chip the shoots on a loading platform. Some can be attached to a normal tractor and a hectare can be harvested in around 3 hours. Direct chipping reduces costs as a separate chipping in the store will not be needed; however, the wood chip needs to be well stored to avoid it composting. Harvesting Poplar requires heavier machinery as it produces fewer and heavier stems.
The price of dry willow as a heating fuel is currently around 45 euro per tonne in most of Europe. This is not a relatively high-return crop, but it is low-maintenance and is a way of utilising difficult fields. Small scale production can be combined with the production of material for wicker
Wicker
Wicker is hard woven fiber formed into a rigid material, usually used for baskets or furniture. Wicker is often made of material of plant origin, but plastic fibers are also used....
work. Correctly managed there is little need for pesticides or treatments.
Greenhouse gases
SRC has a low greenhouse gasGreenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...
impact as any carbon dioxide released in power generation will have been sequestered by the plantation over just a few years. Some carbon may also be stored in the soil, however the extent of this carbon storage is dependent on the carbon content of the soil to begin with.
The carbon costs associated with SRC are: the planting, farming and chipping of the SRC plantation, generally done with fossil fuel
Fossil fuel
Fossil fuels are fuels formed by natural processes such as anaerobic decomposition of buried dead organisms. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years...
powered machinery; the crops require herbicides during establishment, fertiliser throughout growth, and occasional pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...
treatment - these chemicals require substantial amounts of energy and potential fossil fuel usage through manufacture.
Electricity or heat from SRC provides between three and six times the CO2 reduction per pound that can be obtained from bioethanol from cereal crops. However, the reduction in CO2 emissions is slightly lower than grass energy crops such as Miscanthus
Miscanthus
Miscanthus is a genus of about 15 species of perennial grasses native to subtropical and tropical regions of Africa and southern Asia, with one species Miscanthus is a genus of about 15 species of perennial grasses native to subtropical and tropical regions of Africa and southern Asia, with one...
grass due to higher maintenance costs.
Biodiversity
Good conservation management encouraging biodiversity can reduce the reliance on pesticides. Biomass crops such as SRC willow show higher levels of biodiversity in comparison with intensive arable and grassland crops.SRC has a higher water consumption than agricultural crops. The root systems of SRC have a lower impact on archaeological remains than forestry but greater than agricultural crops such as wheat.
Energy generation
A power station requires around 100 hectares (1 km²) of SRC for 1 MW of power capacity. The current nature of the power industry generally requires flexibility in energy supply which is incompatible with the long term commitment SRC requires; however, there is much interest in SRC due to the need to reduce fossil carbon emissions. Grants may also be available in some jurisdictions to further this type of land-use.See also
- BiomassBiomassBiomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
- BioenergyBioenergyBioenergy is renewable energy made available from materials derived from biological sources. Biomass is any organic material which has stored sunlight in the form of chemical energy. As a fuel it may include wood, wood waste, straw, manure, sugarcane, and many other byproducts from a variety of...
- Energy forestryEnergy forestryEnergy forestry is a form of forestry in which a fast-growing species of tree or woody shrub is grown specifically to provide biomass or biofuel for heating or power generation....
- MiscanthusMiscanthusMiscanthus is a genus of about 15 species of perennial grasses native to subtropical and tropical regions of Africa and southern Asia, with one species Miscanthus is a genus of about 15 species of perennial grasses native to subtropical and tropical regions of Africa and southern Asia, with one...
- Non food cropsNon Food CropsThe term non food crop applies to the use of agricultural crop for uses other than human or animal consumption .The range of crops with non-food uses is broad...
- PoplarPoplarPopulus is a genus of 25–35 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar , aspen, and cottonwood....
- Short rotation forestryShort rotation forestryShort Rotation Forestry is grown as an energy crop for use in power stations, alone or in combination with other fuels such as coal. It is similar to historic fuelwood coppice systems.- Species used :...
- SwitchgrassSwitchgrassPanicum virgatum, commonly known as switchgrass, is a perennial warm season bunchgrass native to North America, where it occurs naturally from 55°N latitude in Canada southwards into the United States and Mexico...
- WillowWillowWillows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere...
- Wood fuelWood fuelWood fuel is wood used as fuel. The burning of wood is currently the largest use of energy derived from a solid fuel biomass. Wood fuel can be used for cooking and heating, and occasionally for fueling steam engines and steam turbines that generate electricity. Wood fuel may be available as...