How do people make paper out of trees, and why not use something else?
By Beverly Law
Paper is an important part of modern life. People use it in school, at work, to make artwork and books, to wrap presents and much more. Trees are the most common ingredient for paper these days, but people have been taking notes and creating artworks for a very long time using lots of other kinds of surfaces and materials.
These people etched cuneiform and hieroglyph pictures that formed their languages into rock. They also wrote on slabs of wet clay, using a pen or brush made from a reed. Sometimes they baked these slabs hard in ovens to preserve them.
The Egyptians pioneered the first paper. Papyrus came from a 15-foot-tall (4.5 meter) plant of the same name that grew in marshlands along the Nile River. They cut the stalk into thin strips, pressed them together and dried them into the long rolls you can now see preserved in museums. They wrote in ink, which didn’t smudge or blur on this new paper. Papyrus made it easy to carry their writing with them in rolled up scrolls – much easier than carting around heavy clay tablets and rocks.
Wood tablets covered in beeswax became a popular writing material in Greece, Rome and Egypt. Children used them in school as you might use notebooks today. Heating the wax made it easy to erase the writing and reuse the tablets.
The Romans took the next step, making books with papyrus pages. Special manuscripts used pages made of treated calf skin.
It took Europeans another 800 years to finally start making paper. They cut up, soaked and treated linen and cotton rags. A half a century later, in 1690, the first rag-paper mill came to the American Colonies.
But as people used more and more paper, rags grew scarce. There were more trees than rags, so trees became the raw material. The first U.S. newspaper that was printed on paper made from ground-up wood was the Jan. 14, 1863, edition of the Boston Weekly Journal.
So how do people make paper out of trees today? Loggers cut trees, load them onto trucks and bring them to mills. Machines slice off the bark, and big wood chippers chop the logs into small bits. Those chips are boiled into a soup that looks like toothpaste. To get out any lumps, it is smashed flat, dried and cut up into sheets of paper.
The entire process, from planting a seedling to buying your school notebook, takes a very long time. Just growing the trees takes 10 to 20 years.
Making tons of paper from trees can harm the planet. Humans cut down 80,000 to 160,000 trees around the world every day, and use many of them to make paper. Some of those trees come from tree farms. But loggers also cut down forests for paper, which means that animals and birds lose their homes.
That’s why recycling is important. It saves a lot of trees, slows climate change and helps protect endangered animals, birds and all creatures that rely on forests for their homes and food.
Did you know that it takes 24 trees to make one ton of paper, which is about 200,000 sheets? You may use a piece of paper one or two times, but it can be recycled five to seven times. Recycling one ton of paper saves 17 trees. If it’s recycled seven times, it saves 117 trees.
So if paper isn’t good for the environment, why don’t people write on something else? The answer: They do. With computers, tablets and cellphones, people use much less paper than in the past. Maybe a day will come when we won’t use paper at all – or will save it for very special books and artworks.
Courtesy of The Conversation
Beverly LawProfessor Emeritus of Global Change Biology and Terrestrial Systems Science, Oregon State University
Beverly Law does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
For millennia, trees have provided mankind with fuel, food, fibre, and medicine from their fruit, flowers, roots, wood, leaves, and branches. In fact, many things we use daily are connected to wood. Printer paper, chewing gum, planks, viscose fabric, vitamins, pallets, toilet tissue, toothpaste, and detergents all have a link back to wood.
As a sustainably farmed resource that stores carbon, wood is increasingly being used not only in the built environment for houses and high-rises but also for its cellulose, lignin, and sugars. These elements all have a role in helping the world find renewable and low-carbon alternatives to the likes of plastic, chemicals, steel, and concrete.
The Paper Manufacturers Association of South Africa (PAMSA), its members, and its university partners are exploring the commercial potential of a range of products from the pulping and papermaking process, maximising product yield from each and every tree harvested.
“Two key advantages that commercially farmed trees bring are their renewability and their carbon storage,” explains Jane Molony, PAMSA executive director.
Kings of carbon capture
Trees in plantations are essentially crops that are planted and replanted in rotations, with only about 9% of the total tree count being harvested in any given year. “This means that there are always trees growing, at different stages of maturity, and these trees are all absorbing carbon dioxide (CO2) and storing the carbon,” says Molony.
“The fact that trees are planted, harvested, and replanted on the same land makes wood and paper a renewable and efficient resource,” Molony asserts. “For a low carbon future, it is tremendously exciting.”
With trees capturing more carbon from the atmosphere[i] than any other biome, they offer a means to mitigate the impact of climate change.
Paper itself is a biomaterial and one of the oldest technologies in the world. From chipping wood into small pieces, to cooking them to produce a soup-like slurry and then drying the fibres into sheets, papermaking is a complex and fascinating process. Companies are continually looking at every aspect of their operations to reduce water use, energy consumption and air emissions.
Papermakers are no longer restricted to manufacturing paper and cardboard boxes. South African companies can use their raw material to make bio-based products, chemicals, plastics, and fuels. Not only does this have an environmental and economic benefit, but it also opens up a whole new world for youngsters with an affinity for engineering, science, and innovation.
Low-carbon careers in the bio-economy
“Careers in pulp and paper technology and process engineering have not traditionally been sexy, but as the sector finds ways to diversify in the face of reduced printing and writing paper demand, chemists and chemical engineers can help discover the wonder of wood, wood-derived chemicals, and paper packaging,” notes Molony.
