A guide to clean and proper heating EDITION 2013 Umschlag_engl final 14.5.2013.indd 3 14.05.2013 11:42:15 Umschlag_engl final 14.5.2013.indd 4 14.05.2013 11:42:23 WOOD HEAting and clean air – Aren’t theSE TWO CONFLICTING CONCEPTS? When correctly used, wood is an eco-friendly fuel. By using well-processed wood from local sources in a properly handled modern fireplace, you can enjoy the cosy warmth from your wood-burning stove or boiler without causing significant environmental damage. The environment and your neighbours will be grateful for this. This brochure is intended to give you tips on how to properly operate a wood-based heating system – in technical terms referred to as a small combus- tion installation. Especially the burning of poor quality wood in old and insufficiently maintained stoves and unfavourable combustion conditions will result in the emission of unnecessarily high levels of greenhouse gases having adverse effects on the climate, and pollutants detrimental to your health. Particularly in urban agglomerations and valleys, the air quality is affected by wood heating systems due to low chimneys. Often, neighbours will feel annoyed. 1 Layout_engl final 14.5.2013.indd 1 14.05.2013 11:32:17 WHAT HAPPENS WHEN WOOD BURNS? Burning or combustion designates a rapid oxidation of matter associated with flame formation. When wood burns, oxygen in the air combines with carbon and hydrogen con- tained in the wood. During this process, energy is released in the form of heat and light. Ideally, the only products of complete combustion are carbon dioxide, ashes formed primarily by the mineral components of the wood, and water. Roughly, the combustion process of solid fuels can be divided into three phases: Heating and drying – In this first phase, the water and other volatile substances pre- sent in the fuel will evaporate. Pyrolysis – In this second phase, the fuel will decompose at temperatures of about 150 degrees Celsius (°C) and above. During this process, a gas mixture is formed, which contains carbon monoxide, hydrocarbons and other compounds. In addition, oils and tars are formed, which undergo further decomposition at higher temperatures. At temperatures of about 400 to 500°C and above, also the solid organic components will gasify, combine with atmospheric oxygen and form predominantly carbon monoxide. At this stage, only charcoal will remain from the wood that served as a starting material. Combustion proper – In this third phase, the gases formed in the first two phases will react with additional atmospheric oxygen to form carbon dioxide and water. Also any remaining charcoal will burn down completely with time, in the firebed of the combus- tion zone. Only ashes remain as the single residue from combustion. Each phase of combustion can be observed very easily in an open fire. 2 Layout_engl final 14.5.2013.indd 2 14.05.2013 11:32:21 Emissions cannot be completely the carcinogenic polycyclic aromatic avoided hydrocarbons (PAH) in the ashes and Ideally, combustion of wood will produce the flue gas, and unpleasantly smelling only carbon dioxide, ashes and water compounds. Using materials for hea- (see box). The carbon dioxide produced ting that must not be burned such as will not contribute to global warming wood treated with wood preservatives if the amount of wood burned does not or paints, may even result in the for- exceed that of regrowing wood, be- mation of dioxins and furans (highly cause regrowing trees and shrubs will toxic substances that had been involved bind the carbon dioxide formed during in the Seveso chemical accident in the combustion. However, the wood used 1970s). should originate from your local sour- ces because any transport of wood to T here are four essentials to achieve clean your place of residence would involve heating the consumption of petrol or diesel. Operating your wood-fired heating In practice, wood will always contain system in such a way as to avoid un- certain low amounts of nitrogen com- necessary effects on the climate and pounds, sulphur compounds and chlo- human health is fairly simple. It should rine compounds. This is why harmful be based on four essentials: nitrogen oxides and sulphur oxides as Þ A low-emission and efficient fireplace; well as hydrochloric acid are formed during combustion. In addition, dust is Þ Suitable, dry fuel material that has released into the air, 90 % of which con- been properly stored; sists of fine particulates. These ultrafine Þ Proper operation of the system; and particles are not visible for the unaided human eye. They may enter the lungs Þ Regular maintenance and inspection of by inhalation and therefore, are hazar- the installation by trained professionals. dous to health. Adverse health effects may include bronchitis, an increase in asthmatic attacks and stress on your cardiovascular system. In addition, fine particulates are suspected of being carcinogenic. Incomplete combustion may also result in the formation of carbon monoxide, a toxic gas, and methane, a climate- damaging gas. Methane has a global warming potential 21 times as strong as that of an equivalent amount of carbon dioxide. Other products formed during incomplete combustion include organic compounds, among others also 3 Layout_engl final 14.5.2013.indd 3 14.05.2013 11:32:24 T HE SUITABLE TYPE OF INSTALLATION WHICH TYPES OF WOOD-FIRED INSTALLATIONS EXIST? 