The Important Paper Mill
A paper mill is a type of factory that makes paper from wood pulp
and other special ingredients. This is accomplished through a variety
of special machines, including a tree chipper, a digester, and a
Fourdrinier machine. Due to the Kraft process used to separate the
lignin from the plant products used in the paper making process
resulting in a sulfur byproduct, paper mills are associated with
The History of Paper Mills
The first known operating paper mill was in operation in 794 in
Baghdad. From here, the technology spread to Europe. Today, paper
mills use great amounts of water, energy, and wood and follow a
complex process in order to produce paper. These modern machines
are as much as 500 feet in length and move at speeds of over 100
mph, which makes them capable of producing sheets of paper as much
as 400 inches wide.
The Fully-Integrated Paper Mill Versus Non-Integrated Paper
A fully-integrated paper mill is one that receives forest logs
or wood chips and processes them to the individual fiber level.
The fully-integrated paper mill processes this fiber to a 4% pulp
slurry, which is then made into a sheet of paper.
Non-integrated paper mills, on the other hand, purchase the pulp
slurry after it has already been created at a pulp mill. When this
is done, the pulp slurry is purchased and transported in a dried
and baled form, which is called market pulp. These bales are rehydrated
with into a 4% solution before processed into sheets of paper.
The Smell of Paper Mills
The undesirable smell associated with paper mills only occurs if
the mill is also a pulp mill. In some cases, mills focus on only
pulp processing or paper processing. All of the major mills, however,
engage in both processes. The offensive smell is caused by the cooking
process used to soften the pulp in order to form it into paper.
Despite the bad smells they emit, the airborne particles are not
harmful to a persons health.
Making Wood Pulp
Wood pulp is the most common ingredient used to make paper. The
timber used to make wood pulp is generally called pulpwood and comes
from softwood trees, such as fir, spruce, pine, hemlock, and larch.
Hardwood tree such as birch and eucalyptus, however, are also used.
To make wood
pulp, the bark must first be removed from the wood. This can
be done with the help of water, called water stripping, though it
is not always necessarily done this way. Usually, the stripped bark
is used as fuel later in the paper making process.
The cellulose fibers that naturally occur in the wood are separated
using one of six methods. One choice is to use crush the wood with
grinders and to soak them in water in order produce what is called
groundwood. This pulp is often used for products requiring less
strength, such as paperboards and newsprint. The wood can also be
crushed with refiners, which use high pressure steam and temperatures
to created what is called thermomechanical pulp. Along with the
refiners, some chemicals can also be added to help separate the
cellulose from the wood. This produces what is called chemithermomechanical
pulp. All three of these forms are considered to be types of mechanical
pulp, which means they will turn yellow over time because the lignin
is not completely removed.
When wood chips are combined with chemicals inside a digester in
order to break down the cellulose, it produces what is known as
a chemical pulp. The heat and chemicals inside the digester causes
the lignin to dissolve without breaking down the wood fibers. The
liquid byproduct containing the lignin is dried and used as a fuel
and the paper product created from chemical pulp is used in materials
needing to be stronger.
Recycled pulp can also be created from waster paperboard and paper.
This pulp does not require as extensive of a process because the
cellulose has already been removed. This pulp is usually used to
make newsprint, paperboard, and sanitary paper.
Biological pulping is another form of pulping that is currently
being researched. This process is similar to chemical pulping, but
utilizes a fungi to break down the lignin rather than chemicals.
The potential environmental benefits of this type of pulping are
After the pulp is produced, it is bleached in order to create white
paper. The chemicals that have been used in this process have caused
environmental concerns. Therefore, the pulp industry has been using
chlorine alternatives, such as hydrogen peroxide, oxygen, and ozone.
After being bleached, the pulp is moved through the Fourdrinier
machine where it is dried and shaped.
The paper mill industry is a multi-billion dollar industry with
a large impact on the economy
in the United States, yet most people are largely unaware paper
mills and their role in our society.