Economic Issues of Biomass Energy Conversion - Biomass Gasification, Pyrolysis and Torrefaction - page 31

Primary biomass resources are categorized into two main types: virgin
biomass and waste biomass. Virgin or fresh biomass is available as it grows,
but secondary or waste biomass being a derived product is not available
immediately. For example, an old piece of furniture in a municipality landfill
site may have been in use for 20

50 years after the wood it was made of
grew in the forest. Some species of aquatic biomass are also good sources of
virgin biomass. These have higher net organic yields compared to most ter-
restrial biomass and have high growth rate. Table 2.1 gives values of poten-
tial growth rate of some aquatic biomass. Biomass being a renewable
resource its growth or replacement rate is an important parameter in avail-
ability assessment.
The production of biomass depends primarily on the land availability
and the climatic condition. Collection of data from the field level is impor-
tant to estimate the available land areas. Analysis of historical data is needed
to identify trends of land use pattern. This enables predictions for future
resource potential. Biomass yields vary with type, species of the plant, agro-
climatic region, rainfall, and other factors like irrigation and degree of
mechanization. Information on these factors is required to assess the land
resource and then to estimate the possible supply of biomass. The availabil-
ity of biomass is also restricted by accessibility constrains. Cultivable land
may be available, but physical difficulties in harvesting, collecting, and
transporting from the point of production to the plant may render that bio-
mass useless.
Main issues in biomass resource assessment are as follows:

Availability of forest or suitable lands for cultivation.

Net crop yields (for cultivated biomass).

Energy cost for cultivation as well as the price the market would pay for
the biomass.

TABLE 2.1 Growth Rate of Some Aquatic Biomass Expressed in Dry Tons

per Hectare per Year

Biomass Species Annual Growth Rate

Spartina alterniflora (in salt water) 33 dry ton/ha year

Giant Cane (Arundo donax), bulrush (Scirpus
lacustris)—fresh water swamp

57 59 ton/ha year

Cattail (Typha spp.)—a wetland biomass 25 30 dry ton/ha year

Water hyacinth (Eichhornia crassipes)—fresh water 150 ton/ha year

Chlorella (algae in lake, ponds, etc.) B 360 dry ton/ha year

Source: Data compiled from Klass (1998).