4 Layout_engl final 14.5.2013.indd 4 14.05.2013 11:32:28 If you consider using wood for heating, you will have to choose from different types of installation: R oom heaters Mostly used as a comfort and sup- plemental heating, a room heater is intended to heat a single room or two adjacent rooms. Heat is delivered by stoves predominantly in the form of appliances (slow combustion) or inter- radiant heat. Some types of stoves are mittent burning appliances. They differ equipped with additional air/water heat in the period needed for combustion THE SUITABLE TYPE OF exchangers and capable of supporting a until reloading of fuel is required. central heating system. Intermittent burning appliances are INSTALLATION predominantly used only during the Open fireplaces and fireplaces with transitional seasons because their use WHICH TYPES OF heating insert for permanent heating involves consi- WOOD-FIRED In open fireplaces the combustion zone derable effort. Modern wood-burning is open to the living room. This is why stoves often have a large door with a INSTALLATIONS EXIST? they are unable to control the supply of window pane. combustion air. Due to low combustion Tiled stoves (storage heaters) temperatures and too much excess air, open fireplaces usually produce high More than 50 % of the outer casing of levels of pollutants while delivering tiled stoves is made of stove tiles, tile only little heat. A better option is provi- stones or plastered surfaces. Additional ded by fireplaces with a heating insert functions may be included such as the because they are closed by means of preparation of hot water for consump- a glass door or glass pane. Thus, con- tion or heating. trolling air supply becomes easier, and Masonry or storage heaters have a large energy efficiency is improved. mass capable of heat storage consisting Free-standing room heaters with or of tiles, cement plaster, clay, chamotte without a window pane or soapstone. The large surface of these stoves reaches relatively low tempera- In free-standing room heaters logs are tures (80 to 130 degrees Celsius) only. placed directly into the combustion Storage heaters are operated under chamber through a door. The ashes in full load during the combustion phase the ash pan can be removed through (about one hour), and the stored heat an opening in the lower part of the continues to give off warmth to the stove. The air quantity supplied can air in the room for many hours. In the be controlled by means of opening majority of cases, operating the heater or closing dampers and valves or the at reduced combustion, i.e. with redu- ash removal door. These room heaters ced air supply in order to maintain a are available as continuous burning firebed for as long as possible, is not 5 Layout_engl final 14.5.2013.indd 5 14.05.2013 11:32:28 required. This is why these systems bustion chamber. The supply of fuel produce relatively low emission levels. is automatically adjusted depending Overheating of rooms will hardly ever on the thermal output required. Pellet occur with storage heaters. heaters are available as free-standing wood-burning stoves with a window Warm-air tiled stoves consist of a pane or tiled stove heating inserts. Pel- heating or fireplace insert and most lets produce lower emission levels than often, a metallic heating gas flue. They other wooden fuels. In addition, their are cased with stove tiles, tile stones or use is much more convenient than that other mineral building materials. The of split logs because pellet heaters work warm-air tiled stove heats the room by largely automatically. The pellets can passing the warm air through air ducts. be stored and dispensed in an optimal Heat is emitted mainly by convection. way. As compared to storage heaters proper, warm-air tiled stoves have a lower heat storage mass, heat emission after star- C entral heating boilers ting the fire takes less time. Central heating boilers heat both the entire home and the water for human Þ Pellet stoves consumption. Like oil and gas boilers Pellets are made from compressed also wood-burning boilers are mostly natural wood shavings and sawdust. placed in a special boiler room. There is a special feature to pellet Þ Manually fed log wood boilers stoves: The fuel is fed automatically and continuously from a storage hopper (20 In wood-burning central heating boi- to 30 litres) to a burn pot in the com- lers, the technology predominantly used is that of the downdraught type.