In recent decades wood pellets have become a conventional fuel for solid fuel fired power plants, industrial boilers and boilers for heating in housing and has become a commodity traded globally. Due to EU policy induced requirement for increased use of renewable energy a significant amount of pellets is utilized in the Netherlands too. The applied pellets - 1 Mtonne per year - are utilized as a fuel in coal fired power stations, substituting coal. Experiences at Avedore II power station illustrate that substitution of up to 80% of coal is technically feasible.
Wood pellets are produced by subsequently chipping, drying, and milling wood very finely. For provision of the heat utilized in drying, part of the wood is combusted. The finely milled wood is pressed through a mould at high pressure. The friction heat softens the wood. The soft wood is cut into pellets, which are screened for size, cooled and subsequently stored.
The pellets have a high hardness, which makes it possible to pulverize them to the particle size required by the burners in a coal fired power plant.
Pellet availability is likely to be limited. Dutch wood resources for pellet production are limited to approximately 2 Mtonnes per year. Imports are probably limited to approximately 10% of total Dutch energy consumption in 2050.
Wood pellets supplied to coal fired power stations are not completely climate neutral. Transport of pellets is associated with limited emissions of greenhouse gases. In commercial cultivation, use of fertilizers may give additional greenhouse gas emissions and high electricity use for pellet milling somewhat reduces the emission reduction. But on the whole substitution of coal by wood pellets would give a reduction in greenhouse gas emissions of over 90%.
This reduction percentage does not include greenhouse gas emissions related to so-called indirect land use change (ILUC). Indirect land use change resulting in degradation of forests or other natural landscapes with high amounts of vegetation would result in greenhouse gas emissions of such extent, that the direct reduction in greenhouse gases from coal substitution would be completely reversed.
Indirect land use change and related greenhouse gas emissions could occur when:
The numbers and references used to quantify the fuel chain emissions for woody biomass can be found on our 'Reference Manager'. The Fuel Chain Emissions documentation can be downloaded from here (will open in a new tab).