Short rotation coppice

Short rotation coppice

Short Rotation Coppice (SRC) is grown as an energy crop. This woody solid biomass can be used in applications such as heating, electric power generating stations, alone or in combination with other fuels.

Species used

SRC uses high yield 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 beetles, as well as the fungal pathogen "Melampsora" (a rust), planting a carefully selected mix of varieties is recommended.

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 species 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 first three years are part of the establishment phase and do not yield much dry matter.

Harvesting

After four years the plantation will be ready for harvest. Harvests take place on a two to five year cycle, shorter for willow and longer for poplar, 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 work. Correctly managed there is little need for pesticides or treatments.

Greenhouse gas impact

SRC has a low greenhouse gas 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 this 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.

Environmental impacts

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 primary barrier to establishing plantations is the cost as there is no financial reward for four years from a large initial investment. 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

* Energy forestry
* Miscanthus
* Non food crops
* Short rotation forestry
* Switchgrass
* Wood fuel

References

* [http://www.defra.gov.uk/erdp/pdfs/ecs/src-guide.pdf Growing short rotation coppice (PDF)]
* [http://www.forestry.gov.uk/srcsite/INFD-5JPHSM Establishing an SRC plantation]
* [http://www.forestry.gov.uk/src Yield Models for Energy Coppice of Poplar and Willow]
* [http://www.dti.gov.uk/files/file34448.pdf Evaluating the Sustainability of Co-firing in the UK (PDF)]
*Greenergy - [http://www.greenergy.com/SRC/overview.html Short Rotation Coppice]
* [http://www.publications.parliament.uk/pa/cm200506/cmselect/cmenvfru/965/96507.htm Select Committee on Environment, Food and Rural Affairs]


Wikimedia Foundation. 2010.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • Short rotation forestry — (SRF) 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 SRF is the practice of cultivating fast growing trees that reach… …   Wikipedia

  • Coppicing — Coppice redirects here. For the locality in Oldham, see Coppice, Greater Manchester. For Bahamian coppice forests, see Bahamian dry forests. A recently coppiced alder stool in Hampshire …   Wikipedia

  • Energy forestry — is a form of forestry in which a fast growing species of tree or woody shrub is grown specifically to provide biofuel for heating or power generation. The two forms of energy forestry are short rotation coppice and short rotation forestry. Short… …   Wikipedia

  • England Rural Development Programme — is the instrument by which the UK Department for Environment, Food and Rural Affairs (Defra) fulfills its rural development obligations in England, as set out by the European Union. It is derived primarily from Council Regulation European Union… …   Wikipedia

  • Woodchips — are a solid fuel made from woody biomass. They are made in the process of woodchipping with a woodchipper. They are used primarily as a heating fuel in a few commercial institutions, such as schools, and in some industrial plants for generating… …   Wikipedia

  • Erneuerbare Energie in Schottland — Wind, Wellen und Tidenhub machen mehr als 80 % von Schottlands erneuerbarem Energiepotential aus. Die Produktion von erneuerbarer Energie in Schottland ist ein Gebiet, das in den ersten Jahren des 21. Jahrhunderts in den Blickpunkt der… …   Deutsch Wikipedia

  • Willow — Salix redirects here. For other uses, see Salix (disambiguation). Osier redirects here. For the ghost town, see Osier, Colorado. For other uses, see Willow (disambiguation). Willow Salix alba Vitellina Tristis …   Wikipedia

  • Outline of forestry — See also: Index of forestry articles The following outline is provided as an overview of and guide to forestry: Forestry – the art and science of managing forests, tree plantations, and related natural resources. Forest ecosystems have come to be …   Wikipedia

  • 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 (grassy).… …   Wikipedia

  • Renewable energy in Scotland — The production of renewable energy in Scotland is an issue that has come to the fore in technical, economic, and political terms during the opening years of the 21st century. [See for example: Scottish Executive (2005) Choosing Our Future:… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”