Agriculture residues are another potential biomass feedstock
available in Pakistan for energy conversion. The term agricultural
residue is used to describe all the organic materials which are
produced as the by-products from harvesting and processing of
agricultural crops. These residues are further categorized into primary
residues and secondary residues. Agricultural residues, which
are generated in the field at the time of harvest, are defined as primary
or field based residues (e.g. rice straw and sugar cane tops),
whereas those co-produced during processing are called secondary
or processing based residues (e.g. rice husk and bagasse). Availability
of primary residues for energy application is usually low
since collection is difficult and they have other uses as fertilizer,
animal feed, etc. However secondary residues are usually available
in relatively large quantities at the processing site and may be
used as captive energy source for the same processing plant involving
no or little transportation and handling cost. Table 2 lists the
potential crops generating residues and their available quantity in
Pakistan.