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Report 2 of 4: Off Piste -
Austria
Introduction
Biomass refers to biologically derived material of any kind. It is still the main source of energy for more than half the world’s population for domestic energy needs. Biomass is available in varying quantities throughout the world - from densely forested areas in the temperate and tropical regions, to sparsely vegetated arid regions where collecting wood fuel for household needs is a time consuming and arduous task. More than two million people in the developing world use biomass for the majority of their household energy needs. It is used mainly for cooking, heating water and the household but it is also used for non-domestic applications.
Solid biomass is the use of trees, plants, crop residues, animal and human waste, household or industrial residues for direct combustion to provide heat. Often the solid biomass will undergo physical processing such as cutting, chipping, briquetting, etc. but will still retain its solid form. Crop and industrial biomass residues are widely used in many countries to provide centralised processing of heat for electricity production or other commercial end uses.
Combustion of biomass
Solid biomass needs to undergo combustion in order to be converted into useful heat energy. The combustion process can take place within a basic open fire used for cooking or heating, although more sophisticated technologies exist for extracting energy and converting it into heat or power for medium and large scale operations. Combustion efficiency varies depending on the fuel and moisture content etc. The design of the stove or combustion system also affects the overall thermal efficiency.
All biomass contains moisture and this moisture has to be driven off before combustion can take place. The heat for drying is supplied by radiation from flames and from the stored heat in the body of the stove or furnace. The dry biomass is then heated and when the temperature reaches between 200 and 350ºC, gases are released. These gases mix with oxygen and burn producing a yellow flame. The heat from the burning gases is used to dry the fresh fuel and release more gases. Once all the gases have been burnt off, charcoal remains. At about 800ºC, the charcoal oxidises or burns.
Biomass energy in Austria
Austria is one of the most densely wooded countries in Europe with about 45% of its area being covered by forests. Traditionally, biomass has been used for energy production. Currently, energy from biomass provides about 13% of Austrian primary energy consumption. About 60% of this energy is used to power traditional stoves and boilers, fired with wood-logs.
In order to encourage the industrial use of biomass, the Austrian Government has set up a major action programme to support companies switching their heating systems to biomass or supplying energy from biomass to third parties.
The sawmill, paper and wood pulp, and wood working industries, such as construction, furniture and ski manufacture, and craft workshops, are the main users of biomass energy, usually as a by-product of their own activities.
Utilisation of biomass
Approximately two thirds of the timber (without bark) which is processed in sawmills is converted to sawn timber. The remaining timber and the bark are used for further processing and for energy production. As most sawmills are equipped with bark peeling machines, wood residues tend to be bark-free which makes them suitable for further processing in the paper and wood pulp industry, where they fetch a higher price. Therefore, it is mostly the bark that is used for energy production.
Residues of the paper and wood pulp industry, such as bark and black liquor from pulp production, are mainly used to supply the industry’s own electricity and heat demand. Austria’s wood working industry also produces a considerable quantity of waste wood. About 70% is used as fuel for producing energy and about 30% is processed further, mainly in paper and board production.
Biomass District Heating Plants
In the last 15 years, a new technology for providing domestic heating in rural areas has been introduced: small scale district heating plants that use wood chips, industrial wood wastes and straw as fuel. Now more than 300 Biomass District Heating Plants (BMDH) have been established in rural villages in Austria.
A BMDH system operates using a big furnace fuelled with biomass to heat water that passes through a pipe grid and supplies the energy for the heating of individual houses in a village with between 500 and 4000 inhabitants. Accordingly, the size of BMDH plants varies from a few hundred kW, up to 8 MW, with corresponding grids between 100 metres and 20 km. About two-third of all the plants have a power of less than 1500 kW.
Biomass district heating has a number of significant advantages compared to traditional heating systems. It substitutes all fuel handling work, provides continuous heat and reduces emissions of predominantly old and technically poor individual heating systems significantly.
Biomass energy in Lech
The popular ski resort of Lech in Austria is situated in a valley. In winter, the pollution caused by the oil heating used in the hotels and other buildings in the village hangs over the valley. A biomass heating plant has just been built to improve the level of pollution and air quality.
The energy to fuel the biomass plant comes from a renewable energy source available in large quantities in Austria – residues from the paper and wood pulp industry. This type of fuel does not pollute the environment. It is produced from a natural organic material which is readily available from local sources, such as wood chips, or the bark from trees or the sawdust from industry.
The biomass is transported from the conveyor system directly to the biomass oven where it is heated up to 1100ºC and distributed as warm water in pipes throughout the village. The outgoing temperature is approximately 100ºC and the incoming temperature from the pipes is about 50ºC.
It is the first time in Europe that an entire tourist resort has been heated using biomass. The village was offered free connection to the new power plant by the federal and local government as an incentive to dispense with their oil fuelled heating systems. Currently, 90% of the hotels, households and buildings in the resort have taken up the offer. The biomass heating plant replaces the use of 3.5 billion litres of oil which reduces carbon dioxide emissions by about 10,000 tons each year. Furthermore, Austria is able to sustain this non-polluting method of heating because of its abundance of trees.
Domestic heating
More than 570,000 homes are currently heated by wood-fired systems, many of which are already equipped with modern combustion technology. Over 70% of biomass is used in low-temperature applications, i.e. the combustion of wood or wood chips in single heaters or central heating boilers in the case of small-scale users, or of various fuels such as bark, sawmill residue, wood chips, or straw in biomass-fired district heating systems.
For further information, please contact:
Austrian Energy Agency - E.V.A.
Linke Wienzeile 18
A-1060 Vienna
Austria
Tel: +43 1 586 15 24
Fax: +43 1 586 94 88
E-mail: eva@eva.wsr.ac.at
Website: http://www.eva.wsr.ac.at/ |
Federal Ministry of Science and Transport
Minoritenplatz 5
A-1014 Vienna
Austria
Tel: +43 1 531 20-0
Fax: +43 1 531 20-6480
Website: www.bmwf.gv.at/ |
Intermediate Technology Development Group would like to thank the Austrian Energy Agency and the Austrian Federal Ministry of Science and Transport for providing the original information on biomass as a source of renewable energy.
Further reading available from ITDG Development Bookshop
Power Plants: An Introduction to Biofuels
B. Horne
Centre For Alternative Technology £5.50 1996
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This document is an output from a project funded by the UK Department for International Development (DFID) for the benefit of developing countries. The views expressed are not necessarily those of the DFID.
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