Ash Content and Quality of Premium Grade Wood Pellets

Compared to industrial wood pellets, which have looser specifications, particularly regarding ash content, which can reach 6%, premium-grade wood pellets, for use in space heating, have stricter specifications, specifically a maximum ash content of 1%. Premium-grade wood pellets generally have a diameter of 6 mm, while industrial pellets are generally 8 mm. The color or appearance of premium-grade wood pellets also plays a role, with brighter colors generally preferred. This is why premium-grade wood pellets are naturally more expensive. Demand for premium-grade wood pellets increases during the winter due to the increased need for space heating.

Regarding ash content, several standards even stipulate ash content lower than 1%, such as DIN Plus with a maximum of 0.5%, ENPlus-A1 with a maximum of 0.7%, and Ö NORM M7135 which requires a maximum of 0.5%. This is why strict control of raw material selection and treatment is applied in the production of wood pellets to meet these specifications. Although the ash chemistry for premium grade wood pellets may not be as stringent as for industrial pellets because the application operation is at lower temperatures, the production of wood pellets with very low ash content requires high-quality raw materials.

In premium grade wood pellets, even a slight difference in ash content can significantly impact the selling price. For example, wood pellets with a maximum ash content of 0.55% can differ by around USD 30 per ton compared to wood pellets with a maximum ash content of 0.35%. Because they are used for space heating, premium grade wood pellets are generally packaged in small plastic bags, such as 15 kg, while ordinary industrial pellets are packaged in jumbo bags or even bulk due to the much larger volume requirements.
 

Premium Wood Pellet Production From Plywood Factory Waste

Indonesia's plywood or plywood production is estimated to be more than 10 million cubic meters annually, which is produced from hundreds of plywood factories, even Indonesia once dominated the world's wood industry in the period from 1980 to 1995. There are five provinces as the largest plywood producers in Indonesia, namely East Java, East Kalimantan, Central Java, South Kalimantan and West Kalimantan. And six other provinces that are starting to develop, namely Banten, Papua, Central Kalimantan, South Sulawesi, Riau and Jambi. Most of the plywood is for the export market.

The volume of wood waste in the plywood industry is quite large, reaching almost 55% or more than 5 million tons per year of the national plywood production. The potential for this waste is quite large and has great potential to be processed into premium grade wood pellets. Why is wood pellet an option and why does it have to be premium grade? Wood pellets are the choice for the solution to the plywood waste problem because in addition to an easier production process, machine investment is also cheaper. This is because the wood waste from the plywood factory is dry, so it does not require a drying process. The dryer is not only quite expensive but also the operational costs. Premium quality is also possible due to the low ash content, because the wood for the plywood production has been debarking so that the ash content can be reduced to below 1%.

Size reduction / down sizing is the first thing that needs to be done with the plywood waste. After the particle size is appropriate, which is the size of sawdust (~3-5 mm), then the wetting process is carried out until the moisture content reaches about 10%. This is because the wood waste from the plywood factory is usually too dry, with a moisture content of 4-5% so that it does not meet the requirements for pelleting. Raw materials that are too dry make pellet gluing not optimal, so that pellets become brittle and even pellets are not formed at all. The wetting process is carried out with a water sprayer to reach the moisture content level. After the water content reaches about 10%, then the raw materials enter the pelletiser to be pressed or molded into pellets.

The premium grade wood pellet market segment is different from standard or utility grade wood pellets according to the table above. The use of premium grade wood pellets is for heating, especially in winter in countries with four seasons. The main reason for using premium grade wood pellets for this purpose is the very low ash content. With a low ash content, ash cleaning becomes less frequent. In general the production of premium grade wood pellets is more difficult than standard or utility grades, but especially in the plywood industry with the conditions of the raw materials as above, it is much easier and more prepared for the production of premium grade wood pellets. A golden opportunity for those who realize and understand it.

Energy Production from Pellet Fuel

The pellets fuel are a modern form of densified biomass offering interesting opportunities for development of Renewable Energy in Indonesia, consisting of wood pellets and biomass pellets. Wood pellets derived from wood and biomass pellets derived from biomass such as agricultural wastes and plantations such as oil palm empty fruit bunches. Pellet fuel that be produced could have a large variation in quality because of the raw materials and production technologies. Technology for pellet fuel utilization in thermal route for energy production which is burning and gasification has been applied.

The production of energy from pellets fuel in the form of heat and electricity. Heating with pellets fuel is normally quite simple and the need for inspection and care of the burner and boiler is often limited. However, combustion problems can arise e.g. if the amount of ash increases causing the system to slag and the efficiency to decrease. These problems are often caused by the low quality of pellets fuel or by wrong choice of the plant or system settings.

Calorific value, ash content, ash chemistry, moisture content, dimension and density pellets are several important parameters of pellet fuel. Preference type of pellet fuel will determine the combustion technology. Currently available equipments to burn pellets fuel from the household scale (pellet stove), medium scale up to production of heat and electricity for large scale up to tens of megawatts (MW). Equipment or systems are generally equipped with air regulation valves either primary or secondary and even tertiary to optimize the combustion process is done. Setting the correct operation make the system work optimally match to the specification.