A fuel of convenience
By Jackie Jones
Why pellets are packing the power
Suddenly, it seems, everyone is talking about pellets. The time certainly seems right for this rapidly growing branch of the biomass sector. High oil prices make pellets an increasingly attractive option for domestic and district heating, while the coal-power generation sector, especially in Europe, is keen to reduce its carbon emissions and try shifting towards co-firing with pellets. Meanwhile research is underway into manufacturing 'agropellets' from a wider range of agricultural residue and energy crops. Jackie Jones reports.
'It is quite possible that total pellet consumption in Europe will triple in the coming five years.'This is the view presented by Matti Hilli, CEO one of the world's largest pellet producers - Vapo Oy - speaking at the Bioenergy in Wood Industry 2005 conference, held in Finland last September.While growth in medium-sized district heating plants was steady, there was a marked increase in the co-firing of pellets with coal. On the home heating front, 2005 was a boom year for pellets in Germany, and as the likelihood of a European directive on renewable heating and cooling increases, that trend seems set to continue. Meanwhile, in industry, pellets are also being adopted as a source of on-site heat, often in CHP installations.
Compared with wood chip, for example, wood pellets are highly sophisticated form of packaged energy. First, their energy density is about four times that of good quality wood chip - about 3100 kWh/m3, meaning that their storage and transport is considerably easier and more efficient.And unlike briquettes, the other compacted wood fuel, pellets can be bulk handled like a liquid, as they are small enough to flow freely.
This means that they can be transported by tanker and 'pumped' into storage bins, then fed automatically into boilers.
Typically, wood pellets have a moisture content of only 6%-9% yielding advantages of increased combustability, reduced bulk and weight, and a greatly enhanced 'shelf-life'.At these levels of moisture, the fuel is not open to attack by mildew or other fungal spores, nor will microbial decomposition take place. Essentially the wood fuel becomes an easily transportable, and internationally tradeable commodity, which can be used just as readily in a pellet stove in a living room as in a power plant.
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