BIOLOGY-Concept of Biopulping
Concept
of Biopulping
Biopulping
is the treatment of wood chips and other lignocellulosic materials with natural
wood decay fungi prior to thermomechanical pulping.
Method
Wood
is debarked, chipped and screened according to normal mill operations. Then chips
are briefly steamed to reduce natural chip microorganisms, cooled with forced
air, and inoculated with the biopulping fungus. The inoculated chips are piled
and ventilated with filtered and humidified air for 1 to 4 weeks prior to
processing.
Advantages
of Biopulping
Reduced
electrical energy consumption (at least 30%) during mechanical pulping; potential
30% increase in mill through put for mechanical pulping; Improved paper
strength properties; Reduced pitch content and Reduced environmental impact.
Biobleaching of Paper
Involves the use of enzymes or whole organisms instead
of chemicals to carry out bleaching of paper Examples include
wo
processes such; elemental chlorine free
(ECF) and totally chlorine free (TCF) bleaching technologies.
Direct
removal of lignin or removal of xylan which binds lignin can be done
(i)
Pulp
can be bleached with white-rot fungi and their lignolytic enzymes, enabling
chemical savings to be achieved and the chlorine free bleaching process to be
established.
White
rot fungi produce extracellular oxidative enzymes, which initiate oxidation of
lignin. Due to their lignin degrading capacity, whole cultures of various white
rot fungi cause extensive brightness gains and delignification of kraft pulp.
MnP is considered to be the most important enzyme involved in kraft
biobleaching.
(ii)
Also
biological methods involving pulp pre-bleaching using xylanases provide the
possibility of selectively removing up to 20% of xylan from pulp and saving up
to 25% of chlorine containing bleaching chemicals.
Advantages
of Biobleaching
Reduced
consumption of bleaching chemical; reduced adsorbable organic halogen; improved
pulp and paper quality; improved brightness; reduced effluent toxicity and
pollution load.
SIZING
Sizing is used during paper manufacture in order to
reduce the paper's tendency when dry to absorb liquid, with the goal of
allowing inks and paints to remain on the surface of the paper, and to dry
there rather than be absorbed into the paper.
This is achieved by curbing the paper fibers' tendency to absorb
liquids by capillary action.
In addition, sizing affects abrasiveness, creasibility, finish, printability,
smoothness
