Noted: “Simply put, it takes about twice as much biomass to replace an equivalent weight of coal,” says Ken Ragland, UW-Madison emeritus mechanical engineering professor. Coal contains roughly 12,000 British thermal units of heat per pound, while dry biomass has about 6,000 to 9,000.
But energy yield is hardly the only consideration, he adds. “You also have to think about the moisture content. Biomass doesnâ??t start out dry â?? a green tree is half water.”