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Sustainability of Municipal Solid Waste Management
high yield that ranges from about 92 to 96%, and has high bulk, stiffness,
opacity, and softness. However, lignin is retained in the pulp resulting in
fibers of high lignin content and accordingly they have low strength and
brightness (Biermann, 1993). This pulp is generally used for the making of
newspapers, books, and magazines. The use of mechanical pulping is increas-
ing worldwide due to the high yield of the process as well as the increasing
competition for fiber resources.

Kraft (chemical) pulping
The word “kraft” means strong. Kraft pulping is one of a number of different
chemical pulping methods; it uses sodium hydroxide and sodium sulfide at
certain temperatures and pressures to dissolve the lignin of wood fibers and
produce pulp. It is useful for any wood species and gives a high strength pulp
characterized by long and strong fibers. This method is used to produce bags,
wrappings, linerboards, and bleached pulps for white papers.

Paper making and recycling
Paper can be produced from wood pulp or from non-wood fibers. Most devel-
oping countries do not have enough wood for producing pulp to be processed
for paper manufacturing and accordingly they use non-wood raw material
from agricultural residues for pulping. Examples of non-wood raw materials
are wheat straw, rice straw, and bagasse. Caustic pulping is used for non-
wood raw materials in order to dissolve the non-cellulose organic fraction
such as lignin, and leave behind the fibrous residual as pulp for paper pro-
duction. The process steps for rice straw pulping start by shredding the rice
straw material and cleaning it with water. The shredded fibers are then
cooked in a rotatory digester for dissolving the lignin content while leaving
the cellulose fibers. Vacuum filters are then used to separate the fibers from
the cooking liquor. Fibers are then thickened by centrifuges and finally
bleached by chlorination producing pulp ready to be used for paper manu-
facturing (Nour, 2002).
In Egypt, recycling paper is very important as it is estimated that Cairo
produces 8,000 ton/day of municipal solid waste, 10% of which is paper and
paperboard. The main objective of the recycling process is to reduce the
amount of solid waste present as well as to recover some of the primary
materials. Most of the papers that are used for newspapers or for educational
text books are being imported to all developing countries including Egypt,
which explains the marked increase in the price of press and publication in
general. This crisis occurred during 1995 when the imported newspaper
prices increased in Egypt and other developing countries by 40%. This will
not only affect the press and publication costs but also the educational sys-
tem where most of the government text books depend on this type of
imported paper. This clearly shows the importance of implementing recy-
cling in Egypt and other developing countries. It is also argued that by applying