Burn, economically and ecologically!
The biomass produced every year on our planet is estimated to amount to 172 billion tons of dry material, while in Greece, the annually available agricultural and forest residues are equivalent in energy to 3-4 million tons of oil, while the potential of energy crops can , with today's data, to comfortably exceed that of agricultural and forest residues. This amount corresponds in terms of energy to 30-40% of the amount of oil consumed annually in our country. However, with today's data, only about 3% of its energy needs are covered using the available biomass.
From a recent census, it has been estimated that the total biomass immediately available in Greece consists of approximately 7,500,000 tons of agricultural crop residues (cereals, maize, cotton, tobacco, sunflower, cladodes, vines, heartwood, etc.), as well as 2,700,000 tons of forest logging residues (branches, bark, etc.). In addition to the fact that the largest percentage of this biomass unfortunately remains unutilized, it is often the cause of many unpleasant situations (fires, difficulty in carrying out work, spread of diseases, etc.). Inevitably, therefore, one can conclude that the utilization of biomass in the field of home heating is a respectable proposition.
How we evaluate the quality of combustion
Like all combustion technologies, biomass home heating systems are evaluated based on the following key characteristics:
– The degree of efficiency (%), which is defined as the ratio of the useful heat produced by the combustion system to the energy provided by the burning fuel (expressed in terms of the lower calorific value).
– Combustion emissions, which mainly concern various gaseous pollutants such as carbon monoxide (CO), nitrogen oxides (NOx) and sulfur (SOx), unburned organic compounds and particles. The main goal of any combustion system is to maximize efficiency while minimizing emissions. This can be achieved by proper system design, correct fuel selection and appropriate adjustments during its operation, e.g. in the combustion air supply.
The fuel
Based on the definition, biomass is essentially any matter that directly or indirectly has a biological (organic) origin. If biomass is used as a fuel for energy production, we are talking about solid, liquid and gaseous biofuels, depending on their physical form. Solid biofuels include a wide range of materials, such as pellets, firewood, heartwood, etc. and are used to generate heat in the domestic sector. There is a huge number of materials with very different properties that can be classified as solid biofuels. In practice, the forms of solid biofuels commercially available are specific and mainly include the following:
– Pellets are small cylindrical particles, with a typical diameter of 6 – 8 mm. They are produced by a biomass compression process. In general, the production process of the pellets ensures the uniformity of the fuel and low moisture percentages (< 10% by weight). Today, the vast majority of pellets on the market are made of wood and are characterized by low ash content. It is also possible to make pellets from other materials (e.g. straw), but their production and use in the domestic sector is very limited due to the high ash content. In the Greek market, wood pellets are usually sold in 15 kg packages.
– The heartwood is the woody residue that results, due to the removal of moisture and the remaining oil (heart oil), from the semi-solid paste that remained after the production of olive oil in the olive mill. Heartwood is generally characterized by higher percentages of ash compared to commercial solid wood biofuels, while, according to Greek legislation, the oil content on dry matter must not exceed 2%.
– Briquettes are products of compression of biomass materials, usually cylindrical or rectangular in cross-section and much larger than pellets. They are usually made of woody materials and are characterized by low moisture and ash percentages.
– Wood chips are small pieces of wood, 5-50 mm long. The quality of biomass chips depends on the raw material and their production technology and they usually come from forest residues (branches, tops, whole trees), residues from sawmills, etc. They have not undergone compression or any non-natural drying process, so ' this usually has quite high humidity rates, which can reach up to 50%.
Combustion media
Home heating systems are characterized as:
– Central heating, in which the energy of the fuel is released through combustion in a boiler and is attributed to a carrier, which, through the distribution system, gives this heat to radiators suitably placed for heating different spaces.
– Local heating, when the energy is produced and supplied in the same space, without the intervention of a transmission system. Local heating systems include fireplaces (simple and energy air heaters) and stoves (simple and air heaters).
Don't forget to:
– urge the craftsman to also measure the draft after installing the chimney
– clean the chimney properly, since insufficient cleaning can cause a serious fire
- find out about the moisture content of the wood before buying
– remove the remains from the previous combustion (ashes, coals) to facilitate air circulation
Advantages
+ Prevention of the greenhouse effect
+ Avoiding atmospheric pollution with sulfur dioxide (SO2)
+ Reduction of energy dependence, from fuel imports from third countries
+ Securing work and retaining rural populations in agricultural areas
+ Renewable energy source
+ Automatic fuel supply (on devices with this feature installed)
+ Low fuel costs compared to conventional fossil fuels
Tips
– You choose the place of installation according to the safe use of the device, the position of the chimney and the supply of combustion air.
– Observe the specified minimum distances or clearance (>1 meter) from all combustible materials around combustion devices (stoves, energy fireplaces).
– Be careful when placing the flue gas exhaust pipes (mufflers) so that they do not come into contact with wood or other flammable surfaces.
– Remove flammable materials within a radius of 40cm from the chimney. It is forbidden to pass cables through the walls or the ceiling at a distance of 60cm from where the device is installed.
– Make sure that each chimney is connected to only one combustion device
– Do not place the stove on a carpet or near furniture or curtains.
– Store the wood in a place protected from rain and well ventilated (south side).
– Do not turn on the ventilation system at the same time as using the combustion device in the same room.
– Do not extinguish fire with water, especially on cast iron appliances where extinguishing with water can crack or break the cast iron.
– Install a carbon monoxide detector in the area where the combustion appliance is located.
*Reposted from www.4green.gr
Sources: Guide to Solid Biofuels & Biomass Boilers for Domestic Heating Applications of the National Center for Research and Technological Development (EKETA), Center for Renewable Energy Sources (K.A.P.E.), Association of Hellenic Heating-Energy Companies (EN .E.EPI.TH.E.)
