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Concerning slash in our forests, the economics are largely site specific. As Professor Boston mentioned yesterday, the slope of the ground, road access, size and amount of biomass collected all have impacts on whether or not it is profitable to collect it for use in a facility like ours. The biomass fuel market is also important. A year ago biomass prices were about 40-50% higher than they are today, due to the fact that the economy is suffering, spot market electricity prices are lower, and overall consumption has decreased. At last year's prices it absolutely made sense to put more effort into collecting available slash, while today it makes less sense.
As for using slash for pellets, it's a trickier poposition. In order to make pellets the wood used has to be clean, small, and have less than a 6-8% moisture content. Typically, sawdust and shavings from lumber operations have supplied the majority of the material for pellet manufacture. Green wood from the forests can range between 30-70% moisture content on a wet basis (depending on the time of year and how long it has been sitting), which would mean that any material used for pellet manufacturing has to be dried in some fashion, which would also mean emissions from drying facilities. Our biomass boiler operates at a fuel moisture content range of 40-60%, which allows us to use green wood, and in wet months a portion of supply from ground pallets or construction debris helps to bring overall moisture content down to reasonable levels. Anything over about 65% MC, and it takes all of the energy from the wood just to get the water out of it.
A distinction has to be made between different types of biomass for different uses as well. We can't burn yard trimmings or leaves, since the MC is higher than is beneficial to burn. These products largely go into composting operations where they can be used in gardens or yards as a substitute for bark dust.
posted 3 years, 11 months ago
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