Densified biomass: a new form of solid fuel

Abstract

Biomass is an economically and environmentally attractive fuel, but it is often difficult to collect, store, ship, and use. Densifying biomass to a specific gravity of 1.0 eliminates most of these fundamental problems and produces a uniform, clean, stable fuel: densified biomass fuel or DBF. Before conversion to DBF, raw biomass residues generally require preparation: the separation of noncombustibles from combustibles, expecially for solid municipal waste; milling; and drying. About 5% of the energy content in raw biomass can be expended in preparation and 1% to 3% in densification. In its densified form, biomass can be burned in standard equipment with reduced emissions and increased heat release and thermal efficiency. Tests have shown that DBF is an acceptable substitute or diluent in existing coal-fired systems. In addition, DBF may be used in home heating, pyrolysis, gasification, and power generation. Based on component equipment costs and the installed cost of existing plants, the estimated break-even selling price of Woodex pellets is $1.20 to $3.40/MBtu or $19.20 to $54.40/ton, depending on feedstock cost. Within that cost range, DBF appears to be economically competitive with coal in some markets, particularly when taking into account environmental advantages of low sulfur content. Even when forestmore » and farm residues are available for fuel purposes, it may be preferable to pellet the residues, rather than combust them directly, because of transportation, storage, and capital investment savings.« less

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