Экология сегодня. Макеева М.Н - 45 стр.

UptoLike

ВУЗ: 

ТГТУ | Тамбов

Составители: 

Рубрика: 

with rags) and manufacturers began searching for alternatives. Yet, it was not until 1843 that ground-wood (or
pulp) harvested from trees became the papermaker’s material of choice.
Today, the world consumes about 300 million tons of paper each year. Most of that paper is made from
virgin pulp, but recycled paper accounts for 38 % of the world’s total fiber supply and non-wood fibers from
plants like hemp or kenaf make up 7 %. The U.S., which contains only 5 % of the world’s population, uses
30 % of all paper. In that country, the forest and paper products industry generates $200 billion dollars in sales
every year, accounting for 7 % of the total manufacturing output of the United States. About 28 % of all wood-
cuts in the U.S. are used for papermaking and according to a 2000 report by PaperCom Alliance the demand for
paper worldwide has grown 30 % in the past 6 years and is projected to grow even more.
Having come a long way from using rags and mulberry bark, papermaking has become a sophisticated sci-
ence. Once a tree is cut down, it goes to a mill where it is debarked and then chipped into tiny fragments by a
series of whirling blades. These fragments are then "cooked" in a vat with water and several chemicals, includ-
ing caustic soda and sodium sulfate, to make gooey slurry known as pulp. In the final stages, additives such as
starch, China clay, talc and calcium carbonate, are added to the pulp to improve the strength and brightness of
the paper. Then the pulp is bleached to a white color using water and chlorine before being pressed into rolls
and dried.
Unfortunately, the paper making process is not a clean one. According to the U.S. Toxic Release Inventory
report published by the U.S. Environmental Protection Agency, pulp and paper mills are among the worst pol-
luters to air, water and land of any industry in the country. The Worldwatch Institute offers similar statistics for
the rest of the world. Each year millions of pounds of highly toxic chemicals such as toluene, methanol, chlo-
rine dioxide, hydrochloric acid, and formaldehyde are released into the air and water from paper making plants
around the world.
Paper making also uses up vast quantities of trees. But trees are a renewable resource, which means that
once one is cut down another can be planted in its place. In fact, much of the wood used by paper companies in
the U.S. comes from privately owned tree farms where forests are planted, groomed and thinned for harvest in
20 to 35 year cycles, depending on the tree species. Around the world, tree farms supply 16 % of all wood used
in the paper industry while the bulk comes from second growth forests. Only 9 % of the wood used to make pa-
per is harvested from old growth forests, which are impossible to replace because of their maturity.
Yet, while tree farms or plantations help feed the demand for wood, they cannot provide the plant and ani-
mal diversity found in natural forests. Plus, according to a 1996 report from the U.S. Forest Service, the rate of
harvest for softwood trees in the southern United States outpaced growth for the first time since 1953.
For these reasons, there is a growing chorus of entrepreneurs, environmentalists and inventors who are
coming up with ways to make paper without having to use as many chemicals or so many trees. Recycling is by
far the most common way to help save a tree. According to the Worldwatch Institute recycling efforts around
the world recovered about 110 million tons, or 43 %, of all paper used. About 45 % of all paper in the United
States was kept out of landfills in 1998 and almost all paper makers in the U.S. substitute some recycled paper
for virgin wood in the pulp making stage. Some paper mills rely on recycled waste as their primary source of
raw material.
Others point to agricultural waste as a stand in for wood. Agri-pulp, as it is called, is wheat, oat, barley and
other crop stalks left over after harvesting. Combined with recycled paper and other fillers, some paper makers
are finding that agri-pulp paper makes fine stationery.
Hemp is a wood substitute that has a rich history in the paper making industry from paper’s origins in
China in the first century AD to the Declaration of Independence, which was written in the 18th century on
hemp paper. Hemp is now used to make rope and clothes as well as paper. Unfortunately, it is illegal to grow
hemp in the U.S. because it is a non-intoxicating variety of cannabis sativa, the same plant marijuana comes
from. For that reason, hemp must be imported for use in the U.S.
Kenaf is also known as an excellent tree-substitute in making paper. This 4,000-year-old hibiscus plant –
an annual, non-wood fiber plant related to okra and cotton – is native to central Africa and can grow up to 18
feet tall in a four-to-five month season. Like hemp, kenaf is naturally whiter than wood and can be bleached
with hydrogen peroxide instead of chlorine.
One of the major reasons paper mills are hesitant to convert to using kenaf or hemp to make paper is be-
cause they are not set up to process anything except trees. Converting a paper mill to process these wood pulp
alternatives would cost tens of millions of dollars and major coordination with their suppliers and customers.
Still – like the conversion of radio to television as the major entertainment source in the 1950s and 1960s –
such a conversion from trees to non-wood source materials in the papermaking process can ultimately provide
extraordinary economics for the manufacturers and the consumers. It is simply a matter of the different groups

Страницы