A method for compacting biomass is pelletizing with a pelletizer. Biomass pellets are used in the feed industry, but also as a solid fuel for boilers.
Pelletizing biomass is not always easy. Standard solutions do not always exist. In order to make a good pellet, a lot of research is sometimes necessary.
The dry matter content in biomass can differ a lot, is often low and the material might already be partly decomposed, lowering the quality and potential value of the product. In addition, the cost price for biomass is dependent on a lot of factors, such as the way it is harvested, processed, how it is transported and how far it had to be transported (often with a lot of air and moisture in the product, increasing the cost price even more). Still, the use of biomass pellets can be very profitable.
Fuel pellets are usually made out of wood (mainly sawdust, wood chips and shavings). In the Netherlands, many companies look to pellet fuels in order to replace expensive natural gas. Wood pellets are commonly used, but in the past, farmers experimented with burning grass and straw pellets in boilers too. Good research is of importance though. Agro-residues can contain higher levels of sulphur, chlorine and other substances which may cause technical problems in the boiler. Also, unknown emissions during combustion are important factors that are still part of research in the development of the biomass pellet market.
Utilities also look beyond wood pellets. In Denmark, Dong Energy is using pellets made out of lignin (one of the products from a 2nd generation ethanol plant). Lignin pellets are a good coal replacement. In comparison with straw, their big advantage is reduced alkali metals content. So high temperature corrosion has not been an issue in their experience when burned in boilers, suggesting great potential for lignin pellets to replace coal extensively in power stations.
There are also other important reasons for the pelletization of biomass. Pelletizing limits the creation of dust, ensures a better distribution, reduces transport costs (less air and moisture) and can be a way to add products into a composite product together.
Besides wood, other types of biomass (or even chemicals) can be pelletized. In general, other types of biomass contain more hemicellulose and cellulose and less lignin compared to wood. Therefore, it has less tensile and compressive strength. Our experts have pelletized different types of biomass. In order to avoid problems and create a pellet of high quality, we test how biomass is pre-treated and milled. The pellet should show a particular shine on the sides. Such a pellet will be consistent and will not produce a lot of dust when used or transported.
Normally, there is a sufficient amount of lignin in wood to bind the pellets. Other types of biomass might require different methods, such as the use of binders (such as starch, sugars or paraffin oils). Ask our experts about the possibilities.