Energy Content
The potential energy value of biomass materials is determined by its chemical composition and is measured as Joules of energy in 1 g of fuel (J/g). For convenience this measure is usually expressed as MJ/kg or GJ/t. However, for practical matters the volume-related energy density is a much more important parameter considering the packaging of energy materials, ie. chips vs. sawdust vs. logs.
While the energy value of solid biomass has relatively low variation, the volume of a single unit of fuel equivalent can easily vary by a factor of ten, depending on the method of harvesting or processing. In the case of chipped forest and agricultural biomass, the application of densification technologies can considerably reduce the volume of space required for storage, thus increasing the energy density of the materials.
The total amount of energy released from fuel is called the heating value. Due to differences in chemical composition, softwoods have higher heating values than hardwoods, branches have higher heating values than stemwood, and bark and foilage have higher heating values than wood in general despite the higher ash and heavy metal content (Nurmi 1993). The approximate heating values of wood and various wood residues are shown in the table below (Corder 1976).
Encyclopedia ID: p1256
