Benefits and Downsides of Waste Paper Recycling

Both benefits and downsides of waste paper recycling have been debated multiple times.

Bajpai (2014) discussed the most important advantages of recycling paper.

• • Saving resources (wood, water, power): When secondary fibres are used in papermaking, the number of saved trees is about 17 per each tonne. Such additional resources as water and electricity for paper production are also preserved. The reason is that the biggest share of power that is used during the life cycle of paper is consumed at the stage of turning wood into paper. In general, the carbon footprint of paper produced from secondary fibres is up to 50% less compared to that produced from virgin fibres.
• • Decreasing of production emissions: The application of secondary fibres in papermaking contributes less to air pollution and water contaminating compared to wood processing. Bleaching step is not always necessary for the utilization of recycled fibres; however, even when it is needed, usually oxygen is used instead of chlorine. This reduces the amount of dioxins that are released into environment as a by-product of the chlorine bleaching process.
• • Saving soil from landfills: Nowadays, the landfills’ area is enormous with about 20-30% of space for waste paper. Recycling this waste will reduce landfill area. A landfill space of 2.3 in' is saved for every tonne of paper used for recycling.
• • Positive image for enterprises: Business can promote a positive company image by launching and maintaining a paper recycling programme. A number of corporations are using recycled paper in offices, even though the price of recycled paper is never lower when compared with that of regular paper. This can only be possible as a result of the public attitude to resources and environments.
• • Decreasing of transport emissions: Since waste paper is usually collected rather close to recycling facilities, the production of recycled paper reduces transportation footprint and economic expenses. That is why the life cycle of paper becomes more efficient.

However, the recycling of waste paper has not only the benefits but downsides as well. Since recycling process is a production, it also has its own carbon footprint. There are no completely ‘clean’ technologies with zero waste in the world. Recycling mills produce such residuals as sludge, including ink, adhesives, unusable fibres and other substances removed from the usable fibres. On the other hand, if the paper was not recycled, those materials would still finish the life cycle in landfills or incinerators, while recycling mills have enlarged environment-friendly methods of handling sludge (Bajpai 2014).

Recycling of Waste Paper

The recycling of waste paper has a long history. The first known effort to use waste paper for processing was made in 1567.

Background Information on Waste Paper and Cardboard: Composition of Paper and Cardboard

In order to consider what waste paper is recycled for and how it is processed, we present here a basic understanding of the composition and distribution of the main components in waste paper.

Paper and cardboard are one- or multilayer sheets that consist of cellulose fibres with the addition of various chemicals that are used to improve the properties such as opacity, brightness, or glossiness of the sheets. The most common additives, namely limestone (calcium carbonate, CaCO,), clay (kaolin, kaolinite, Al,Si,0₅(0H)₄), and starch have the largest proportion in the paper content. Their total weight is near 15%, though, the amount depends on the type of paper. Other chemicals, for example, resins, wet strength agents, optical brightening agents, sizing agents, dyestuffs, coatings, retention agents, anti-foaming agents, cleaning agents, and biocides are added to paper sheets in smaller amounts (up to 2 wt.% altogether) for the purpose of obtaining the specific properties of the final product. Finally, there are a few chemicals that may be found in paper in trace quantities, for instance, talc and sodium silicate that are residuals from the deinking procedure.

The structural difference of cardboard from paper is that cellulose fibres are set together in a stiffer way, it is thicker and less foldable. Cardboard has a larger density than paper and it is rarely single layer. As a rule, these are from two to four glued layers that are resistant to deformation and may exhibit barrier properties.

The source of cellulose for paper is usually wood; however, other plants, for example, cotton, rice, seaweed, etc. are also used in the production of paper. The main components of wood are natural polymers cellulose (approximately from 45 to 56 wt.%) and lignin (from 19 to 28 wt.%), at that the proportion of the components depends on the plant species. The function of lignin is holding together cellulose fibres, filling the space between the cell walls, and providing strength. Despite the crucial role in plants, lignin has no essential function in papermaking. Moreover, this component is undesirable since the progressive chemical degradation of lignin rapidly darkens the paper. On the other hand, when the life cycle of paper is short, for example, newsprint paper, or the whiteness is not important, such as corrugating cardboard or inner layers of multilayer sheets, a certain amount of lignin is permissible.

Difference between Virgin Fibres and Waste Paper and How to Solve Problems Related to the Complexity of Paper and Paper Recycling

There is a fundamental difference between virgin fibres in paper and fibres obtained from waste paper. Paper can be recycled only a certain number of times (from 3 to 5 times), the only drawback being a progressive shortening of cellulose fibres through processing, which reduces the strength of the resulting paper (Villanueva Krzyzaniak and Eder 2011). In other words, fibres are damaged during the papermaking operation. The fibres collapse during drying on the paper machine and there is hornifica- tion at the surface, so that the properties of the fibres are changed, with more fines produced (Technology of paper recycling 1995). When paper is recycled, it is turned into lower grade paper; for instance, white office paper becomes newsprint paper.

while paperboard reduces to sanitary paper. For the time of paper to paper recycling, the maximum obtainable yield is about 65%. This can give rise to large quantities of waste fibres not suitable for recycling; therefore, this has become a thing of concern to paper manufacturers (Ikeda et al. 2006).