Properties and applications of pellets
The interest in issues related to environmental protection and reducing emissions of harmful substances into the atmosphere, while wanting to keep heating costs as low as possible, makes the use of wood pellets for heating purposes increasingly interesting. Let us find out what pellet is and what its useful properties are. Wood pellets are one of the solid fuels that can be successfully used in central heating boilers. Wood pellets are produced from wood that has been heavily chipped and is formed into small cylindrical granules under very high pressure. They are relatively cohesive and hard, thanks to which the raw material retains its shape during transport, storage and when adding to the boiler.
Wood pellets are produced from specially grown wood on plantations. Often, special energy crops such as poplar or willow are also used to produce it. Pellets can also be made from parts of felled trees that cannot be used in other ways – branches, trimmings, and sometimes bark. Relatively often, chips and waste from wood processing plants are also used as raw material.
Advantages of heating with wood pellets
A great advantage of pellets is their high calorific value and relatively low ash content. Thanks to that during combustion a small amount of ash is produced. Burning with pellets also means very low emissions of particulate matter, volatile organic compounds or carbon dioxide. A characteristic feature of pellets is zero carbon dioxide balance, which means that burning this raw material releases at most as much CO2 as the plants from which it is produced have absorbed during their growth. The combustion of pellets also produces only a small amount of nitrogen oxides.
The use of pellets is also very convenient. The material can be packed in bags to ensure protection from moisture and external conditions. Pellets are ideal for central heating boilers with automatic feeders, into which it is easy to pour from small and handy bags.
Due to the raw material from which it is produced, pellets are classified as biomass, and therefore as a renewable energy source. Therefore, heating buildings with pellets combines ecology with low fuel costs and comfort of use.
Are pellets an environmentally friendly fuel?
Pellets are a renewable energy source derived from wood chips and sawdust, the residues from the processing of wood. It is produced from wood waste, crops grown for this purpose, and agricultural waste and by-products. The wood used to make pellets can be either hardwood or softwood – there are also more exotic blends coming from palm wood, coconut shells or even logs and branches. It is one of the most environmentally friendly fuel materials.
When and why did pellets become so popular?
Pellets appeared on the market in 1993.
The demand for this type of biomass increased after 2005 (especially in Europe and North America) due to a sharp increase in coal and gas prices.
A very important aspect was also the fact that some Western European countries introduced a ban on burning coal, which, among other things, made wood pellets the cheapest source of heat, comparing favourably with briquettes, eco-peas, fuel oil, gas and electricity.
Why is pellet such an environmentally friendly material?
Here are some basic facts about one of the most environmentally friendly fuel materials. Here is what characterizes pellets:
- It emits very little particulate matter, volatile organic compounds and carbon dioxide (in the case of CO2, emissions are equal to the amount absorbed by the plant during growth, so the balance is zero unless you add the production of CO2 during production and transport)
- The resulting small amount of ash (5 kg per tonne of biomass burned) can later be successfully used as a natural, ecological fertilizer
- This fuel is very efficient due to its high resin content
Ecology and convenience go hand in hand!
Pellets are convenient to store (also on site, at the customer’s) – the material can be packed in bags to protect it from moisture and external conditions. Pellets are perfect for central heating boilers with automatic feeders, where it is easy to pour them into small and handy bags.
Heating buildings with pellets combines ecology with low costs and comfort of use.
What affects the calorific value of pellets?
How is pellets made?
Pellets are made from waste raw materials, which are the result of the activities of sawmills, woodworks or carpenter’s workshops. The material obtained in this way needs to be crushed further, which makes it possible to dry the raw material later.
It is worth mentioning that it must be a cleaned material, i.e. one that does not contain any chemicals or minerals. To clean the pellets, special machines are used, which remove the remaining soil, metal fragments or stones. Only after it has been thoroughly cleaned, it can be segregated, thanks to which only high quality wood mass goes to further stages of production.
It is assumed that the pellet material should have a moisture content of no more than 8%, so that it burns more efficiently. To dry the raw material to this level, dehydration is used, during which the material is heated so that the water in it begins to evaporate.
The most important stage, however, is granulation, since the quality of the pellets depends on it. The granulation process also takes place using a special machine which presses out the wood pulp. The specification of the granualtor must be adjusted to the specific type of wood, as otherwise the whole material may be destroyed.
What is done with the pellets already made?
After the manufacturing process is completed, it has to be cooled, then sieved and at the very end it is packed into bags. Thus prepared and packed pellets can be purchased in stores.
As you can see, the process of making pellets is complex and requires the use of several different machines if we want the final product to be of high quality. The price of pellets can certainly be described as adequate to the quality, or even lower than expected.