- Green Technology
Behind The Scene: Paper Recycling
Recycling of paper is carried out in a multi-stage process involving sorting, collection, transportation, storage, re-pulping, cleaning, laundering and finally conversion into paper.
The various stages of the process are described as under:
Sorting & Transportation
Usually sorting is the first stage of the entire paper recycling process. Basic sorting takes place at the household or office level. Paper is segregated from trash or other wastes such as plastic, metal, food and so on. Whenever proper separation of paper and other wastes is not feasible, it has to be turned into compost or used for landfills.
Recycling centers further sort the paper by grade or type of paper. For example, newspapers and corrugated boxes are sorted and handled separately.
Recyclable and segregated paper is often collected by waste paper dealers or recycling centres from our homes or offices. The collected paper is wrapped in tight bales and transported to the nearest waste paper dump. Paper collected from numerous households and offices is then taken together to the paper mill for recycling.
The collected paper is unloaded and kept in warehouses for storage. Paper mill workers also check and ensure that it has no other trash in it and sorting has been done as per the grade of the paper. This is important as the paper mill uses different grades of recovered paper to make different types of recycled paper products.
When the recovered paper is ready to be recycled, forklifts move the paper from the warehouse to large conveyors, which carry the load to a ‘pulper’. A pulper is essentially a big vat, filled with water and chemicals.
The pulper chops the recovered paper into smaller pieces. The mixture is often heated to break the paper down into tiny strands of fibres or cellulose. The old paper finally turns into a fine mixture called pulp. The pulp is passed through a screening process to remove small contaminants like bits of plastic and glue.
The pulp is also cleaned by spinning it around in large cone-shaped cylinders. This process throws out impurities like staples and pins.
The pulp at times requires laundering or deinking to remove printing ink, glue residues and adhesives.
Paper mills frequently employ a mix of two deinking processes. Ink traces are rinsed from the pulp with water in a process called ‘washing’. Floatation is used to remove larger particles and glue residues or other stickies. The process uses air bubbles. The pulp is fed into a large vat called a ﬂoatation cell. Air and soap-like chemicals called ‘surfactants’ are injected into the vat containing the pulp. Ink and stickies loosen out, separate from the pulp and get stuck to the air bubbles. The inky air bubbles create froth at the top and are removed, leaving behind the clean pulp.
What scientific or technological improvements have contributed to making the recycling process easier or more effective?
As paper is made out of pulp and re-pulping is a relatively easy process, the recycling is now pretty effective. Re-cycling of paper is therefore common across countries. However, the recovery varies from country to country. USA, for example, is able to recover and recycle more than 50% of paper consumed.
The challenge lies in recovery of paper from households and offices in a relatively uncontaminated form. Quite often consumed paper is mixed with trash and disposed off. Such contamination is a major difficulty in recycling. Although recovery is still possible, it increases the cost of sorting and cleaning.
What are the limitations of science in this area? What are the scientific or technological difficulties in ensuring that a quality product is obtained at the end of the recycling process?
Recycling of the same paper cannot be done again and again. Paper fibres break down and degrade after each recycling and usually cannot be recycled beyond eight times. Degradation of fibres during recycling limits the number of times that a particular paper fibre can be recycled.
Paper mills have however found out a partial solution. They often add some good quality raw or waste fibres to the recycled pulp. It improves the quality and strength of the recycled product.
Does the recycling process produce any pollution? Are there any solutions to this? How does this compare with the pollution produced in the original manufacture of the material?
- Paper production emits considerable water and air pollution. Compared to production of plastic bags, paper bag manufacturing, for instance, causes 70 percent more air pollution and releases 50 times more water pollutants.
- Pollution in recycling is lesser. It also avoids or reduces felling of trees, which in turn benefits the environment. Recycling saves some natural forests. It also reduces the need for Conifer or Eucalyptus plantations, which are undertaken for paper production but damage the environment.
Discuss the societal factors involved in this issue.
How does recycling impact on the number and type of jobs in the economy?
Recycling has significant social implications. It supports, especially in under-developed or developing countries, a large number of people engaged in sorting, collection, transport and trade of recyclable materials. Recycling is beneficial, in particular, to the economically lower strata of society.
Is recycling a cost-effective process? What are the tax implications of recycling?
Whether recycling is cost effective depends on the cost and effort involved in sorting and collection of materials for recycling. The process can be very labour intensive and add to costs in developed countries unless the citizens or consumers are socially and environmentally conscious. To cite an example, collection cost is relatively lower in Japan where households are meticulous in sorting paper from other trash.
Tax implications vary from country to country. Some countries charge a reduced levy on recycled paper.
What are the environmental impacts of recycling?
Recycling is beneficial to environment. In case of paper, it first of all reduces the cutting of trees for pulp production. Each tree saved contributes to the processing of greenhouse gases in the atmosphere.
More importantly, it recycles waste that would otherwise clog our drainage or result in land-fills. Disposal of waste can become a major problem, especially in land-starved countries like Singapore.
How does recycling impact on people’s awareness of environmental issues?
Recycling is a community initiative. When children see paper being collected from their homes for recycling, they become aware of the environmental issues from childhood. They become conscious and help in proper sorting and disposal of waste.
How widespread is the practice of recycling? What are the difficulties in establishing a recycling program in a particular geographical region?
The practice of recycling is widespread and further spreading. In some countries like USA and Japan, amount of paper recycled is huge. Normally, it is difficult to implement recycling programs in under-developed regions with lower literacy rates.