Material of the month: Paper

Materials World magazine
,
2 Apr 2014
Trees

It is one of the oldest man-made materials still in extensive use
today, and the facilitator for momentous advances in information
storage, communication and education. But in this digital age, is paper
on the demise? Anna Ploszajski investigates.

The earliest material resembling paper is papyrus, made from the papyrus
plant, which was first produced in Egypt 6,000 years ago. Four thousand
years later, papyrus scrolls were replaced by parchment and vellum,
which were manufactured into book-like codices from dried animal skins.
Although papyrus was cheap and easy to produce, its sensitivity to
moisture limited its quality and utility, making these codices far
preferable to papyrus scrolls.

Meanwhile, 2,200 years ago, the ancient Chinese were starting to
manufacture paper from wood pulp. This gradually spread to the west via
the Silk Road. The first paper manufacturers in Europe were Muslims
living in what is today Portugal, Spain and Sicily, 1,000 years ago. The
technique extended to Italy and France, eventually spreading throughout
Germany by 1400.

Two major technological breakthroughs came in the use of waterpower,
which mechanised paper production, and the invention of the printing
press in 1453, kick-starting the printing revolution. According to
Francis Bacon, the printing press changed the face of the world. It
allowed rapid and accurate data storage and communication. Suddenly,
information could be freely disseminated, which encouraged a dramatic
increase in literacy, empowering the emerging middle classes. Although
initially religious in content, more and more secular books were
printed, which particularly benefited scientists in Europe, accelerating
the advancement of collective knowledge. The impact on the scientific
revolution, the Age of Enlightenment and the Protestant Reformation
cannot be underestimated.

Fast-forward 400 years and paper is used in an enormous range of diverse
applications, from a representation of value in the form of banknotes,
cheques, tickets and vouchers to the domestic setting, where its uses
range from toilet tissue to paper plates and food packaging. For a short
time during the 1960s in the USA, paper was even used as a novelty
fashion item. What started as a marketing stunt for Scott Paper Company
in 1966, dresses made from disposable cellulose material, soon became a
fashion craze. It was followed by everything from underwear and
children’s pinafores to raincoats and bikinis. However, the novelty soon
wore off, since the clothes were ill-fitting and uncomfortable, and by
1968 they had disappeared from the market. Today, cellulose-based fibres
are only used for disposable garments such as hospital gowns and
scrubs.

Pulp, paper’s woody precursor, is made by chemically separating lignin
from cellulose fibres sourced from trees. The most common chemical
pulping process used today is the kraft process, which dates back to the
1890s. In this process, wood chips are mixed with sodium hydroxide and
sodium sulphide to break the bonds between lignin and cellulose fibres.
This produces useful heat, which in some cases can make paper production
net energy positive, by running a generator connected to the electrical
grid or an adjacent paper mill. The process also recovers and reuses
all the inorganic chemical reagents. The pulp is then pressed and dried
until it contains less than 6% moisture. Finally, the paper is coated
with a thin layer of calcium carbonate or China clay and polished by
calendaring to produce a range of matt, silk and gloss effects.
Subsequent rollers produce textural finishes or watermarks, or use wire
patterns to imitate hand-made paper. Finished sheets are cut and loaded
onto reels for use in printing presses.

Finding a new use
At the end of its life, paper can be recycled by turning it back into
pulp and repeating the production process. The paper is mixed with
water, and a mechanical action separates the fibres by breaking the
hydrogen bonds that bind them together. Recycled paper fibres are mixed
with virgin pulp to maintain quality, although recycled products are
generally lower quality than paper made exclusively from virgin pulp.
Recycled paper fibres come from three main sources – substandard paper
produced in a mill that cannot be sold, off-cuts from shaping processes
and waste paper recycled by consumers. Paper fibres can be recycled
around seven times before the fibres become too degraded for it to be
used again. According to The Confederation of Paper Industries, paper is
the most recycled product in the UK, where more than 70% of the fibres
used to make paper are from recycled sources. In fact, the UK collects
more recyclable consumer waste than it can process, so the excess is
exported to Europe and Asia to assist with sustaining the global paper
industry. In 2012, 4.5 million tonnes of paper and cardboard were
exported for recycling.

Despite the huge uptake of paper recycling, the sustainability of the
industry is a controversial topic. The Paper Manufacturers Association
of South Africa estimates that, without operation of the paper industry
over the last 150 years, atmospheric CO2 levels would be around 5%
higher than they are today, owing to the carbon capture and
sequestration by the source forests. However, deforestation and, most
significantly, paper-based landfill make the overall paper cycle a net
contributor to global warming. When paper degrades anaerobically in
landfill sites, it releases methane, a potent greenhouse gas. This means
that for a comparison of landfill-based greenhouse gas emissions alone,
paper bags are as damaging to the environment as their plastic
counterparts.

Innovation in paper packaging

Paper must be one of the most influential, highimpact and enduring
materials in history. However, the dawning of the technological age
brings its longevity into question. The email has already replaced the
letter and the memo. So how long will it be before the Kindle replaces
the book, tablets replace newspapers and contactless payment replaces
cash? The survival of the industry will rely on innovation and the
development of competitive new technologies.

A good example of such innovation is in paper packaging. Smart paper
packaging with radio frequency identification can improve supply chain
traceability and safety for meat and pharmaceutical products. Such
products can be tracked in real-time, helping to streamline deliveries
and warehouse operations. Moulded paper containers thermoformed from
recycled fibre are one of the most sustainable packaging materials
available today, and are strong, lightweight and can be given attractive
finishes. Paper-based composite milk bottles boast superior
recyclability and biodegradability credentials, requiring just 0.5% of
the plastic used in conventional bottles. These next-generation
paper-based products will be able to secure the paper industry’s future
in terms of demand.

If it can become fully cyclic by further improving recycling processes,
paper stands a good chance of becoming a truly sustainable and
invaluable material. However, this is only possible if consumers take
responsibility for reducing the damaging methane release from paper in
landfill. Give some thought to where your Materials World will end up
this month – the pages of someone else’s newspaper next month or the
landfill site down the road – and you could be decreasing your carbon
footprint more than you think.