Pellets, or wood pellets, have become an essential source of renewable energy for heating in an ecological and economical way. However, not all pellets are equal in terms of performance and durability. So, how do you recognize a good pellet? Here are some criteria to take into account to help you make the right choice.
Certification: guarantee of quality
To ensure that your pellet is of good quality, it is essential to check that it has a recognized certification. The best-known certifications are the European ENplus standard and the French NF standard. These labels guarantee that the pellets comply with strict requirements in terms of composition, calorific value, humidity level and ash.
The ENplus standard
The ENplus standard classifies pellets into three categories:
- ENplus A1: these are high-end pellets, intended for individuals. Their humidity level is less than 10%, their calorific value is greater than 4.6 kWh/kg and their ash content is less than 0.7%.
- ENplus A2: these pellets have slightly lower characteristics than A1, but remain of good quality.
- ENplus B: these pellets are intended for industrial use and are not suitable for individuals.
The NF standard
The NF standard also guarantees the quality of pellets, based on criteria similar to those of the ENplus standard:
- Calorific value greater than 4.6 kWh/kg
- Humidity level less than 10%
- Ash content less than 0.7% for Premium pellets and 1.5% for Standard pellets
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Pellet hardness: a key performance factor
A good pellet should be sufficiently hard and durable to avoid decomposition during transportation, storage and use. Too much fragility leads to the production of dust and fine particles, which can clog the heating system and harm its efficiency.
The hardness of pellets is generally expressed by their mechanical durability index (MDI), which must be greater than 97.5%. The higher this index, the more solid the granules are and resist handling.
The origin and composition of pellets
To obtain a quality pellet, it is important to ensure that it is made from clean, untreated wood. Pellets made from by-products of the wood industry (sawdust, shavings) are generally of better quality than those made from recycled wood or plant waste. Geographic origin can also be a factor to consider, because it influences the characteristics of the wood used, and therefore the quality of the pellet.
Additionally, check the type of binder used to bind the wood particles together. The best pellets are obtained by using lignin naturally present in wood, without the addition of chemical additives.
The size of the pellets
The size of the pellets plays an essential role in their energy performance. The ENplus standard recommends length between 3.15 and 40 mm and one diameter of 6 or 8 mm. These dimensions allow optimal combustion and regular supply of the heating system.
It is also important that the particle size (distribution of pellet sizes) is homogeneous, in order to avoid variations in performance and malfunctions of the pellet stove or boiler.
Humidity rate and calorific value
A good pellet must have a low humidity level (<10%) and a high calorific value (>4.6 kWh/kg), which guarantees efficient combustion and maximum efficiency. Too high a humidity level leads to a reduction in calorific value, as well as increased production of condensates and ash.
The calorific value of pellets depends in part on their composition: pellets made from softwood (pine, fir) generally offer better performance than those made from hardwood (oak, beech).
Ash content
Finally, the quality of a pellet is also measured by its ash content, which must be as low as possible (<0.7% for Premium pellets, <1.5% for Standard pellets). A low ash content helps reduce polluting emissions and clogging of your heating system, while making it easier to maintain.
In summary, to recognize a good pellet, it is necessary to check its certification, its hardness, its composition, its dimensions, its humidity level, its calorific value and its ash content. Do not hesitate to compare the technical characteristics of the different products available on the market and to favor brands that have proven themselves in terms of quality and performance.