In view of this thorough investigation, the authors offer a few
suggestions:
• The production of CRCU should begin with original industrial grade
urea granules rather than melting, transforming, dissolving or
polymerization to fabricate controlled release matrices with other
materials.
• Coating material should be selected with a view to its (i) affinity
with urea; (ii) its ability to permeate water and urea solution; (iii)
its capability to impede immediate urea escape from the coating
surface; and (iv) its ability to release urea in a manner that meets
a crop's metabolic requirements over a specified period of time. It
should also be biodegradable and cheaper. Apparently, no such
material(s) exist which possess these ideal traits. Nevertheless,
bio-composites based on starch/lignin/cellulose can indeed be
modified to significantly achieve such properties.
• The coating process should enable industrial production of CRCU
without changing the spherical geometry of urea granules. For this
reason, a fluidized bed coater, pan coater or rotary drum coater
may be employed. Due to its excellent heat and mass transfer
characteristics in addition to its easy operation, fluidized bed coating
is a good candidate for industrial scale production. However, bear in
mind thatwhen using the fluidized bed, coating materials should be
compatible with effortless spraying of the fluidized bed of urea
granules.