Wood pellet standards
The biofuel such as wood pellets, which is so popular in European countries, is produced with the necessity to follow certain quality control norms. These norms are described in several standards, developed by different countries. In order to reveal the advantages and weaknesses of each, their main characteristics are described below:The first standard, DIN 51731, developed in Germany, is not completely perfect because it doesn’t contain some important parameters for wood pellets such as abrasion which is a criterion for hardness and stability of pellets. Moreover, according to the standard, an independent examination of the manufacturing process is not an obligatory.
The second standard, ONORM 7135, developed in Austria, as opposed to a previous one, contains more limitations and specifies the parameter of abrasion. Following the standard, abrasion is to be tested by exposing pellets to a certain pressure in a Lignotester. The degree of abrasion is of considerable importance because it influences the level of emissions occurring during the process of blowing them into the bunker.
The strictest standard is revealed to be a certification according to DIN plus, where the developers have combined the above mentioned norms. The enterprise, certified by this standard, is obliged to have regular inspections in order to provide constantly the highest quality of the product.
The following table allows to compare the requirements of all three standards for wood pellets quality:
Wood pellets quality norms |
ONORM M 7135 |
DIN 51731 |
DIN plus |
|
Diameter |
mm |
4 to 10 mm |
4 to 10 mm |
|
Length |
mm |
5xD1 |
< 50 |
5 x D a |
Density |
kg/dm3 |
> 1,12 |
1,0 < Density< 1,4 |
> 1,12 |
Moisture |
% |
< 10 |
< 12 |
< 10 |
Ash |
% |
< 0,50 |
< 1,50 |
< 0,50 |
Net calorific value (Qd) |
MJ/kg |
> 18 |
17,5 <Q< 19,5 |
> 18 |
Sulphur |
% |
< 0,04 |
< 0,08 |
< 0,04 |
Nitrogen |
% |
< 0,3 |
< 0,3 |
< 0,3 |
Chlorine |
% |
< 0,02 |
< 0,03 |
< 0,02 |
Abrasion |
% |
< 2,3 |
- |
< 2,3 |
Press aid |
% |
< 2 |
b |
< 2 |