This includes the potential of forest residues (bark and branches), wood pulp, and paper mill waste to replace non-renewable materials such as plastics produced from oil or coal and other innovative products. Using their inherent biorefinery technologies, companies can extract a range of components such as cellulose, lignin, and sugars from process streams that would otherwise become process waste. “This takes mills beyond paper, and into the realms of a biorefinery,” Molony adds.
Natural polymers from planted trees
Cellulose – the most abundant organic compound and polymer on earth – is the major component of wood and the starting point for the various reactions.
Dissolving woodpulp, a purified form of cellulose, is suitable for subsequent chemical conversion into a range of products – it is spun into viscose and lyocell textile fibres for use in fashion and decorating textiles, cast into a film or regenerated into a sponge.
Wood also gives us products such as carboxymethyl cellulose or microcrystalline cellulose (MCC).
This fine powder is extremely versatile. It can bind active medicinal ingredients or vitamins into palatable tablets, stabilise emulsions or increase viscosity – which is why cellulose is added to low-fat yoghurt, and lipstick! It also acts as an abrasive or exfoliant in cosmetics or an anti-caking agent in washing powders or foods.
“It is a misconception that ‘sawdust’ is added to food. MCC is an approved and safe food additive that passes through our bodies, unabsorbed,” confirms Molony.
Tiny fibres with huge potential
Nanocellulose – tiny cellulose nanofibres (CNF) and nanocrystalline cellulose (NCC or CNC) – can be used in wound dressings and surgical gels, food supplements and edible packaging, or even as a composite for screens on electronic devices.
Tipped to be a rival to high-strength materials like Kevlar, nanocellulose composites have strength, barrier and performance attributes similar to, if not better than, carbon fibre. This makes them ideal for use in the automotive and aviation sectors.
Paper and paper packaging manufacturers are looking at ways to use nanocellulose to reduce the weight of paperboard without lowering strength and performance. The substance can also be applied as a recycling-friendly barrier coating instead of plastic.
Lighter footprints with lignin
Lignin is the glue that holds wood and plant fibres together. It is removed during the pulping process when manufacturing fine paper to prevent yellowing with age, with some 50-million tonnes being produced worldwide each year. Depending on the pulping process used, lignin can be recovered from the spent pulping liquors in different forms, i.e., lignin and lignosulphonates, or used as pellets for fuel.
Commercialisation of these lignin-based compounds creates opportunities in market segments outside of pulp and paper. Lignosulphonates are used in mining and road maintenance as a dust suppressant while their addition to ready-mix concrete improves the flow of concrete as well as reducing the water required, without compromising on strength. One of PAMSA’s members is the world’s largest producer of lignosulphonates from its South African and European operations.
Lignin also shows promise as a multifunctional and renewable alternative to petroleum-derived styrene plastics and foams.
Bio-chemicals from green gold
A substitute for diesel, bio-oils are one product obtained by heating wood in an oxygen-free environment, in a process known as pyrolysis. The solid product generated (bio-char) can be used as an enriched growing medium for seedlings or converted into high-grade activated carbon.
When wood waste is broken down by enzymes and fermentation, bio-ethanol is produced.
Furfural[ii], dubbed ‘the sleeping beauty of bio-renewable chemicals’, was one of the first bio-chemicals made from biomass. As a worthy competitor to oil-based chemicals, new interest has been sparked in furfural for the production of bio-fuels and bio-chemicals.
Furfural and its derivatives have been extensively used in the plastics, pharmaceutical and agrochemical industries. As a natural precursor to a range of chemicals and solvents, it is widely applied in fungicides and nematicides, transportation fuels, lubricants, resins, a rapid all-weather repair system for potholes and also for wood modification and book preservation. And that’s just the short list.
Cellulose and hemicellulose are complex carbohydrates (polysaccharides) rich in various sugar monomers (building blocks of more complex molecules) which can be extracted during the pulping process.
Xylitol is a natural sugar substitute that can be made from xylose, the sugar molecule in hemicellulose. It also has oral health benefits due to its acid neutralising and antibacterial properties and is commonly used in chewing gum. Work to commercialise the manufacture of xylitol in South Africa is already being done by a PAMSA member, and as local demand picks up for these products, other South African mills will be poised to start production.
Sawdust and bark can yield high-value speciality chemicals and composites while paper sludge can potentially be converted into NCC, bio-polymers and bio-gas. “We know that these products can be made from wood pulp, but studies are showing that we can also push mill waste streams towards new production channels, instead of landfill,” explains Molony.
Making the circular economy bigger
Work is being done by the South African pulp and paper industry through PAMSA’s Process Research Unit and the master’s student programme into biomass beneficiation such as the development of bio-based carbonate derivatives from lignin that can be used in the production of paper, glass and detergents, and exploring the commercial value of forest and mill residues.
By extracting more value from a tree, less goes to waste, Molony says. “This opens our sector up to make even more meaningful contributions to sustainable product development and sets up pulp and paper mills as biorefineries. This means we can improve our competitive advantage as a country, and offer innovative careers for young graduates.”
“Along with the significant contributions by members’ companies to research and development, PAMSA has partnerships with the universities of Pretoria, Witwatersrand, Stellenbosch, and the North West, as well as the support of the Department of Science and Innovation through the Sector Innovation Fund.”
Not only do pulp and paper production add around R3.8 billion annually to the South African economy, but the growing and harvesting of trees and the making and recycling of paper products also provide sustainable jobs for thousands of people.
And as a result, we keep removing carbon from the atmosphere by planting more trees.